• Sinewave oscillator without gain control.

    From Edward Rawde@21:1/5 to All on Thu Jan 23 19:14:24 2025
    Before you can make a 1kHz sinewave oscillator with constant output level and better than 120dB harmonic distortion you'll need an
    oscillator which does better than that when it passes through the required output level.
    The circuit below was simulated in LTSpice 24.1.0 with all updates.
    There are reasons why I'm not sure I'd trust version 17.x of LTSpice to give the most accurate results but I haven't tested this
    circuit in any other version.
    After starting the simulation, wait until it has simulated about 7 seconds and then stop the simulation. Close the annoying log
    window which 24.1.0 will produce.
    You can now select a sample of about 100ms when it passes through 0dB (just under 2V) and run an FFT on it with Blackman-Harris
    window.
    This will show that this circuit is approaching 120dB down on harmonics.
    So if you want to do better than that then you'll need an oscillator circuit which has better performance to begin with. You can
    then add gain control for constant level.
    I've not so far found an oscillator circuit in LTSpice with better harmonic distortion performance than this one.
    You can, of course, try to use filtering to reduce the unwanted harmonics. Removing the first four harmonics produced by this
    circuit will get it approaching 130dB but don't ask me how that would be measured in reality or what it would cost to do so even if
    it can be measured.

    Version 4.1
    SHEET 1 2196 932
    WIRE 0 -416 0 -448
    WIRE 208 -288 48 -288
    WIRE 944 -288 848 -288
    WIRE 1136 -288 1008 -288
    WIRE 112 -208 112 -240
    WIRE 48 -192 48 -288
    WIRE 80 -192 48 -192
    WIRE 480 -192 416 -192
    WIRE 608 -192 544 -192
    WIRE 848 -192 848 -288
    WIRE 944 -192 848 -192
    WIRE 1136 -192 1136 -288
    WIRE 1136 -192 1024 -192
    WIRE 208 -176 208 -288
    WIRE 208 -176 144 -176
    WIRE 256 -176 208 -176
    WIRE 288 -176 256 -176
    WIRE 0 -160 0 -336
    WIRE 80 -160 0 -160
    WIRE -224 -144 -224 -240
    WIRE 0 -112 0 -160
    WIRE 0 -112 -64 -112
    WIRE 112 -112 112 -144
    WIRE 416 -96 416 -192
    WIRE 480 -96 416 -96
    WIRE 608 -96 608 -192
    WIRE 608 -96 560 -96
    WIRE 848 -96 848 -192
    WIRE 896 -96 848 -96
    WIRE 1008 -96 976 -96
    WIRE 1136 -96 1136 -192
    WIRE 1136 -96 1088 -96
    WIRE 0 -80 0 -112
    WIRE -64 -64 -64 -112
    WIRE 496 0 496 -16
    WIRE 416 16 416 -96
    WIRE 416 16 352 16
    WIRE 464 16 416 16
    WIRE 928 16 928 0
    WIRE 1136 16 1136 -96
    WIRE 1168 16 1136 16
    WIRE 1296 16 1248 16
    WIRE 1456 16 1360 16
    WIRE 1520 16 1456 16
    WIRE -224 32 -224 -64
    WIRE -64 32 -64 0
    WIRE 0 32 0 0
    WIRE 608 32 608 -96
    WIRE 608 32 528 32
    WIRE 640 32 608 32
    WIRE 720 32 704 32
    WIRE 848 32 848 -96
    WIRE 848 32 800 32
    WIRE 896 32 848 32
    WIRE 432 48 416 48
    WIRE 464 48 432 48
    WIRE 1136 48 1136 16
    WIRE 1136 48 960 48
    WIRE 864 64 848 64
    WIRE 896 64 864 64
    WIRE 496 80 496 64
    WIRE 1520 80 1520 16
    WIRE 928 96 928 80
    WIRE 1520 176 1520 160
    WIRE 352 224 352 16
    WIRE 480 224 352 224
    WIRE 640 224 560 224
    WIRE 1136 224 1136 48
    WIRE 1136 224 720 224
    FLAG 496 -16 V+
    FLAG 928 0 V+
    FLAG 1520 176 0
    FLAG 1456 16 output
    FLAG -224 32 0
    FLAG 496 80 0
    FLAG 928 96 0
    FLAG -224 -240 V+
    FLAG 432 48 half
    FLAG 864 64 half
    FLAG 112 -112 0
    FLAG 112 -240 V+
    FLAG 256 -176 half
    FLAG 0 32 0
    FLAG 0 -448 V+
    FLAG -64 32 0
    SYMBOL voltage -224 -160 R0
    WINDOW 123 0 0 Left 0
    WINDOW 39 10 135 Left 2
    WINDOW 0 10 0 Left 2
    WINDOW 3 15 104 Left 2
    SYMATTR InstName V2
    SYMATTR Value 32
    SYMBOL res 1040 -208 R90
    WINDOW 0 0 56 VBottom 2
    WINDOW 3 32 56 VTop 2
    SYMATTR InstName R9
    SYMATTR Value 15k
    SYMBOL res 816 16 R90
    WINDOW 0 0 56 VBottom 2
    WINDOW 3 32 56 VTop 2
    SYMATTR InstName R12
    SYMATTR Value 8.2K
    SYMBOL cap 1008 -304 R90
    WINDOW 0 0 32 VBottom 2
    WINDOW 3 32 32 VTop 2
    SYMATTR InstName C2
    SYMATTR Value 10n
    SYMATTR SpiceLine V=16 Irms=647m Rser=0.0322889 Lser=0 mfg="KEMET" pn="C0201C103K4PAC" type="X5R"
    SYMBOL cap 704 16 R90
    WINDOW 0 0 32 VBottom 2
    WINDOW 3 32 32 VTop 2
    SYMATTR InstName C4
    SYMATTR Value 22n
    SYMATTR SpiceLine V=4 Irms=356m Rser=0.150334 Lser=0 mfg="KEMET" pn="C0402C223K7PAC" type="X5R"
    SYMBOL res 576 -112 R90
    WINDOW 0 0 56 VBottom 2
    WINDOW 3 32 56 VTop 2
    SYMATTR InstName R13
    SYMATTR Value 10k
    SYMBOL cap 544 -208 R90
    WINDOW 0 0 32 VBottom 2
    WINDOW 3 32 32 VTop 2
    SYMATTR InstName C5
    SYMATTR Value 22p
    SYMATTR SpiceLine V=16 Irms=0 Rser=0.3482 Lser=551p mfg="Würth Elektronik" pn="885012006019 WCAP-CSGP 0603" type="NP0"
    SYMBOL res 736 208 R90
    WINDOW 0 0 56 VBottom 2
    WINDOW 3 32 56 VTop 2
    SYMATTR InstName R14
    SYMATTR Value 1388
    SYMBOL res 1264 0 R90
    WINDOW 0 -4 57 VBottom 2
    WINDOW 3 32 56 VTop 2
    SYMATTR InstName R7
    SYMATTR Value 600
    SYMBOL res 1536 176 R180
    WINDOW 0 47 75 Left 2
    WINDOW 3 36 40 Left 2
    SYMATTR InstName R8
    SYMATTR Value 600
    SYMBOL res -16 -320 M180
    WINDOW 0 40 70 Left 2
    WINDOW 3 37 41 Left 2
    SYMATTR InstName R5
    SYMATTR Value 100k
    SYMBOL res -16 16 M180
    WINDOW 0 40 70 Left 2
    WINDOW 3 38 43 Left 2
    SYMATTR InstName R10
    SYMATTR Value 100k
    SYMBOL cap -48 0 R180
    WINDOW 0 24 56 Left 2
    WINDOW 3 24 8 Left 2
    SYMATTR InstName C1
    SYMATTR Value 10n
    SYMATTR SpiceLine V=50 Irms=291m Rser=0.34258 Lser=0 mfg="KEMET" pn="C0805F103K5RAC" type="X7R"
    SYMBOL cap 1360 0 R90
    WINDOW 0 0 32 VBottom 2
    WINDOW 3 32 32 VTop 2
    SYMATTR InstName C6
    SYMATTR Value 10000n
    SYMATTR SpiceLine V=25 Irms=0 Rser=0 Lser=0 mfg="Murata" pn="GRM188R61E106MA73" type="X5R"
    SYMBOL res 992 -112 R90
    WINDOW 0 0 56 VBottom 2
    WINDOW 3 32 56 VTop 2
    SYMATTR InstName R11
    SYMATTR Value 150k
    SYMBOL res 576 208 R90
    WINDOW 0 0 56 VBottom 2
    WINDOW 3 32 56 VTop 2
    SYMATTR InstName R15
    SYMATTR Value 8.2k
    SYMBOL res 1104 -112 R90
    WINDOW 0 0 56 VBottom 2
    WINDOW 3 32 56 VTop 2
    SYMATTR InstName R16
    SYMATTR Value 47k
    SYMBOL OpAmps\\LT1058 112 -240 R0
    SYMATTR InstName U5
    SYMBOL OpAmps\\LT1678 928 48 R0
    SYMATTR InstName U3
    SYMBOL OpAmps\\LT1678 496 32 R0
    SYMATTR InstName U4
    TEXT -304 200 Left 2 !.tran 0 30 0 1u uic
    TEXT -304 152 Left 2 !.options plotwinsize=0 numdgt=7 method=trap
    TEXT -272 -568 Left 2 ;1kHz low distortion sinewave oscillator.
    TEXT -272 -536 Left 2 ;23 Jan 2025.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Bill Sloman@21:1/5 to Edward Rawde on Fri Jan 24 15:52:14 2025
    On 24/01/2025 11:14 am, Edward Rawde wrote:
    Before you can make a 1kHz sinewave oscillator with constant output level and better than 120dB harmonic distortion you'll need an
    oscillator which does better than that when it passes through the required output level.

