• Not particularly low distortion 1kHz sine wave oscillator

    From Bill Sloman@21:1/5 to All on Wed Dec 4 15:12:24 2024
    Edward Rawde has posted a number of low distortion 1kHz sine wave
    oscillators as LTSpice simulation, and John May has posted a couple of
    much low distortion examples.

    As designs they are bit opaque. I've posted my own attempts.

    Here's another.

    It doesn't perform all that well. The second harmonic is only 70dB below
    the fundamental, and te third harmonic only 67dB down.

    There are lots of components, but they are all doing exactly what I want
    them to.

    U9 is the core of the oscillator as an inverting Wein bridge. U9
    provides the controllable inverting gain that makes the Wein bridge work.

    J1 controls the gain. U8 tracks the voltage across J1 so that the gain
    control voltage on the gate tracks the voltage in the middle of the FET channel. In the circuit posted the gate sits a -4.03V and varies by
    16.2mV across the each millisecond of the cycle. The variation includes
    a 1.94mV 2kHz component which is most positive when the current in the
    FET channel is highest - +504uA and -504uA. This took some doing.

    The mechanism is the rest of the circuit.

    U1 is the core of a precise half-wave rectifier. U2 adds the output
    voltage to this signal to get a full-wave rectified output, which is
    smoothed by C22 to give about 190mV of mostly 2kHz ripple on top of a
    800mV DC signal

    This is low pass filtered by a 4-pole Bessel Sallen and Keys active
    filter around U6 and U7 whose propagation delay was carefully adjusted
    to get the phase of 2kHz component in the Fet gate drive where I wanted it.

    The integrator around U5 compares the DC component in the output of U7
    with the 1.250V component coming out of the voltage reference U4 to
    generate the gain control voltage.

    R10 puts a phase advance into the integrator output which stabilises the amplitude control feedback loop.

    R27 turns this output into a current which is fed through Q3 into the
    current mirror formed by Q1 and Q2, to create the gain control voltage
    across R11 and R21.

    It's more complicated than it has to be, but keeps the amplitude control
    loop out of saturation during start-up.

    I've got better distortion levels by largely cancelling the 2kHz in the
    FET gate control voltage, but that was even messier.

    There are better ways of doing it. John May has come up with a
    mult-phase rectification circuit which is very elegant and gets the
    distortion levels below 150dB in real life.

    I'm postig this mainly as an example of circuit design in action - I've
    gone as far down a particular rabbit hole as I reasonably can and I am
    at the point of starting over.