    This is obviously true. Why do you think you need to tell us about it?

    The circuit below was simulated in LTSpice 24.1.0 with all updates.
    There are reasons why I'm not sure I'd trust version 17.x of LTSpice to give the most accurate results but I haven't tested this
    circuit in any other version.

    The accuracy of the results depends - first and foremost - on the
    accuracy of the Spice models. The only reason you could have to trust
    the LTSpice results would be that the real circuit gave the same results
    under the same conditions. John May has gone that far - you and I don't
    seem to have.

    After starting the simulation, wait until it has simulated about 7 seconds and then stop the simulation. Close the annoying log
    window which 24.1.0 will produce.
    You can now select a sample of about 100ms when it passes through 0dB (just under 2V) and run an FFT on it with Blackman-Harris
    window.

    But why bother?

    This will show that this circuit is approaching 120dB down on harmonics.

    For the circuit - as simulated. A real circuit will behave differently -
    it will have stray inductances and capacitances which are not include in
    the schematic and the device models merely approximate the actual
    performance of the device being modelled - mostly accurately enough for
    all practical purposes, but this map really isn't the territory.

    LTSpice simulations can be a reliable guide to what won't work. They are
    less reliable guides to ultimate performance.

    So if you want to do better than that then you'll need an oscillator circuit which has better performance to begin with. You can
    then add gain control for constant level.

    You do have to add gain control to get a constant output level, and you
    do have to do it without introducing too much extra distortion.

    I've not so far found an oscillator circuit in LTSpice with better harmonic distortion performance than this one.

    Who cares. The distortion levels we are quibbling about are in the same
    range as the rounding error in the Spice numerical integration.

    You can, of course, try to use filtering to reduce the unwanted harmonics. Removing the first four harmonics produced by this
    circuit will get it approaching 130dB but don't ask me how that would be measured in reality or what it would cost to do so even if
    it can be measured.

    You can get 20-bit A/D converters that sample quite fast enough to
    monitor a 1kHz oscillator, and you can do a Fourier transform on the
    stored output of the A/D. It wouldn't cost me any money because my
    current computer has an audio input that works that way, and some
    software from an old friend in Scotland that lets me use it as signal
    monitor. It would cost me time because I installed the software perhaps
    ten years ago and have only used it once.

    --
    Bill Sloman, Sydney

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Edward Rawde@21:1/5 to Bill Sloman on Fri Jan 24 01:02:37 2025
    "Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vmv6ac$22ufe$1@dont-email.me...
    On 24/01/2025 11:14 am, Edward Rawde wrote:
    Before you can make a 1kHz sinewave oscillator with constant output level and better than 120dB harmonic distortion you'll need
    an
    oscillator which does better than that when it passes through the required output level.

    This is obviously true. Why do you think you need to tell us about it?


    You do make me laugh sometimes Bill.
    Your circuit doesn't come anywhere close to 120dB but it does depend on which simulator you ask.
    Adding a FET gain stabilizer to the circuit I posted seems to have negligible effect on the distortion.
    So I'd concentrate on the oscillator distortion level rather than the gain controller contribution if I wanted to attempt better
    than 120dB.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From albert@spenarnc.xs4all.nl@21:1/5 to Edward Rawde on Fri Jan 24 12:40:17 2025
    In article <vmum11$n7g$1@nnrp.usenet.blueworldhosting.com>,
    Edward Rawde <invalid@invalid.invalid> wrote:
    <SNIP>
    This will show that this circuit is approaching 120dB down on harmonics.
    So if you want to do better than that then you'll need an oscillator
    circuit which has better performance to begin with. You can
    then add gain control for constant level.
    I've not so far found an oscillator circuit in LTSpice with better
    harmonic distortion performance than this one.
    You can, of course, try to use filtering to reduce the unwanted
    harmonics. Removing the first four harmonics produced by this
    circuit will get it approaching 130dB but don't ask me how that would be >measured in reality or what it would cost to do so even if
    it can be measured.

    If I read the specs on capacitors, I fear that even a passive filter
    would increase the distortion unless rigid air capacitors are used.
    Comment?
    In general:
    In how far are passive electronic components ideal, distortion free?
    (I read bad things about SMD capacitors.)

    Groetjes Albert
    --
    Temu exploits Christians: (Disclaimer, only 10 apostles)
    Last Supper Acrylic Suncatcher - 15Cm Round Stained Glass- Style Wall
    Art For Home, Office And Garden Decor - Perfect For Windows, Bars,
    And Gifts For Friends Family And Colleagues.

    --- SoupGate-Win32 v1.05
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  • From john larkin@21:1/5 to invalid@invalid.invalid on Fri Jan 24 09:14:53 2025
    On Thu, 23 Jan 2025 19:14:24 -0500, "Edward Rawde"
    <invalid@invalid.invalid> wrote:

    Before you can make a 1kHz sinewave oscillator with constant output level and better than 120dB harmonic distortion you'll need an
    oscillator which does better than that when it passes through the required output level.
    The circuit below was simulated in LTSpice 24.1.0 with all updates.
    There are reasons why I'm not sure I'd trust version 17.x of LTSpice to give the most accurate results but I haven't tested this
    circuit in any other version.
    After starting the simulation, wait until it has simulated about 7 seconds and then stop the simulation. Close the annoying log
    window which 24.1.0 will produce.
    You can now select a sample of about 100ms when it passes through 0dB (just under 2V) and run an FFT on it with Blackman-Harris
    window.
    This will show that this circuit is approaching 120dB down on harmonics.
    So if you want to do better than that then you'll need an oscillator circuit which has better performance to begin with. You can
    then add gain control for constant level.
    I've not so far found an oscillator circuit in LTSpice with better harmonic distortion performance than this one.
    You can, of course, try to use filtering to reduce the unwanted harmonics. Removing the first four harmonics produced by this
    circuit will get it approaching 130dB but don't ask me how that would be measured in reality or what it would cost to do so even if
    it can be measured.

    Open LT Spice and make a 1 KHz sinewave voltage source. Run for 10
    seconds and FFT. The 3rd harmonic is down 48 dB.