    Version 4
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    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 njf -1376 -1584 R0
    SYMATTR InstName J1
    SYMATTR Value MMBF4391
    SYMBOL References\\LTC6655-1.25 2560 -1120 R0
    SYMATTR InstName U4
    SYMBOL OpAmps\\opamp2 -656 -1504 R0
    WINDOW 3 13 108 Left 2
    SYMATTR Value LME49710
    SYMATTR InstName U9
    SYMATTR SpiceModel LME49710
    SYMBOL res -1200 -1664 R0
    WINDOW 0 41 37 Left 2
    WINDOW 3 36 71 Left 2
    SYMATTR InstName R7
    SYMATTR Value 470
    SYMATTR SpiceLine tol=0.1
    SYMBOL cap -64 -1824 R90
    WINDOW 0 0 32 VBottom 2
    WINDOW 3 32 32 VTop 2
    SYMATTR InstName C9
    SYMATTR Value 10p
    SYMBOL FerriteBead 576 -1936 R0
    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 res -944 -1728 R90
    WINDOW 0 0 56 VBottom 2
    WINDOW 3 32 56 VTop 2
    SYMATTR InstName R6
    SYMATTR Value 82
    SYMATTR SpiceLine tol=1
    SYMBOL cap 704 -1088 R90
    WINDOW 0 0 32 VBottom 2
    WINDOW 3 32 32 VTop 2
    SYMATTR InstName C13
    SYMATTR Value 10p
    SYMBOL res 2784 -1312 R0
    WINDOW 0 41 37 Left 2
    WINDOW 3 36 71 Left 2
    SYMATTR InstName R9
    SYMATTR Value 120k
    SYMATTR SpiceLine tol=0.1
    SYMBOL FerriteBead -1328 -1648 R0
    SYMATTR InstName L1
    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 512 -816 R90
    WINDOW 0 -16 0 VBottom 2
    SYMATTR InstName L10
    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 -224 -1712 R90
    WINDOW 0 -16 0 VBottom 2
    SYMATTR InstName L11
    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 2592 -1792 R90
    WINDOW 0 0 56 VBottom 2
    WINDOW 3 32 56 VTop 2
    SYMATTR InstName R12
    SYMATTR Value 150k
    SYMBOL res 1376 -1776 R90
    WINDOW 0 0 56 VBottom 2
    WINDOW 3 32 56 VTop 2
    SYMATTR InstName R8
    SYMATTR Value 14k
    SYMBOL res 1216 -1456 R0
    SYMATTR InstName R13
    SYMATTR Value 56k
    SYMBOL cap 1312 -1392 R0
    SYMATTR InstName C3
    SYMATTR Value 15n
    SYMBOL cap 1056 -1856 R0
    SYMATTR InstName C12
    SYMATTR Value 15n
    SYMBOL res 1216 -1568 R90
    WINDOW 0 0 56 VBottom 2
    WINDOW 3 32 56 VTop 2
    SYMATTR InstName R14
    SYMATTR Value 11.8k
    SYMBOL Opamps\\LT1013 1392 -1632 R0
    SYMATTR InstName U6
    SYMBOL res 896 -1536 R270
    WINDOW 0 32 56 VTop 2
    WINDOW 3 0 56 VBottom 2
    SYMATTR InstName R15
    SYMATTR Value 15.8k
    SYMBOL res 2048 -1840 R90
    WINDOW 0 0 56 VBottom 2
    WINDOW 3 32 56 VTop 2
    SYMATTR InstName R16
    SYMATTR Value 14k
    SYMBOL cap 1728 -1872 R0
    SYMATTR InstName C14
    SYMATTR Value 15n
    SYMBOL res 1888 -1584 R90
    WINDOW 0 0 56 VBottom 2
    WINDOW 3 32 56 VTop 2
    SYMATTR InstName R17
    SYMATTR Value 11.8k
    SYMBOL Opamps\\LT1013 2064 -1648 R0
    SYMATTR InstName U7
    SYMBOL res 1568 -1552 R270
    WINDOW 0 32 56 VTop 2
    WINDOW 3 0 56 VBottom 2
    SYMATTR InstName R18
    SYMATTR Value 15.8k
    SYMBOL res 1888 -1408 R0
    SYMATTR InstName R19
    SYMATTR Value 56k
    SYMBOL cap 1984 -1344 R0
    SYMATTR InstName C24
    SYMATTR Value 15n
    SYMBOL current 2224 -1632 R0
    WINDOW 123 0 0 Left 0
    WINDOW 39 0 0 Left 0
    SYMATTR InstName I1
    SYMATTR Value PULSE(0 -0.03mA 1ms 0.5ms 0.5ms 20ms 1 75)
    SYMBOL npn -1584 -1120 R0
    SYMATTR InstName Q1
    SYMATTR Value BC847A
    SYMBOL npn -1712 -1120 M0
    SYMATTR InstName Q2
    SYMATTR Value BC847A
    SYMBOL res -1536 -960 R0
    WINDOW 0 41 37 Left 2
    WINDOW 3 36 71 Left 2
    SYMATTR InstName R20
    SYMATTR Value 1.2k
    SYMATTR SpiceLine tol=0.1
    SYMBOL res -1792 -960 R0
    WINDOW 0 41 37 Left 2
    WINDOW 3 36 71 Left 2
    SYMATTR InstName R23
    SYMATTR Value 1.2k
    SYMATTR SpiceLine tol=0.1
    SYMBOL FerriteBead -1776 -976 R0
    SYMATTR InstName L12
    SYMATTR Value 14µ
    SYMATTR SpiceLine Ipk=3 Rser=0.0122 Rpar=870 Cpar=1000f mfg="Würth
    Elektronik" pn="7427503 WE-UKW 40060"
    SYMBOL FerriteBead -1520 -976 R0
    SYMATTR InstName L14
    SYMATTR Value 14µ
    SYMATTR SpiceLine Ipk=3 Rser=0.0122 Rpar=870 Cpar=1000f
    TEXT -1424 -776 Left 2 !.MODEL BAS70L D \n+ IS = 3.22E-9 \n+ N = 1.018
    \n+ BV = 77 \n+ IBV = 1.67E-7 \n+ RS = 20.89 \n+ CJO = 1.608E-12 \n+ VJ
    = 0.3891 \n+ M = 0.3683 \n+ FC = 0.5 \n+ EG = 0.69 \n+ XTI = 2 \n.ENDS
    TEXT -336 -528 Left 2 ;R2 a,b,c, Vishay Beschlag ACAS06S0830372P1AT
    precision 10k resistor array \n R1a, R1b Maxim MAX5492LB10000+T 10K
    resistive divider in a SOT-23-5 package
    TEXT -720 -464 Left 2 !.MODEL MMBF4391 NJF VTO=-4.6 BETA=0.02779
    LAMBDA=0.00595 RD=1 RS=1 IS=1e-14 CGD=14p CGS=10.5p PB=1 B=1 KF=1e-18
    AF=1 FC=0.5 mfg=Motorola
    TEXT -720 -408 Left 2 !.lib LME49710.lib
    TEXT -1112 -464 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 Dec 4 00:29:36 2024
    "Bill Sloman" <bill.sloman@ieee.org> wrote in message news:viokrg$l9s1$1@dont-email.me...
    Edward Rawde has posted a number of low distortion 1kHz sine wave oscillators as LTSpice simulation, and John May has posted a
    couple of much low distortion examples.

    As designs they are bit opaque. I've posted my own attempts.

    Here's another.

    Are you sure that's the correct circuit Bill?

    What I'm seeing has U1 displaced but easy to correct but U2 output is not connected and the feedback from U5 is hanging in mid air
    above an unconnected current mirror with nothing connected the the FET gate circuit.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Bill Sloman@21:1/5 to Edward Rawde on Wed Dec 4 17:35:59 2024
    On 4/12/2024 4:29 pm, Edward Rawde wrote:
    "Bill Sloman" <bill.sloman@ieee.org> wrote in message news:viokrg$l9s1$1@dont-email.me...
    Edward Rawde has posted a number of low distortion 1kHz sine wave oscillators as LTSpice simulation, and John May has posted a
    couple of much low distortion examples.