    So Spicing low distortion oscillators might not be an exercize in
    reality.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Edward Rawde@21:1/5 to Edward Rawde on Fri Jan 24 14:14:36 2025
    "Edward Rawde" <invalid@invalid.invalid> wrote in message news:vn0nco$1l9o$1@nnrp.usenet.blueworldhosting.com...
    "john larkin" <JL@gct.com> wrote in message news:jei7pjt2pc35osipchs2891gqtavk25a7k@4ax.com...
    On Thu, 23 Jan 2025 19:14:24 -0500, "Edward Rawde"
    <invalid@invalid.invalid> wrote:

    Before you can make a 1kHz sinewave oscillator with constant output level and better than 120dB harmonic distortion you'll need
    an
    oscillator which does better than that when it passes through the required output level.
    The circuit below was simulated in LTSpice 24.1.0 with all updates.
    There are reasons why I'm not sure I'd trust version 17.x of LTSpice to give the most accurate results but I haven't tested this
    circuit in any other version.
    After starting the simulation, wait until it has simulated about 7 seconds and then stop the simulation. Close the annoying log
    window which 24.1.0 will produce.
    You can now select a sample of about 100ms when it passes through 0dB (just under 2V) and run an FFT on it with Blackman-Harris
    window.
    This will show that this circuit is approaching 120dB down on harmonics. >>>So if you want to do better than that then you'll need an oscillator circuit which has better performance to begin with. You can
    then add gain control for constant level.
    I've not so far found an oscillator circuit in LTSpice with better harmonic distortion performance than this one.
    You can, of course, try to use filtering to reduce the unwanted harmonics. Removing the first four harmonics produced by this
    circuit will get it approaching 130dB but don't ask me how that would be measured in reality or what it would cost to do so even
    if
    it can be measured.

    Open LT Spice and make a 1 KHz sinewave voltage source. Run for 10
    seconds and FFT. The 3rd harmonic is down 48 dB.

    So Spicing low distortion oscillators might not be an exercize in
    reality.


    The following circuit was simulated in LTSpice 24.1.0 ...

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Edward Rawde@21:1/5 to john larkin on Fri Jan 24 13:49:58 2025
    "john larkin" <JL@gct.com> wrote in message news:jei7pjt2pc35osipchs2891gqtavk25a7k@4ax.com...
    On Thu, 23 Jan 2025 19:14:24 -0500, "Edward Rawde"
    <invalid@invalid.invalid> wrote:

    Before you can make a 1kHz sinewave oscillator with constant output level and better than 120dB harmonic distortion you'll need an
    oscillator which does better than that when it passes through the required output level.
    The circuit below was simulated in LTSpice 24.1.0 with all updates.
    There are reasons why I'm not sure I'd trust version 17.x of LTSpice to give the most accurate results but I haven't tested this
    circuit in any other version.
    After starting the simulation, wait until it has simulated about 7 seconds and then stop the simulation. Close the annoying log
    window which 24.1.0 will produce.
    You can now select a sample of about 100ms when it passes through 0dB (just under 2V) and run an FFT on it with Blackman-Harris
    window.
    This will show that this circuit is approaching 120dB down on harmonics.
    So if you want to do better than that then you'll need an oscillator circuit which has better performance to begin with. You can
    then add gain control for constant level.
    I've not so far found an oscillator circuit in LTSpice with better harmonic distortion performance than this one.
    You can, of course, try to use filtering to reduce the unwanted harmonics. Removing the first four harmonics produced by this
    circuit will get it approaching 130dB but don't ask me how that would be measured in reality or what it would cost to do so even
    if
    it can be measured.

    Open LT Spice and make a 1 KHz sinewave voltage source. Run for 10
    seconds and FFT. The 3rd harmonic is down 48 dB.

    So Spicing low distortion oscillators might not be an exercize in
    reality.


    The following circuit was simulated in LTSpice 2.1.0 with all possible updates as of today.
    I stopped the simulation after two seconds worth of watching source, input and output.
    I then selected a sample of about 20ms near 2s.
    I then did an FFT using the current zoom extent with Blackman-Harris window on each trace in turn.
    The following results give the difference between 1kHz and 2kHz.
    source -240dB
    input -190dB
    output -120dB

    How far this has anything to do with reality I do not know.

    Version 4.1
    SHEET 1 2196 932
    WIRE 0 -416 0 -448
    WIRE 208 -288 48 -288
    WIRE 112 -208 112 -240
    WIRE 48 -192 48 -288
    WIRE 80 -192 48 -192
    WIRE 208 -176 208 -288
    WIRE 208 -176 144 -176
    WIRE 256 -176 208 -176
    WIRE 320 -176 256 -176
    WIRE 0 -160 0 -336
    WIRE 80 -160 0 -160
    WIRE -224 -144 -224 -240
    WIRE 0 -112 0 -160
    WIRE 0 -112 -64 -112
    WIRE 112 -112 112 -144
    WIRE 736 -112 672 -112
    WIRE 864 -112 816 -112
    WIRE 0 -80 0 -112
    WIRE -64 -64 -64 -112
    WIRE 752 16 752 0
    WIRE -224 32 -224 -64
    WIRE -64 32 -64 0
    WIRE 0 32 0 0
    WIRE 480 32 400 32
    WIRE 560 32 480 32
    WIRE 672 32 672 -112
    WIRE 672 32 640 32
    WIRE 720 32 672 32
    WIRE 864 48 864 -112
    WIRE 864 48 784 48
    WIRE 896 48 864 48
    WIRE 1024 48 976 48
    WIRE 1184 48 1088 48
    WIRE 1248 48 1184 48
    WIRE 400 64 400 32
    WIRE 688 64 672 64
    WIRE 720 64 688 64
    WIRE 752 96 752 80
    WIRE 1248 112 1248 48
    WIRE 400 176 400 128
    WIRE 480 176 400 176
    WIRE 512 176 480 176
    WIRE 1248 208 1248 192
    WIRE 400 240 400 176
    WIRE 400 400 400 320
    FLAG 752 0 V+
    FLAG 1248 208 0
    FLAG 1184 48 output
    FLAG -224 32 0
    FLAG 752 96 0
    FLAG -224 -240 V+
    FLAG 688 64 half
    FLAG 112 -112 0
    FLAG 112 -240 V+
    FLAG 256 -176 half
    FLAG 0 32 0
    FLAG 0 -448 V+
    FLAG -64 32 0
    FLAG 400 400 0
    FLAG 480 32 input
    FLAG 480 176 source
    SYMBOL voltage -224 -160 R0
    WINDOW 123 0 0 Left 0
    WINDOW 39 10 135 Left 2
    WINDOW 0 10 0 Left 2
    WINDOW 3 15 104 Left 2
    SYMATTR InstName V2
    SYMATTR Value 32
    SYMBOL res 992 32 R90
    WINDOW 0 -4 57 VBottom 2
    WINDOW 3 32 56 VTop 2
    SYMATTR InstName R7
    SYMATTR Value 600
    SYMBOL res 1264 208 R180
    WINDOW 0 47 75 Left 2
    WINDOW 3 36 40 Left 2
    SYMATTR InstName R8
    SYMATTR Value 600
    SYMBOL res -16 -320 M180
    WINDOW 0 40 70 Left 2
    WINDOW 3 37 41 Left 2
    SYMATTR InstName R5
    SYMATTR Value 100k
    SYMBOL res -16 16 M180
    WINDOW 0 40 70 Left 2
    WINDOW 3 38 43 Left 2
    SYMATTR InstName R10
    SYMATTR Value 100k
    SYMBOL OpAmps\\LT1058 112 -240 R0
    SYMATTR InstName U5
    SYMBOL OpAmps\\LT1678 752 48 R0
    SYMATTR InstName U4
    SYMBOL cap -80 -64 R0
    SYMATTR InstName C3
    SYMATTR Value 10n
    SYMBOL cap 1088 32 R90
    WINDOW 0 0 32 VBottom 2
    WINDOW 3 32 32 VTop 2
    SYMATTR InstName C4
    SYMATTR Value 10000n
    SYMBOL voltage 400 224 R0
    WINDOW 123 0 0 Left 0
    WINDOW 39 0 0 Left 0
    SYMATTR InstName V1
    SYMATTR Value SINE(0 4 1000)
    SYMBOL cap 416 128 R180
    WINDOW 0 24 56 Left 2
    WINDOW 3 24 8 Left 2
    SYMATTR InstName C1
    SYMATTR Value 10000n
    SYMBOL res 832 -128 R90
    WINDOW 0 0 56 VBottom 2
    WINDOW 3 32 56 VTop 2
    SYMATTR InstName R2
    SYMATTR Value 10k
    SYMBOL res 544 48 R270
    WINDOW 0 32 56 VTop 2
    WINDOW 3 0 56 VBottom 2
    SYMATTR InstName R3
    SYMATTR Value 10k
    TEXT -304 200 Left 2 !.tran 0 30 0 1u uic
    TEXT -304 152 Left 2 !.options plotwinsize=0 numdgt=7 method=trap
    TEXT -272 -568 Left 2 ;1kHz low distortion sinewave generator.
    TEXT -272 -536 Left 2 ;24 Jan 2025.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Bill Sloman@21:1/5 to Edward Rawde on Wed Jan 29 18:06:01 2025
    On 24/01/2025 5:02 pm, Edward Rawde wrote:
    "Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vmv6ac$22ufe$1@dont-email.me...
    On 24/01/2025 11:14 am, Edward Rawde wrote:
    Before you can make a 1kHz sinewave oscillator with constant output level and better than 120dB harmonic distortion you'll need
    an
    oscillator which does better than that when it passes through the required output level.