    As designs they are bit opaque. I've posted my own attempts.

    Here's another.

    Are you sure that's the correct circuit Bill?

    What I'm seeing has U1 displaced but easy to correct but U2 output is not connected and the feedback from U5 is hanging in mid air
    above an unconnected current mirror with nothing connected the the FET gate circuit.

    It probably isn't. Here's much the same circuit tweaked to give the 1kz fundamental closer to 0 dB - 1V rms. The extra componets are R8, R9 and
    R28 at the top right of the circuit.

    Version 4
    SHEET 1 3608 920
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    WIRE -1104 -2176 -1408 -2176
    WIRE -736 -2176 -1104 -2176
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    WIRE 208 -2176 -320 -2176
    WIRE 336 -2176 208 -2176
    WIRE 576 -2176 336 -2176
    WIRE -736 -2160 -736 -2176
    WIRE 208 -2160 208 -2176
    WIRE -320 -2144 -320 -2176
    WIRE 3136 -2064 -1776 -2064
    WIRE -736 -2032 -736 -2096
    WIRE -656 -2032 -736 -2032
    WIRE -320 -2032 -320 -2080
    WIRE -176 -2032 -320 -2032
    WIRE 208 -2016 208 -2096
    WIRE 336 -2016 208 -2016
    WIRE -320 -2000 -320 -2032
    WIRE -736 -1984 -736 -2032
    WIRE 336 -1968 336 -2016
    WIRE 576 -1968 576 -2176
    WIRE 1952 -1920 1744 -1920
    WIRE 2160 -1920 1952 -1920
    WIRE 1376 -1904 1072 -1904
    WIRE 1536 -1904 1376 -1904
    WIRE 336 -1888 336 -1904
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    WIRE -32 -1872 -528 -1872
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    WIRE -320 -1216 -560 -1216
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    WIRE 496 -1216 496 -1312
    WIRE 496 -1216 432 -1216
    WIRE 544 -1216 496 -1216
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    FLAG 464 -1152 0
    FLAG -48 -1024 0
    FLAG -1264 -992 0
    FLAG 336 -2176 Vcc
    FLAG 416 -624 Vee
    FLAG -560 -1152 0
    FLAG 16 -1520 Vout
    FLAG 2576 -960 0
    FLAG -1536 -1520 Fet-gate
    FLAG 2432 -1456 Vcc
    FLAG -1040 -832 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 -1616 -1312 0
    FLAG 2432 -1584 0
    SYMBOL Opamps\\LT1360 208 -1248 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 -1344 R0
    WINDOW 3 -89 62 Left 2
    WINDOW 0 -92 37 Left 2
    SYMATTR Value BAS70L
    SYMATTR InstName D1
    SYMBOL schottky 352 -944 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 704 -832 R90
    WINDOW 0 0 32 VBottom 2
    WINDOW 3 32 32 VTop 2
    SYMATTR InstName C2
    SYMATTR Value 22n
    SYMATTR SpiceLine Rser=10 Lser=6n
    SYMBOL cap 192 -1056 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 OpAmps\\opamp2 -176 -1584 R0
    WINDOW 3 13 108 Left 2
    SYMATTR Value LME49710
    SYMATTR InstName U3
    SYMATTR SpiceModel LME49710
    SYMBOL voltage -1104 -1120 R0
    WINDOW 123 0 0 Left 0
    WINDOW 39 0 0 Left 0
    SYMATTR InstName V1
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    SYMBOL voltage -1104 -976 R0
    WINDOW 123 0 0 Left 0
    WINDOW 39 0 0 Left 0
    SYMATTR InstName V2
    SYMATTR Value 12
    SYMBOL cap -480 -1552 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 -1520 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 100n
    SYMBOL res 2848 -1760 R270
    WINDOW 0 32 56 VTop 2
    WINDOW 3 0 56 VBottom 2
    SYMATTR InstName R10
    SYMATTR Value 68k
    SYMBOL Opamps\\LT1056A 2992 -1456 R0
    SYMATTR InstName U5
    SYMBOL cap 2784 -1120 R0
    SYMATTR InstName C10
    SYMATTR Value 3.3µ
    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 res -1600 -1360 R180
    WINDOW 0 31 76 Left 2
    WINDOW 3 31 40 Left 2
    SYMATTR InstName R11
    SYMATTR Value 10k
    SYMATTR SpiceLine tol=0.1
    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
    SYMBOL cap -336 -1168 R0
    WINDOW 0 -60 15 Left 2
    WINDOW 3 -62 54 Left 2
    SYMATTR InstName C18
    SYMATTR Value 100n
    SYMBOL res -1632 -1664 R0
    WINDOW 0 43 37 Left 2
    WINDOW 3 47 73 Left 2
    SYMATTR InstName R21
    SYMATTR Value 10k
    SYMATTR SpiceLine tol=0.1
    SYMBOL cap 2272 -1184 R0
    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 -512 -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 -2112 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 -2128 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 OpAmps\\opamp2 -1408 -1792 M0
    WINDOW 3 10 108 Left 2
    SYMATTR Value LME49710
    SYMATTR InstName U8
    SYMATTR SpiceModel LME49710
    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 4.87k
    SYMATTR SpiceLine tol=1
    SYMBOL cap -784 -1584 R90
    WINDOW 0 0 32 VBottom 2
    WINDOW 3 32 32 VTop 2
    SYMATTR InstName C19
    SYMATTR Value 10p
    SYMBOL FerriteBead 208 -672 R0
    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 -2128 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 njf -1376 -1584 R0
    SYMATTR InstName J1
    SYMATTR Value MMBF4391
    SYMBOL References\\LTC6655-1.25 2560 -1120 R0
    SYMATTR InstName U4
    SYMBOL OpAmps\\opamp2 -656 -1504 R0