    This is obviously true. Why do you think you need to tell us about it?


    You do make me laugh sometimes Bill.
    Your circuit doesn't come anywhere close to 120dB but it does depend on which simulator you ask.

    I never said it did. I was looking for comments on the way the current
    mirrors might screw up the waveform. I didn't get any.

    Adding a FET gain stabilizer to the circuit I posted seems to have negligible effect on the distortion.

    Then you haven't looked at the current waveform going through the the FET.

    So I'd concentrate on the oscillator distortion level rather than the gain controller contribution if I wanted to attempt better
    than 120dB.

    And you'd probably better dump LTSpice 24.1 - it has been claimed that
    it has a serious bug. That might explain why your simulations of my
    circuit run a thousand times slower for you than they do for me and a
    couple of other people.

    --
    Bill Sloman, Sydney

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Edward Rawde@21:1/5 to Bill Sloman on Wed Jan 29 10:31:29 2025
    "Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vnck1i$295d5$1@dont-email.me...
    On 24/01/2025 5:02 pm, Edward Rawde wrote:
    "Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vmv6ac$22ufe$1@dont-email.me...
    On 24/01/2025 11:14 am, Edward Rawde wrote:
    Before you can make a 1kHz sinewave oscillator with constant output level and better than 120dB harmonic distortion you'll need
    an
    oscillator which does better than that when it passes through the required output level.

    This is obviously true. Why do you think you need to tell us about it?


    You do make me laugh sometimes Bill.
    Your circuit doesn't come anywhere close to 120dB but it does depend on which simulator you ask.

    I never said it did.

    I never said you said it did.
    Facts are still facts whether anyone says them or not.

    I was looking for comments on the way the current mirrors might screw up the waveform. I didn't get any.

    Adding a FET gain stabilizer to the circuit I posted seems to have negligible effect on the distortion.

    Then you haven't looked at the current waveform going through the the FET.

    But I have looked at the distortion level both with and without the FET stabilizer and I have not found any difference worth having
    in an LTSpice simulation.
    In any case the current going through the FET also goes through the parallel resistor which, as you pointed out some time ago,
    should be as small as possible.

    Perhaps JL would like to elaborate on what he means by two FETs in anti-parallel. How would you drive the gate of the other FET?


    So I'd concentrate on the oscillator distortion level rather than the gain controller contribution if I wanted to attempt better
    than 120dB.

    And you'd probably better dump LTSpice 24.1 - it has been claimed that it has a serious bug.

    Could you please provide a reference to this claim.
    Who has claimed that it has a serious bug and is there an online discussion anywhere?
    Exactly what is this serious bug other than the fact that your circuit gets completely different results?

    That might explain why your simulations of my circuit run a thousand times slower for you than they do for me and a couple of
    other people.

    There is obviously a big difference but I have not so far seen any evidence to confirm that it is a serious bug.


    --
    Bill Sloman, Sydney


    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Edward Rawde@21:1/5 to Bill Sloman on Wed Jan 29 14:13:33 2025
    "Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vnck1i$295d5$1@dont-email.me...
    On 24/01/2025 5:02 pm, Edward Rawde wrote:
    "Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vmv6ac$22ufe$1@dont-email.me...
    On 24/01/2025 11:14 am, Edward Rawde wrote:
    Before you can make a 1kHz sinewave oscillator with constant output level and better than 120dB harmonic distortion you'll need
    an
    oscillator which does better than that when it passes through the required output level.

    This is obviously true. Why do you think you need to tell us about it?


    You do make me laugh sometimes Bill.
    Your circuit doesn't come anywhere close to 120dB but it does depend on which simulator you ask.

    I never said it did. I was looking for comments on the way the current mirrors might screw up the waveform. I didn't get any.

    Adding a FET gain stabilizer to the circuit I posted seems to have negligible effect on the distortion.

    Then you haven't looked at the current waveform going through the the FET.

    So I'd concentrate on the oscillator distortion level rather than the gain controller contribution if I wanted to attempt better
    than 120dB.

    And you'd probably better dump LTSpice 24.1 - it has been claimed that it has a serious bug. That might explain why your
    simulations of my circuit run a thousand times slower for you than they do for me and a couple of other people.

    24.1.1 is now available. Simulation speed of your circuit is still 25us/s. Parasitic 22.6MHz at about 20mV pk-pk is still present.


    --
    Bill Sloman, Sydney


    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Edward Rawde@21:1/5 to Bill Sloman on Wed Jan 29 15:35:17 2025
    "Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vnck1i$295d5$1@dont-email.me...
    On 24/01/2025 5:02 pm, Edward Rawde wrote:
    "Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vmv6ac$22ufe$1@dont-email.me...
    On 24/01/2025 11:14 am, Edward Rawde wrote:
    Before you can make a 1kHz sinewave oscillator with constant output level and better than 120dB harmonic distortion you'll need
    an
    oscillator which does better than that when it passes through the required output level.

    This is obviously true. Why do you think you need to tell us about it?


    You do make me laugh sometimes Bill.
    Your circuit doesn't come anywhere close to 120dB but it does depend on which simulator you ask.

    I never said it did. I was looking for comments on the way the current mirrors might screw up the waveform. I didn't get any.

    Adding a FET gain stabilizer to the circuit I posted seems to have negligible effect on the distortion.

    Then you haven't looked at the current waveform going through the the FET.

    So I'd concentrate on the oscillator distortion level rather than the gain controller contribution if I wanted to attempt better
    than 120dB.

    And you'd probably better dump LTSpice 24.1 - it has been claimed that it has a serious bug. That might explain why your
    simulations of my circuit run a thousand times slower for you than they do for me and a couple of other people.

    LTSpice 24.1.1 is now available.
    The circuit below produces a 24mV pk-pk sineish wave at 23 MHz on my installation of LTSpice 24.1.1 with all component updates.
    FFT shows 23 MHz at -40dB
    Simulation speed is about 115 us/s
    I didn't simulate beyond 2.5 ms

    Simulation in LTSpice 24.0.12 shows pretty much identical behaviour but the simulation speed is slower at about 75us/s.