    WINDOW 3 13 108 Left 2
    SYMATTR Value LME49710
    SYMATTR InstName U9
    SYMATTR SpiceModel LME49710
    SYMBOL res -1200 -1664 R0
    WINDOW 0 41 37 Left 2
    WINDOW 3 36 71 Left 2
    SYMATTR InstName R7
    SYMATTR Value 470
    SYMATTR SpiceLine tol=0.1
    SYMBOL cap -64 -1824 R90
    WINDOW 0 0 32 VBottom 2
    WINDOW 3 32 32 VTop 2
    SYMATTR InstName C9
    SYMATTR Value 10p
    SYMBOL FerriteBead 576 -1936 R0
    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 res -944 -1728 R90
    WINDOW 0 0 56 VBottom 2
    WINDOW 3 32 56 VTop 2
    SYMATTR InstName R6
    SYMATTR Value 82
    SYMATTR SpiceLine tol=1
    SYMBOL cap 704 -1088 R90
    WINDOW 0 0 32 VBottom 2
    WINDOW 3 32 32 VTop 2
    SYMATTR InstName C13
    SYMATTR Value 10p
    SYMBOL FerriteBead -1328 -1648 R0
    SYMATTR InstName L1
    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 512 -816 R90
    WINDOW 0 -16 0 VBottom 2
    SYMATTR InstName L10
    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 -224 -1712 R90
    WINDOW 0 -16 0 VBottom 2
    SYMATTR InstName L11
    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 2592 -1792 R90
    WINDOW 0 0 56 VBottom 2
    WINDOW 3 32 56 VTop 2
    SYMATTR InstName R12
    SYMATTR Value 137k
    SYMBOL res 1376 -1776 R90
    WINDOW 0 0 56 VBottom 2
    WINDOW 3 32 56 VTop 2
    SYMATTR InstName R8
    SYMATTR Value 14k
    SYMBOL res 1216 -1456 R0
    SYMATTR InstName R13
    SYMATTR Value 56k
    SYMBOL cap 1312 -1392 R0
    SYMATTR InstName C3
    SYMATTR Value 15n
    SYMBOL cap 1056 -1856 R0
    SYMATTR InstName C12
    SYMATTR Value 15n
    SYMBOL res 1216 -1568 R90
    WINDOW 0 0 56 VBottom 2
    WINDOW 3 32 56 VTop 2
    SYMATTR InstName R14
    SYMATTR Value 11.8k
    SYMBOL Opamps\\LT1013 1392 -1632 R0
    SYMATTR InstName U6
    SYMBOL res 896 -1536 R270
    WINDOW 0 32 56 VTop 2
    WINDOW 3 0 56 VBottom 2
    SYMATTR InstName R15
    SYMATTR Value 15.8k
    SYMBOL res 2048 -1840 R90
    WINDOW 0 0 56 VBottom 2
    WINDOW 3 32 56 VTop 2
    SYMATTR InstName R16
    SYMATTR Value 14k
    SYMBOL cap 1728 -1872 R0
    SYMATTR InstName C14
    SYMATTR Value 15n
    SYMBOL res 1888 -1584 R90
    WINDOW 0 0 56 VBottom 2
    WINDOW 3 32 56 VTop 2
    SYMATTR InstName R17
    SYMATTR Value 11.8k
    SYMBOL Opamps\\LT1013 2064 -1648 R0
    SYMATTR InstName U7
    SYMBOL res 1568 -1552 R270
    WINDOW 0 32 56 VTop 2
    WINDOW 3 0 56 VBottom 2
    SYMATTR InstName R18
    SYMATTR Value 15.8k
    SYMBOL res 1888 -1408 R0
    SYMATTR InstName R19
    SYMATTR Value 56k
    SYMBOL cap 1984 -1344 R0
    SYMATTR InstName C24
    SYMATTR Value 15n
    SYMBOL npn -1584 -1120 R0
    SYMATTR InstName Q1
    SYMATTR Value BC847A
    SYMBOL npn -1712 -1120 M0
    SYMATTR InstName Q2
    SYMATTR Value BC847A
    SYMBOL res -1536 -960 R0
    WINDOW 0 41 37 Left 2
    WINDOW 3 36 71 Left 2
    SYMATTR InstName R20
    SYMATTR Value 1.2k
    SYMATTR SpiceLine tol=0.1
    SYMBOL res -1792 -960 R0
    WINDOW 0 41 37 Left 2
    WINDOW 3 36 71 Left 2
    SYMATTR InstName R23
    SYMATTR Value 1.2k
    SYMATTR SpiceLine tol=0.1
    SYMBOL FerriteBead -1776 -976 R0
    SYMATTR InstName L12
    SYMATTR Value 14µ
    SYMATTR SpiceLine Ipk=3 Rser=0.0122 Rpar=870 Cpar=1000f mfg="Würth
    Elektronik" pn="7427503 WE-UKW 40060"
    SYMBOL FerriteBead -1520 -976 R0
    SYMATTR InstName L14
    SYMATTR Value 14µ
    SYMATTR SpiceLine Ipk=3 Rser=0.0122 Rpar=870 Cpar=1000f
    SYMBOL res -2000 -1840 R0
    WINDOW 0 43 37 Left 2
    WINDOW 3 47 73 Left 2
    SYMATTR InstName R24
    SYMATTR Value 20k
    SYMATTR SpiceLine tol=0.1
    SYMBOL res -2000 -960 R0
    WINDOW 0 43 37 Left 2
    WINDOW 3 47 73 Left 2
    SYMATTR InstName R25
    SYMATTR Value 10k
    SYMATTR SpiceLine tol=0.1
    SYMBOL pnp -1840 -1472 M180
    SYMATTR InstName Q3
    SYMBOL cap -1840 -1376 R90
    WINDOW 0 0 32 VBottom 2
    WINDOW 3 32 32 VTop 2
    SYMATTR InstName C25
    SYMATTR Value 100n
    SYMBOL res -1792 -1840 R0
    WINDOW 0 43 37 Left 2
    WINDOW 3 47 73 Left 2
    SYMATTR InstName R27
    SYMATTR Value 6.8k
    SYMATTR SpiceLine tol=0.1
    SYMBOL res 2384 -1792 R90
    WINDOW 0 0 56 VBottom 2
    WINDOW 3 32 56 VTop 2
    SYMATTR InstName R9
    SYMATTR Value 17k
    SYMBOL res 2416 -1728 R0
    SYMATTR InstName R28
    SYMATTR Value 68k
    TEXT -1424 -776 Left 2 !.MODEL BAS70L D \n+ IS = 3.22E-9 \n+ N = 1.018
    \n+ BV = 77 \n+ IBV = 1.67E-7 \n+ RS = 20.89 \n+ CJO = 1.608E-12 \n+ VJ
    = 0.3891 \n+ M = 0.3683 \n+ FC = 0.5 \n+ EG = 0.69 \n+ XTI = 2 \n.ENDS
    TEXT -336 -528 Left 2 ;R2 a,b,c, Vishay Beschlag ACAS06S0830372P1AT
    precision 10k resistor array \n R1a, R1b Maxim MAX5492LB10000+T 10K
    resistive divider in a SOT-23-5 package
    TEXT -720 -464 Left 2 !.MODEL MMBF4391 NJF VTO=-4.6 BETA=0.02779
    LAMBDA=0.00595 RD=1 RS=1 IS=1e-14 CGD=14p CGS=10.5p PB=1 B=1 KF=1e-18
    AF=1 FC=0.5 mfg=Motorola
    TEXT -720 -408 Left 2 !.lib LME49710.lib
    TEXT -1112 -464 Left 2 !.tran 0 10s 0s startup

    --
    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 Dec 4 14:10:17 2024
    "Bill Sloman" <bill.sloman@ieee.org> wrote in message news:viot8j$mt28$1@dont-email.me...
    On 4/12/2024 4:29 pm, Edward Rawde wrote:
    "Bill Sloman" <bill.sloman@ieee.org> wrote in message news:viokrg$l9s1$1@dont-email.me...
    Edward Rawde has posted a number of low distortion 1kHz sine wave oscillators as LTSpice simulation, and John May has posted a
    couple of much low distortion examples.

    As designs they are bit opaque. I've posted my own attempts.

    Here's another.

    Are you sure that's the correct circuit Bill?

    What I'm seeing has U1 displaced but easy to correct but U2 output is not connected and the feedback from U5 is hanging in mid
    air
    above an unconnected current mirror with nothing connected the the FET gate circuit.

    It probably isn't. Here's much the same circuit tweaked to give the 1kz fundamental closer to 0 dB - 1V rms. The extra componets
    are R8, R9 and R28 at the top right of the circuit.


    Ok I had to adjust the position of U1 and connect the + pin.
    FFT shows noise at 70dB down.

    I decided to find out whether a discrete circuit using a high voltage rail would have better distortion performance.
    This circuit has no gain control yet but if you take a sample when the output is at about 1V pk-pk you get 100dB down at 2kHz as
    long as you keep your fingers away from the supply rail. If I could just get rid of 2kHz it would be 130dB down.