    Version 4.1
    SHEET 1 3608 920
    WIRE -1104 -2032 -1136 -2032
    WIRE -1088 -2032 -1104 -2032
    WIRE -1136 -1968 -1136 -2032
    WIRE -1136 -1968 -1232 -1968
    WIRE -1232 -1952 -1232 -1968
    WIRE -1136 -1904 -1136 -1968
    WIRE 336 -1888 336 -1904
    WIRE -576 -1840 -912 -1840
    WIRE -32 -1840 -496 -1840
    WIRE -1232 -1808 -1232 -1888
    WIRE -1232 -1808 -1296 -1808
    WIRE -1136 -1808 -1136 -1824
    WIRE -1136 -1808 -1232 -1808
    WIRE -1296 -1792 -1296 -1808
    WIRE -1136 -1760 -1136 -1808
    WIRE -1232 -1744 -1232 -1808
    WIRE -912 -1712 -912 -1840
    WIRE -864 -1712 -912 -1712
    WIRE -720 -1712 -784 -1712
    WIRE -544 -1712 -640 -1712
    WIRE -128 -1712 -272 -1712
    WIRE -32 -1712 -32 -1840
    WIRE -32 -1712 -64 -1712
    WIRE -1232 -1632 -1232 -1680
    WIRE -1136 -1632 -1136 -1680
    WIRE -1136 -1632 -1232 -1632
    WIRE -272 -1616 -272 -1712
    WIRE -144 -1616 -272 -1616
    WIRE -32 -1616 -32 -1712
    WIRE -32 -1616 -64 -1616
    WIRE -544 -1584 -544 -1712
    WIRE -512 -1584 -544 -1584
    WIRE -432 -1584 -448 -1584
    WIRE -272 -1584 -272 -1616
    WIRE -272 -1584 -352 -1584
    WIRE -208 -1584 -224 -1584
    WIRE -176 -1584 -208 -1584
    WIRE -176 -1552 -176 -1584
    WIRE -272 -1536 -272 -1584
    WIRE -208 -1536 -272 -1536
    WIRE -32 -1520 -32 -1616
    WIRE -32 -1520 -144 -1520
    WIRE 16 -1520 -32 -1520
    WIRE 112 -1520 16 -1520
    WIRE -1136 -1504 -1136 -1632
    WIRE -1088 -1504 -1136 -1504
    WIRE -1056 -1504 -1088 -1504
    WIRE -208 -1504 -288 -1504
    WIRE -624 -1472 -656 -1472
    WIRE -608 -1472 -624 -1472
    WIRE -288 -1456 -288 -1504
    WIRE -656 -1440 -656 -1472
    WIRE -224 -1440 -256 -1440
    WIRE -176 -1440 -176 -1488
    WIRE -176 -1440 -224 -1440
    WIRE -912 -1424 -912 -1712
    WIRE -688 -1424 -912 -1424
    WIRE -544 -1408 -544 -1584
    WIRE -544 -1408 -624 -1408
    WIRE -688 -1392 -704 -1392
    WIRE -704 -1328 -704 -1392
    WIRE -656 -1328 -656 -1376
    WIRE -608 -1328 -656 -1328
    WIRE -576 -1328 -608 -1328
    FLAG -1296 -1792 0
    FLAG -1104 -2032 Vcc
    FLAG -704 -1328 0
    FLAG 16 -1520 Vout
    FLAG -1088 -1504 Vee
    FLAG -288 -1456 0
    FLAG -624 -1472 Vcc
    FLAG -208 -1584 Vcc
    FLAG -608 -1328 Vee
    FLAG -224 -1440 Vee
    SYMBOL voltage -1136 -1920 R0
    WINDOW 123 0 0 Left 0
    WINDOW 39 0 0 Left 0
    SYMATTR InstName V1
    SYMATTR Value 12
    SYMBOL voltage -1136 -1776 R0
    WINDOW 123 0 0 Left 0
    WINDOW 39 0 0 Left 0
    SYMATTR InstName V2
    SYMATTR Value 12
    SYMBOL cap -448 -1600 R90
    WINDOW 0 0 32 VBottom 2
    WINDOW 3 32 32 VTop 2
    SYMATTR InstName C5
    SYMATTR Value 15n
    SYMATTR SpiceLine V=63 Rser=4 Lser=12n
    SYMBOL res -448 -1568 R270
    WINDOW 0 27 56 VTop 2
    WINDOW 3 5 56 VBottom 2
    SYMATTR InstName R4
    SYMATTR Value 10.7k
    SYMATTR SpiceLine tol=1
    SYMBOL cap -64 -1728 R90
    WINDOW 0 0 32 VBottom 2
    WINDOW 3 32 32 VTop 2
    SYMATTR InstName C6
    SYMATTR Value 15n
    SYMATTR SpiceLine V=63 Rser=4 Lser=12n
    SYMBOL res -480 -1856 R90
    WINDOW 0 0 56 VBottom 2
    WINDOW 3 32 56 VTop 2
    SYMATTR InstName R22
    SYMATTR Value 2.49k
    SYMATTR SpiceLine tol=1
    SYMBOL cap -1248 -1952 R0
    WINDOW 0 -60 15 Left 2
    WINDOW 3 -62 54 Left 2
    SYMATTR InstName C7
    SYMATTR Value 100n
    SYMBOL cap -1248 -1744 R0
    WINDOW 0 -60 15 Left 2
    WINDOW 3 -62 54 Left 2
    SYMATTR InstName C23
    SYMATTR Value 100n
    SYMBOL res -160 -1600 R270
    WINDOW 0 27 56 VTop 2
    WINDOW 3 5 56 VBottom 2
    SYMATTR InstName R26
    SYMATTR Value 10.7k
    SYMATTR SpiceLine tol=1
    SYMBOL res -768 -1728 R90
    WINDOW 0 0 56 VBottom 2
    WINDOW 3 32 56 VTop 2
    SYMATTR InstName R5
    SYMATTR Value 4.99k
    SYMATTR SpiceLine tol=1
    SYMBOL Opamps\\LT1115 -656 -1472 R0
    SYMATTR InstName U3
    SYMBOL Opamps\\LT1115 -176 -1584 R0
    SYMATTR InstName U8
    SYMBOL res -624 -1728 R90
    WINDOW 0 0 56 VBottom 2
    WINDOW 3 32 56 VTop 2
    SYMATTR InstName R20
    SYMATTR Value 120
    TEXT -1248 -1352 Left 2 !.tran 0 10s 0s startup

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Edward Rawde@21:1/5 to Bill Sloman on Wed Jan 29 18:25:29 2025
    "Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vnck1i$295d5$1@dont-email.me...
    On 24/01/2025 5:02 pm, Edward Rawde wrote:
    "Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vmv6ac$22ufe$1@dont-email.me...
    On 24/01/2025 11:14 am, Edward Rawde wrote:
    Before you can make a 1kHz sinewave oscillator with constant output level and better than 120dB harmonic distortion you'll need
    an
    oscillator which does better than that when it passes through the required output level.

    This is obviously true. Why do you think you need to tell us about it?


    You do make me laugh sometimes Bill.
    Your circuit doesn't come anywhere close to 120dB but it does depend on which simulator you ask.

    I never said it did. I was looking for comments on the way the current mirrors might screw up the waveform. I didn't get any.

    Adding a FET gain stabilizer to the circuit I posted seems to have negligible effect on the distortion.

    Then you haven't looked at the current waveform going through the the FET.

    So I'd concentrate on the oscillator distortion level rather than the gain controller contribution if I wanted to attempt better
    than 120dB.

    And you'd probably better dump LTSpice 24.1 - it has been claimed that it has a serious bug. That might explain why your
    simulations of my circuit run a thousand times slower for you than they do for me and a couple of other people.

    If U3 and U8 (LT1115) in your circuit are replaced with LT1678 then on my computer with LTSpice 24.1.1 and all component updates,
    the simulation completes almost as fast as I can start it, at about 55 ms/s.
    A sample near 10s is not quite 60dB down at 3kHz and 5kHz and 70dB down at 7kHz, approaching 80dB down everywhere else.
    The parasitic 23MHz signal has gone.

    So the reason for the slow simulation speed in 24.1.1 is something to do with LT1115.

    The circuit I simulated in 24.1.1 with LT1678 is below.

    Version 4.1
    SHEET 1 3608 920
    WIRE -1680 -2400 -1984 -2400
    WIRE -1360 -2400 -1680 -2400
    WIRE -1200 -2400 -1360 -2400
    WIRE -1104 -2400 -1200 -2400
    WIRE -736 -2400 -1104 -2400
    WIRE -320 -2400 -736 -2400
    WIRE 208 -2400 -320 -2400
    WIRE 336 -2400 208 -2400
    WIRE 576 -2400 336 -2400
    WIRE -736 -2384 -736 -2400
    WIRE 208 -2384 208 -2400
    WIRE -320 -2368 -320 -2400
    WIRE 3376 -2272 -1616 -2272
    WIRE 880 -2192 -1776 -2192
    WIRE -1360 -2160 -1360 -2400
    WIRE -736 -2160 -736 -2320
    WIRE -656 -2160 -736 -2160
    WIRE -320 -2160 -320 -2304
    WIRE -176 -2160 -320 -2160
    WIRE 208 -2144 208 -2320
    WIRE 336 -2144 208 -2144
    WIRE -1200 -2112 -1200 -2400
    WIRE -1680 -2096 -1680 -2400
    WIRE -1360 -2048 -1360 -2080
    WIRE -320 -2000 -320 -2160
    WIRE -736 -1984 -736 -2160
    WIRE -1776 -1968 -1776 -2192
    WIRE 336 -1968 336 -2144
    WIRE 576 -1968 576 -2400
    WIRE -1360 -1920 -1360 -1968
    WIRE -1200 -1920 -1200 -2032
    WIRE 1952 -1920 1744 -1920
    WIRE 2160 -1920 1952 -1920
    WIRE -1616 -1904 -1616 -2272
    WIRE 1376 -1904 1072 -1904
    WIRE 1536 -1904 1376 -1904
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    WIRE 2432 -1712 2432 -1776
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    WIRE -2016 -1696 -2064 -1696
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    WIRE -1072 -1616 -1200 -1616
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    WIRE -32 -1616 -64 -1616
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    WIRE 1392 -1600 1392 -1648
    WIRE 1904 -1600 1904 -1824
    WIRE 2032 -1600 1904 -1600
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    WIRE -544 -1584 -544 -1632
    WIRE -512 -1584 -544 -1584
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    WIRE -32 -1520 -144 -1520
    WIRE 16 -1520 -32 -1520
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    WIRE 1232 -1440 1232 -1584
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    WIRE 496 -1392 496 -1456
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    WIRE 1904 -1392 1904 -1600
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    WIRE 3152 -1392 3088 -1392
    WIRE -1680 -1376 -1680 -2016
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    WIRE 144 -1360 144 -1456
    WIRE 256 -1360 144 -1360
    WIRE 368 -1360 368 -1456
    WIRE 368 -1360 320 -1360
    WIRE -992 -1344 -992 -1376
    WIRE -432 -1344 -992 -1344
    WIRE 64 -1344 64 -1520
    WIRE 64 -1344 -352 -1344
    WIRE 2000 -1344 2000 -1568
    WIRE -1680 -1328 -1680 -1376
    WIRE 64 -1328 64 -1344
    WIRE 368 -1312 368 -1360
    WIRE 3152 -1312 3152 -1392
    WIRE -1520 -1296 -1520 -1328
    WIRE -1440 -1296 -1520 -1296
    WIRE -1360 -1296 -1360 -1328
    WIRE -1360 -1296 -1440 -1296
    WIRE -992 -1280 -992 -1344
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    WIRE 576 -1232 576 -1776
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    WIRE -320 -1216 -560 -1216
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    WIRE 880 -1200 608 -1200
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    FLAG 336 -2400 Vcc
    FLAG 416 -624 Vee
    FLAG -560 -1152 0
    FLAG 16 -1520 Vout
    FLAG 2576 -960 0
    FLAG 2432 -1456 Vcc
    FLAG -1040 -704 Vee
    FLAG -288 -1456 0
    FLAG 336 -1888 0
    FLAG 1376 -1904 filt1
    FLAG 1648 -1648 Vcc
    FLAG 1632 -1456 Vee
    FLAG 1520 -1152 0
    FLAG 1952 -1920 filter2
    FLAG 2432 -1584 0
    FLAG -2064 -1584 0
    SYMBOL Opamps\\LT1360 208 -1184 R0
    SYMATTR InstName U1
    SYMBOL res 48 -1344 R0
    WINDOW 0 41 37 Left 2
    WINDOW 3 36 71 Left 2
    SYMATTR InstName R1
    SYMATTR Value 10k
    SYMATTR SpiceLine tol=0.1
    SYMBOL res -64 -1152 R0
    WINDOW 3 41 74 Left 2
    WINDOW 0 43 31 Left 2
    SYMATTR Value 4k02
    SYMATTR InstName R2
    SYMATTR SpiceLine tol=1
    SYMBOL cap -160 -1136 R0
    SYMATTR InstName C1
    SYMATTR Value 3.3n
    SYMBOL schottky 352 -1312 R0
    WINDOW 3 -89 62 Left 2
    WINDOW 0 -92 37 Left 2
    SYMATTR Value BAS70L
    SYMATTR InstName D1
    SYMBOL schottky 352 -1088 R0
    WINDOW 3 -78 61 Left 2
    WINDOW 0 -81 40 Left 2
    SYMATTR Value BAS70L
    SYMATTR InstName D2
    SYMBOL res 352 -1472 R90
    WINDOW 0 0 56 VBottom 2
    WINDOW 3 32 56 VTop 2
    SYMATTR InstName R1a
    SYMATTR Value 10k
    SYMATTR SpiceLine tol=0.1
    SYMBOL res 208 -1536 R90
    WINDOW 0 0 56 VBottom 2
    WINDOW 3 32 56 VTop 2
    SYMATTR InstName R3
    SYMATTR Value 20k
    SYMATTR SpiceLine tol=1
    SYMBOL res 480 -1408 R0
    WINDOW 0 41 41 Left 2
    WINDOW 3 34 79 Left 2
    SYMATTR InstName R2a
    SYMATTR Value 10k
    SYMATTR SpiceLine tol=0.1
    SYMBOL res 560 -928 R90
    WINDOW 0 0 56 VBottom 2
    WINDOW 3 32 56 VTop 2
    SYMATTR InstName R2b
    SYMATTR Value 10k
    SYMATTR SpiceLine tol=0.1
    SYMBOL res 720 -928 R90
    WINDOW 0 0 56 VBottom 2
    WINDOW 3 32 56 VTop 2
    SYMATTR InstName R2c
    SYMATTR Value 10k
    SYMATTR SpiceLine tol=0.1
    SYMBOL cap 160 -960 R90
    WINDOW 0 0 32 VBottom 2
    WINDOW 3 32 32 VTop 2
    SYMATTR InstName C4
    SYMATTR Value 3.3p
    SYMBOL res 48 -896 R0
    WINDOW 0 39 33 Left 2
    WINDOW 3 40 74 Left 2
    SYMATTR InstName R1b
    SYMATTR Value 10k
    SYMATTR SpiceLine tol=0.1
    SYMBOL voltage -1104 -1120 R0
    WINDOW 123 0 0 Left 0
    WINDOW 39 0 0 Left 0
    SYMATTR InstName V1
    SYMATTR Value 12
    SYMBOL voltage -1104 -976 R0
    WINDOW 123 0 0 Left 0
    WINDOW 39 0 0 Left 0
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    SYMBOL cap -448 -1600 R90
    WINDOW 0 0 32 VBottom 2
    WINDOW 3 32 32 VTop 2
    SYMATTR InstName C5
    SYMATTR Value 15n
    SYMATTR SpiceLine V=63 Rser=4 Lser=12n
    SYMBOL res -448 -1568 R270
    WINDOW 0 27 56 VTop 2
    WINDOW 3 5 56 VBottom 2
    SYMATTR InstName R4
    SYMATTR Value 10.7k
    SYMATTR SpiceLine tol=1
    SYMBOL cap -64 -1728 R90
    WINDOW 0 0 32 VBottom 2
    WINDOW 3 32 32 VTop 2
    SYMATTR InstName C6
    SYMATTR Value 15n
    SYMATTR SpiceLine V=63 Rser=4 Lser=12n
    SYMBOL cap 3104 -1664 R180
    WINDOW 0 24 64 Left 2
    WINDOW 3 24 8 Left 2
    SYMATTR InstName C8
    SYMATTR Value 22n
    SYMBOL res 2848 -1760 R270
    WINDOW 0 32 56 VTop 2
    WINDOW 3 0 56 VBottom 2
    SYMATTR InstName R10
    SYMATTR Value 220k
    SYMBOL Opamps\\LT1056A 2992 -1456 R0
    SYMATTR InstName U5
    SYMBOL cap 2784 -1120 R0
    SYMATTR InstName C10
    SYMATTR Value 3300n
    SYMBOL cap 2912 -1552 R90
    WINDOW 0 0 32 VBottom 2
    WINDOW 3 32 32 VTop 2
    SYMATTR InstName C11
    SYMATTR Value 3.3p
    SYMBOL Opamps\\OP27 576 -1264 R0
    SYMATTR InstName U2
    SYMBOL FerriteBead 576 -672 R0
    SYMATTR InstName L2
    SYMATTR Value 1000n
    SYMATTR SpiceLine Ipk=0.2 Rser=0.562 Rpar=750 Cpar=350f mfg="Würth Elektronik" pn="782422601 WE-CBA 0402"
    SYMBOL cap 752 -1408 R0
    SYMATTR InstName C15
    SYMATTR Value 100n
    SYMBOL cap 752 -800 R0
    SYMATTR InstName C16
    SYMATTR Value 100n
    SYMBOL FerriteBead -176 -928 R0
    SYMATTR InstName L4
    SYMATTR Value 1000n
    SYMATTR SpiceLine Ipk=0.2 Rser=0.562 Rpar=750 Cpar=350f mfg="Würth Elektronik" pn="782422601 WE-CBA 0402"
    SYMBOL cap -336 -2000 R0
    WINDOW 0 -60 15 Left 2
    WINDOW 3 -62 54 Left 2
    SYMATTR InstName C17
    SYMATTR Value 100n
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    WINDOW 0 -60 15 Left 2
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    SYMATTR Value 100n
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    SYMATTR InstName C21
    SYMATTR Value 100n