    Version 4
    SHEET 1 2740 1600
    WIRE 288 272 224 272
    WIRE 464 272 288 272
    WIRE 752 272 464 272
    WIRE 1136 272 752 272
    WIRE 1376 272 1136 272
    WIRE 1664 272 1376 272
    WIRE 224 320 224 272
    WIRE 464 320 464 272
    WIRE 1136 320 1136 272
    WIRE 1376 320 1376 272
    WIRE 752 416 752 272
    WIRE 1664 416 1664 272
    WIRE 224 464 224 400
    WIRE 320 464 224 464
    WIRE 464 464 464 400
    WIRE 688 464 464 464
    WIRE 1136 464 1136 400
    WIRE 1232 464 1136 464
    WIRE 1376 464 1376 400
    WIRE 1600 464 1376 464
    WIRE 224 544 224 464
    WIRE 320 544 320 464
    WIRE 1136 544 1136 464
    WIRE 1232 544 1232 464
    WIRE 512 624 384 624
    WIRE 752 624 752 512
    WIRE 752 624 576 624
    WIRE 1424 624 1296 624
    WIRE 1664 624 1664 512
    WIRE 1664 624 1488 624
    WIRE -304 656 -304 608
    WIRE 464 688 464 464
    WIRE 1376 688 1376 464
    WIRE 224 736 224 624
    WIRE 384 736 384 624
    WIRE 384 736 224 736
    WIRE 400 736 384 736
    WIRE 1136 736 1136 624
    WIRE 1296 736 1296 624
    WIRE 1296 736 1136 736
    WIRE 1312 736 1296 736
    WIRE 224 768 224 736
    WIRE 1136 768 1136 736
    WIRE -304 800 -304 736
    WIRE 160 816 80 816
    WIRE 320 816 320 608
    WIRE 464 816 464 784
    WIRE 464 816 320 816
    WIRE 1072 816 992 816
    WIRE 1232 816 1232 608
    WIRE 1376 816 1376 784
    WIRE 1376 816 1232 816
    WIRE 1664 816 1664 624
    WIRE 1840 816 1664 816
    WIRE 1952 816 1840 816
    WIRE 464 832 464 816
    WIRE 1376 832 1376 816
    WIRE 752 864 752 624
    WIRE 880 864 752 864
    WIRE 80 912 80 816
    WIRE 128 912 80 912
    WIRE 224 912 224 864
    WIRE 224 912 192 912
    WIRE 992 912 992 816
    WIRE 1040 912 992 912
    WIRE 1136 912 1136 864
    WIRE 1136 912 1104 912
    WIRE 224 928 224 912
    WIRE 320 928 224 928
    WIRE 1136 928 1136 912
    WIRE 1232 928 1136 928
    WIRE 80 944 80 912
    WIRE 464 944 464 912
    WIRE 544 944 464 944
    WIRE 992 944 992 912
    WIRE 1376 944 1376 912
    WIRE 1456 944 1376 944
    WIRE 224 960 224 928
    WIRE 464 960 464 944
    WIRE 1136 960 1136 928
    WIRE 1376 960 1376 944
    WIRE 752 976 752 864
    WIRE 752 976 640 976
    WIRE 1664 976 1664 816
    WIRE 1664 976 1552 976
    WIRE 1664 992 1664 976
    WIRE 1776 992 1664 992
    WIRE 640 1024 640 976
    WIRE 1552 1024 1552 976
    WIRE 1776 1024 1776 992
    WIRE 80 1072 80 1024
    WIRE 464 1072 464 1040
    WIRE 464 1072 80 1072
    WIRE 992 1072 992 1024
    WIRE 1376 1072 1376 1040
    WIRE 1376 1072 992 1072
    WIRE 224 1104 224 1040
    WIRE 224 1104 80 1104
    WIRE 1136 1104 1136 1040
    WIRE 1136 1104 992 1104
    WIRE 80 1136 80 1104
    WIRE 224 1136 224 1104
    WIRE 464 1136 464 1072
    WIRE 544 1136 544 944
    WIRE 752 1136 752 976
    WIRE 992 1136 992 1104
    WIRE 1136 1136 1136 1104
    WIRE 1376 1136 1376 1072
    WIRE 1456 1136 1456 944
    WIRE 1664 1136 1664 992
    WIRE 80 1248 80 1200
    WIRE 80 1248 48 1248
    WIRE 224 1248 224 1216
    WIRE 224 1248 80 1248
    WIRE 464 1248 464 1216
    WIRE 464 1248 224 1248
    WIRE 544 1248 544 1200
    WIRE 544 1248 464 1248
    WIRE 752 1248 752 1216
    WIRE 752 1248 544 1248
    WIRE 992 1248 992 1200
    WIRE 992 1248 752 1248
    WIRE 1136 1248 1136 1216
    WIRE 1136 1248 992 1248
    WIRE 1376 1248 1376 1216
    WIRE 1376 1248 1136 1248
    WIRE 1456 1248 1456 1200
    WIRE 1456 1248 1376 1248
    WIRE 1664 1248 1664 1216
    WIRE 1664 1248 1456 1248
    WIRE 48 1264 48 1248
    WIRE 320 1328 320 928
    WIRE 368 1328 320 1328
    WIRE 640 1328 640 1088
    WIRE 640 1328 448 1328
    WIRE 880 1328 880 864
    WIRE 976 1328 880 1328
    WIRE 1056 1328 1040 1328
    WIRE 1232 1328 1232 928
    WIRE 1232 1328 1136 1328
    WIRE 1312 1328 1232 1328
    WIRE 1360 1328 1312 1328
    WIRE 1504 1328 1440 1328
    WIRE 1552 1328 1552 1088
    WIRE 1552 1328 1504 1328
    WIRE 1312 1424 1312 1328
    WIRE 1376 1424 1312 1424