    SYMBOL FerriteBead 2288 -1408 R0
    SYMATTR InstName L7
    SYMATTR Value 1000n
    SYMATTR SpiceLine Ipk=0.2 Rser=0.562 Rpar=750 Cpar=350f mfg="Würth Elektronik" pn="782422601 WE-CBA 0402"
    SYMBOL res -480 -1888 R90
    WINDOW 0 0 56 VBottom 2
    WINDOW 3 32 56 VTop 2
    SYMATTR InstName R22
    SYMATTR Value 2.49k
    SYMATTR SpiceLine tol=1
    SYMBOL FerriteBead -320 -2336 R0
    SYMATTR InstName L8
    SYMATTR Value 1000n
    SYMATTR SpiceLine Ipk=0.2 Rser=0.562 Rpar=750 Cpar=350f mfg="Würth Elektronik" pn="782422601 WE-CBA 0402"
    SYMBOL cap -752 -1984 R0
    WINDOW 0 -60 15 Left 2
    WINDOW 3 -62 54 Left 2
    SYMATTR InstName C7
    SYMATTR Value 100n
    SYMBOL FerriteBead -736 -2352 R0
    SYMATTR InstName L3
    SYMATTR Value 1000n
    SYMATTR SpiceLine Ipk=0.2 Rser=0.562 Rpar=750 Cpar=350f mfg="Würth Elektronik" pn="782422601 WE-CBA 0402"
    SYMBOL FerriteBead -656 -896 R0
    SYMATTR InstName L9
    SYMATTR Value 1000n
    SYMATTR SpiceLine Ipk=0.2 Rser=0.562 Rpar=750 Cpar=350f mfg="Würth Elektronik" pn="782422601 WE-CBA 0402"
    SYMBOL cap -864 -1152 R0
    WINDOW 0 -60 15 Left 2
    WINDOW 3 -62 54 Left 2
    SYMATTR InstName C23
    SYMATTR Value 100n
    SYMBOL res -160 -1600 R270
    WINDOW 0 27 56 VTop 2
    WINDOW 3 5 56 VBottom 2
    SYMATTR InstName R26
    SYMATTR Value 10.7k
    SYMATTR SpiceLine tol=1
    SYMBOL res -768 -1808 R90
    WINDOW 0 0 56 VBottom 2
    WINDOW 3 32 56 VTop 2
    SYMATTR InstName R5
    SYMATTR Value 4.99k
    SYMATTR SpiceLine tol=1
    SYMBOL cap -784 -1648 R90
    WINDOW 0 0 32 VBottom 2
    WINDOW 3 32 32 VTop 2
    SYMATTR InstName C19
    SYMATTR Value 10p
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    SYMATTR InstName L5
    SYMATTR Value 1000n
    SYMATTR SpiceLine Ipk=0.2 Rser=0.562 Rpar=750 Cpar=350f mfg="Würth Elektronik" pn="782422601 WE-CBA 0402"
    SYMBOL FerriteBead 208 -2352 R0
    SYMATTR InstName L6
    SYMATTR Value 1000n
    SYMATTR SpiceLine Ipk=0.2 Rser=0.562 Rpar=750 Cpar=350f mfg="Würth Elektronik" pn="782422601 WE-CBA 0402"
    SYMBOL cap 320 -1968 R0
    WINDOW 0 -60 15 Left 2
    WINDOW 3 -62 54 Left 2
    SYMATTR InstName C20
    SYMATTR Value 100n
    SYMBOL cap -96 -816 R0
    WINDOW 0 -60 15 Left 2
    WINDOW 3 -62 54 Left 2
    SYMATTR InstName C22
    SYMATTR Value 100n
    SYMBOL References\\LTC6655-1.25 2560 -1120 R0
    SYMATTR InstName U4
    SYMBOL cap -64 -1824 R90
    WINDOW 0 0 32 VBottom 2
    WINDOW 3 32 32 VTop 2
    SYMATTR InstName C9
    SYMATTR Value 10p
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    SYMATTR InstName L13
    SYMATTR Value 1000n
    SYMATTR SpiceLine Ipk=0.2 Rser=0.562 Rpar=750 Cpar=350f mfg="Würth Elektronik" pn="782422601 WE-CBA 0402"
    SYMBOL cap 704 -1088 R90
    WINDOW 0 0 32 VBottom 2
    WINDOW 3 32 32 VTop 2
    SYMATTR InstName C13
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    WINDOW 0 0 56 VBottom 2
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    WINDOW 0 0 56 VBottom 2
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    SYMBOL res 1216 -1456 R0
    SYMATTR InstName R13
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    SYMBOL cap 1312 -1392 R0
    SYMATTR InstName C3
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    WINDOW 0 0 56 VBottom 2
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    SYMATTR InstName R14
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    SYMBOL res 896 -1536 R270
    WINDOW 0 32 56 VTop 2
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    SYMATTR Value 18.7k
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    WINDOW 0 0 56 VBottom 2
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    SYMATTR InstName R16
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    SYMBOL cap 1728 -1872 R0
    SYMATTR InstName C14
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    WINDOW 0 0 56 VBottom 2
    WINDOW 3 32 56 VTop 2
    SYMATTR InstName R17
    SYMATTR Value 14k
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    SYMATTR InstName U7
    SYMBOL res 1568 -1552 R270
    WINDOW 0 32 56 VTop 2
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    SYMATTR Value 18.7k
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    SYMATTR InstName R19
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    SYMBOL cap 1984 -1344 R0
    SYMATTR InstName C24
    SYMATTR Value 18n
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    SYMATTR InstName Q1
    SYMATTR Value 2N5089
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    SYMATTR InstName Q2
    SYMATTR Value 2N5089
    SYMBOL res 2384 -1792 R90
    WINDOW 0 0 56 VBottom 2
    WINDOW 3 32 56 VTop 2
    SYMATTR InstName R9
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    WINDOW 0 0 32 VBottom 2
    WINDOW 3 32 32 VTop 2
    SYMATTR InstName C2
    SYMATTR Value 3.3p
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    SYMATTR Value 68
    SYMBOL pnp -1840 -1632 M180
    WINDOW 3 84 0 Left 2
    SYMATTR Value 2N5087
    SYMATTR InstName Q3
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    SYMATTR InstName R11
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    SYMATTR Value 47k
    SYMBOL pnp -1296 -1824 R180
    WINDOW 3 84 0 Left 2
    SYMATTR Value 2N5087
    SYMATTR InstName Q7
    SYMBOL pnp -1264 -1824 M180
    WINDOW 0 57 29 Left 2
    WINDOW 3 60 62 Left 2
    SYMATTR InstName Q8
    SYMATTR Value 2N5087
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    WINDOW 0 27 56 VTop 2
    WINDOW 3 5 56 VBottom 2
    SYMATTR InstName R23
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    SYMATTR SpiceLine tol=1
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    SYMATTR Value 1.5k
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    SYMATTR InstName R24
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    WINDOW 0 57 29 Left 2
    WINDOW 3 60 62 Left 2
    SYMATTR InstName Q9
    SYMATTR Value 2N5087
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    SYMATTR InstName Q10
    SYMATTR Value 2N5089
    SYMBOL res -1376 -2064 R0
    SYMATTR InstName R27
    SYMATTR Value 6.2
    SYMBOL Opamps\\LT1013 -1984 -1744 R0
    SYMATTR InstName U9
    SYMBOL res -560 -1744 R0
    SYMATTR InstName R20
    SYMATTR Value 120
    SYMBOL Opamps\\LT1056A 3264 -1088 R0
    SYMATTR InstName U10
    SYMBOL res 3136 -1328 R0
    SYMATTR InstName R25
    SYMATTR Value 10k
    SYMBOL res 3136 -944 R0
    SYMATTR InstName R29
    SYMATTR Value 10k
    SYMBOL res -976 -1632 R90
    WINDOW 0 0 56 VBottom 2
    WINDOW 3 32 56 VTop 2
    SYMATTR InstName R30
    SYMATTR Value 1
    SYMATTR SpiceLine tol=1
    SYMBOL res -1008 -1296 R0
    SYMATTR InstName R31
    SYMATTR Value 20k
    SYMBOL res -1696 -2112 R0
    SYMATTR InstName R32
    SYMATTR Value 36k
    SYMATTR SpiceLine tol=1
    SYMBOL res -1696 -1344 R0
    SYMATTR InstName R33
    SYMATTR Value 18k
    SYMBOL npn -1584 -1424 R0
    SYMATTR InstName Q5
    SYMATTR Value 2N5089
    SYMBOL npn -1296 -1424 M0
    SYMATTR InstName Q6
    SYMATTR Value 2N5089
    SYMBOL OpAmps\\LT1678 -656 -1408 R0
    SYMATTR InstName U3
    SYMBOL OpAmps\\LT1678 -176 -1520 R0
    SYMATTR InstName U8
    TEXT -1736 -600 Left 2 !.MODEL BAS70L D IS = 3.22E-9 N = 1.018 BV = 77 IBV = 1.67E-7 RS = 20.89 CJO = 1.608E-12 VJ = 0.3891 M =
    0.3683 FC = 0.5 EG = 0.69 XTI = 2
    TEXT -336 -528 Left 2 ;R2 a,b,c, Vishay Beschlag ACAS06S0830372P1AT precision 10k resistor \n at R1a, R1b Maxim MAX5492LB10000+T
    10K resistive divider in a SOT-23-5 package
    TEXT -1136 -536 Left 2 !.tran 0 10s 0s startup

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Bill Sloman@21:1/5 to Edward Rawde on Thu Jan 30 16:02:53 2025
    On 30/01/2025 10:25 am, Edward Rawde wrote:
    "Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vnck1i$295d5$1@dont-email.me...
    On 24/01/2025 5:02 pm, Edward Rawde wrote:
    "Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vmv6ac$22ufe$1@dont-email.me...
    On 24/01/2025 11:14 am, Edward Rawde wrote:
    Before you can make a 1kHz sinewave oscillator with constant output level and better than 120dB harmonic distortion you'll need
    an
    oscillator which does better than that when it passes through the required output level.

    This is obviously true. Why do you think you need to tell us about it? >>>>

    You do make me laugh sometimes Bill.
    Your circuit doesn't come anywhere close to 120dB but it does depend on which simulator you ask.

    I never said it did. I was looking for comments on the way the current mirrors might screw up the waveform. I didn't get any.

    Adding a FET gain stabilizer to the circuit I posted seems to have negligible effect on the distortion.

    Then you haven't looked at the current waveform going through the the FET. >>
    So I'd concentrate on the oscillator distortion level rather than the gain controller contribution if I wanted to attempt better
    than 120dB.

    And you'd probably better dump LTSpice 24.1 - it has been claimed that it has a serious bug. That might explain why your
    simulations of my circuit run a thousand times slower for you than they do for me and a couple of other people.

    If U3 and U8 (LT1115) in your circuit are replaced with LT1678 then on my computer with LTSpice 24.1.1 and all component updates,
    the simulation completes almost as fast as I can start it, at about 55 ms/s. A sample near 10s is not quite 60dB down at 3kHz and 5kHz and 70dB down at 7kHz, approaching 80dB down everywhere else.
    The parasitic 23MHz signal has gone.

    The LT1678 looks like a nice part, but at $10 each it has to be. The application doesn't need a rail-to-rail op amp.

    John May has pointed out to me that the LT1115 LTSpice model is just a
    variant of the LT1028 Spice model. I used the LT1028 in a rather
    demanding application some forty years ago and while it had its
    idiosyncracies, generating a 23MHz parasitic oscillation wasn't one of them.

    The performance you are now getting sounds like what I've been seeing
    all along, and presumably reflects the defects of the current mirrors.

    I've tried to improve them a bit but never got more than a dB or two of improvement. I need better insight. Talking to people often helps
    develop that but it hasn't worked here.

    --
    Bill Sloman, Sydney

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Bill Sloman@21:1/5 to Edward Rawde on Thu Jan 30 15:45:04 2025
    On 30/01/2025 2:31 am, Edward Rawde wrote:
    "Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vnck1i$295d5$1@dont-email.me...
    On 24/01/2025 5:02 pm, Edward Rawde wrote:
    "Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vmv6ac$22ufe$1@dont-email.me...
    On 24/01/2025 11:14 am, Edward Rawde wrote:
    Before you can make a 1kHz sinewave oscillator with constant output level and better than 120dB harmonic distortion you'll need
    an
    oscillator which does better than that when it passes through the required output level.

    This is obviously true. Why do you think you need to tell us about it? >>>>

    You do make me laugh sometimes Bill.
    Your circuit doesn't come anywhere close to 120dB but it does depend on which simulator you ask.

    I never said it did.

    I never said you said it did.
    Facts are still facts whether anyone says them or not.

    But your line does imply that I did, and that is a fact.

    I was looking for comments on the way the current mirrors might screw up the waveform. I didn't get any.

    Adding a FET gain stabilizer to the circuit I posted seems to have negligible effect on the distortion.

    Then you haven't looked at the current waveform going through the the FET.

    But I have looked at the distortion level both with and without the FET stabilizer and I have not found any difference worth having
    in an LTSpice simulation.

    Then you haven't looked hard enough. Get LTSpice to plot the current
    through the FET minus the sine function current that ought to be running through it.

    In any case the current going through the FET also goes through the
    parallel resistor which, as you pointed out some time ago,
    should be as small as possible.

    That's not what I said, which you have clearly misunderstood.

    Perhaps JL would like to elaborate on what he means by two FETs in anti-parallel. How would you drive the gate of the other FET?

    The same way as you drive the gate of a single FET, from the error
    signal coming out of the rectifier-filter-integrator stage, but with
    opposite polarity and with a DC offset reflecting differences in the FET
    gate on-voltages (which have a fairly large production tolerance).

    It call for a fairly elaborate setting up procedure and microcontroller
    and a DAC or two to make it work = loads of components.

    So I'd concentrate on the oscillator distortion level rather than the gain controller contribution if I wanted to attempt better
    than 120dB.

    And you'd probably better dump LTSpice 24.1 - it has been claimed that it has a serious bug.

    Could you please provide a reference to this claim.

    My informant said it had come up on the LTSpice user's group, wherever
    that is.


    Who has claimed that it has a serious bug and is there an online discussion anywhere?

    Obviously there is, but I don't know where it is.

    Exactly what is this serious bug other than the fact that your circuit gets completely different results?

    I'm not claiming that this is the result of the bug - whatever it is -
    just raising it as a possibility.

    That might explain why your simulations of my circuit run a thousand times slower for you than they do for me and a couple of
    other people.

    There is obviously a big difference but I have not so far seen any evidence to confirm that it is a serious bug.

    No surprise there.

    --
    Bill Sloman, Sydney

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)