    WIRE 1504 1424 1504 1328
    WIRE 1504 1424 1440 1424
    WIRE 320 1520 320 1328
    WIRE 688 1520 320 1520
    WIRE 1776 1520 1776 1088
    WIRE 1776 1520 768 1520
    FLAG -304 800 0
    FLAG -304 608 V+
    FLAG 48 1264 0
    FLAG 288 272 V+
    FLAG 1840 816 output
    DATAFLAG 704 624 "round(($)*100)/100"
    DATAFLAG 512 944 "round(($)*100)/100"
    DATAFLAG 416 1072 "round(($)*100)/100"
    DATAFLAG 128 816 "round(($)*100)/100"
    DATAFLAG 272 928 "round(($)*100)/100"
    DATAFLAG 176 1104 "round(($)*100)/100"
    DATAFLAG 272 464 "round(($)*100)/100"
    DATAFLAG 272 736 "round(($)*100)/100"
    DATAFLAG 416 816 "round(($)*100)/100"
    DATAFLAG 512 464 "round(($)*100)/100"
    DATAFLAG 1616 624 "round(($)*100)/100"
    DATAFLAG 1424 944 "round(($)*100)/100"
    DATAFLAG 1328 1072 "round(($)*100)/100"
    DATAFLAG 1040 816 "round(($)*100)/100"
    DATAFLAG 1184 928 "round(($)*100)/100"
    DATAFLAG 1088 1104 "round(($)*100)/100"
    DATAFLAG 1184 464 "round(($)*100)/100"
    DATAFLAG 1184 736 "round(($)*100)/100"
    DATAFLAG 1328 816 "round(($)*100)/100"
    DATAFLAG 1424 464 "round(($)*100)/100"
    SYMBOL voltage -304 640 R0
    WINDOW 123 0 0 Left 0
    WINDOW 39 10 135 Left 2
    WINDOW 0 12 7 Left 2
    WINDOW 3 15 104 Left 2
    SYMATTR InstName V1
    SYMATTR Value 96
    SYMBOL res 784 1504 R90
    WINDOW 0 0 56 VBottom 2
    WINDOW 3 32 56 VTop 2
    SYMATTR InstName R14
    SYMATTR Value 9841
    SYMBOL res 208 304 R0
    WINDOW 3 36 73 Left 2
    SYMATTR Value 47k
    SYMATTR InstName R10
    SYMBOL npn 160 768 R0
    SYMATTR InstName Q1
    SYMATTR Value BC846B
    SYMBOL res 208 528 R0
    WINDOW 0 -41 35 Left 2
    WINDOW 3 -64 67 Left 2
    SYMATTR InstName R11
    SYMATTR Value 150k
    SYMBOL npn 688 416 R0
    SYMATTR InstName Q2
    SYMATTR Value BC846B
    SYMBOL res 448 304 R0
    WINDOW 3 35 73 Left 2
    SYMATTR Value 22k
    SYMATTR InstName R15
    SYMBOL npn 400 688 R0
    SYMATTR InstName Q3
    SYMATTR Value BC846B
    SYMBOL polcap 304 544 R0
    SYMATTR InstName C1
    SYMATTR Value 1µ
    SYMBOL res 208 944 R0
    WINDOW 3 35 67 Left 2
    SYMATTR Value 470
    SYMATTR InstName R16
    SYMBOL res 208 1120 R0
    WINDOW 3 37 67 Left 2
    SYMATTR Value 39k
    SYMATTR InstName R19
    SYMBOL res 64 928 R0
    WINDOW 0 -41 40 Left 2
    WINDOW 3 -66 68 Left 2
    SYMATTR InstName R20
    SYMATTR Value 270k
    SYMBOL cap 192 896 R90
    WINDOW 0 0 32 VBottom 2
    WINDOW 3 32 32 VTop 2
    SYMATTR InstName C6
    SYMATTR Value 470p
    SYMBOL polcap 64 1136 R0
    SYMATTR InstName C7
    SYMATTR Value 22µ
    SYMBOL res 736 1120 R0
    WINDOW 0 36 38 Left 2
    WINDOW 3 36 72 Left 2
    SYMATTR InstName R21
    SYMATTR Value 3.3k
    SYMBOL cap 576 608 R90
    WINDOW 0 0 32 VBottom 2
    WINDOW 3 32 32 VTop 2
    SYMATTR InstName C8
    SYMATTR Value 10p
    SYMBOL res 448 944 R0
    WINDOW 0 -52 35 Left 2
    WINDOW 3 -54 62 Left 2
    SYMATTR InstName R22
    SYMATTR Value 5.6k
    SYMBOL res 448 1120 R0
    WINDOW 0 -53 28 Left 2
    WINDOW 3 -50 58 Left 2
    SYMATTR InstName R23
    SYMATTR Value 6.8k
    SYMBOL res 448 816 R0
    WINDOW 0 -59 43 Left 2
    WINDOW 3 -59 70 Left 2
    SYMATTR InstName R24
    SYMATTR Value 2.2k
    SYMBOL res 464 1312 R90
    WINDOW 0 0 56 VBottom 2
    WINDOW 3 32 56 VTop 2
    SYMATTR InstName R25
    SYMATTR Value 10k
    SYMBOL polcap 624 1024 R0
    SYMATTR InstName C11
    SYMATTR Value 1µ
    SYMBOL polcap 528 1136 R0
    SYMATTR InstName C12
    SYMATTR Value 100µ
    SYMBOL res 1344 1344 R270
    WINDOW 0 32 56 VTop 2
    WINDOW 3 0 56 VBottom 2
    SYMATTR InstName R13
    SYMATTR Value 16K
    SYMBOL res 1152 1312 R90
    WINDOW 0 0 56 VBottom 2
    WINDOW 3 32 56 VTop 2
    SYMATTR InstName R26
    SYMATTR Value 8K
    SYMBOL cap 1376 1440 R270
    WINDOW 0 32 32 VTop 2
    WINDOW 3 0 32 VBottom 2
    SYMATTR InstName C5
    SYMATTR Value 10n
    SYMBOL cap 1040 1312 R90
    WINDOW 0 0 32 VBottom 2
    WINDOW 3 32 32 VTop 2
    SYMATTR InstName C9
    SYMATTR Value 20n
    SYMBOL res 1120 304 R0
    WINDOW 3 36 73 Left 2
    SYMATTR Value 47k
    SYMATTR InstName R29
    SYMBOL npn 1072 768 R0
    SYMATTR InstName Q4
    SYMATTR Value BC846B
    SYMBOL res 1120 528 R0
    WINDOW 0 -41 35 Left 2
    WINDOW 3 -64 67 Left 2
    SYMATTR InstName R30
    SYMATTR Value 150k
    SYMBOL npn 1600 416 R0
    SYMATTR InstName Q5
    SYMATTR Value BC846B
    SYMBOL res 1360 304 R0
    WINDOW 3 35 73 Left 2
    SYMATTR Value 22k
    SYMATTR InstName R31
    SYMBOL npn 1312 688 R0
    SYMATTR InstName Q6
    SYMATTR Value BC846B
    SYMBOL polcap 1216 544 R0
    SYMATTR InstName C10
    SYMATTR Value 1µ
    SYMBOL res 1120 944 R0
    WINDOW 3 35 67 Left 2
    SYMATTR Value 470
    SYMATTR InstName R32
    SYMBOL res 1120 1120 R0
    WINDOW 3 37 67 Left 2
    SYMATTR Value 39k
    SYMATTR InstName R33
    SYMBOL res 976 928 R0
    WINDOW 0 -41 40 Left 2
    WINDOW 3 -66 68 Left 2
    SYMATTR InstName R34
    SYMATTR Value 270k
    SYMBOL cap 1104 896 R90
    WINDOW 0 0 32 VBottom 2
    WINDOW 3 32 32 VTop 2
    SYMATTR InstName C13
    SYMATTR Value 470p
    SYMBOL polcap 976 1136 R0
    SYMATTR InstName C14
    SYMATTR Value 22µ
    SYMBOL res 1648 1120 R0
    WINDOW 0 36 38 Left 2
    WINDOW 3 36 72 Left 2
    SYMATTR InstName R35
    SYMATTR Value 3.3k
    SYMBOL cap 1488 608 R90
    WINDOW 0 0 32 VBottom 2
    WINDOW 3 32 32 VTop 2
    SYMATTR InstName C15
    SYMATTR Value 10p
    SYMBOL res 1360 944 R0
    WINDOW 0 -52 35 Left 2
    WINDOW 3 -54 62 Left 2
    SYMATTR InstName R36
    SYMATTR Value 5.6k
    SYMBOL res 1360 1120 R0
    WINDOW 0 -53 28 Left 2
    WINDOW 3 -50 58 Left 2
    SYMATTR InstName R37
    SYMATTR Value 6.8k
    SYMBOL res 1360 816 R0
    WINDOW 0 -59 43 Left 2
    WINDOW 3 -59 70 Left 2
    SYMATTR InstName R38
    SYMATTR Value 2.2k
    SYMBOL polcap 1536 1024 R0
    SYMATTR InstName C16
    SYMATTR Value 1µ
    SYMBOL polcap 1440 1136 R0
    SYMATTR InstName C17
    SYMATTR Value 100µ
    SYMBOL polcap 1760 1024 R0
    SYMATTR InstName C2
    SYMATTR Value 1µ
    TEXT -608 1224 Left 2 !.tran 0 4 2.5 1u
    TEXT -608 1176 Left 2 !.options plotwinsize=0 numdgt=7 method=trap
    TEXT -408 440 Left 2 ;1kHz low distortion sinewave oscillator.
    TEXT -400 472 Left 2 ;2 Dec 2024.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From john larkin@21:1/5 to invalid@invalid.invalid on Sat Dec 21 14:49:09 2024
    On Wed, 4 Dec 2024 14:10:17 -0500, "Edward Rawde"
    <invalid@invalid.invalid> wrote:

    "Bill Sloman" <bill.sloman@ieee.org> wrote in message news:viot8j$mt28$1@dont-email.me...
    On 4/12/2024 4:29 pm, Edward Rawde wrote:
    "Bill Sloman" <bill.sloman@ieee.org> wrote in message news:viokrg$l9s1$1@dont-email.me...
    Edward Rawde has posted a number of low distortion 1kHz sine wave oscillators as LTSpice simulation, and John May has posted a
    couple of much low distortion examples.

    As designs they are bit opaque. I've posted my own attempts.

    Here's another.

    Are you sure that's the correct circuit Bill?

    What I'm seeing has U1 displaced but easy to correct but U2 output is not connected and the feedback from U5 is hanging in mid
    air
    above an unconnected current mirror with nothing connected the the FET gate circuit.

    It probably isn't. Here's much the same circuit tweaked to give the 1kz fundamental closer to 0 dB - 1V rms. The extra componets
    are R8, R9 and R28 at the top right of the circuit.


    Ok I had to adjust the position of U1 and connect the + pin.
    FFT shows noise at 70dB down.

    I decided to find out whether a discrete circuit using a high voltage rail would have better distortion performance.
    This circuit has no gain control yet but if you take a sample when the output is at about 1V pk-pk you get 100dB down at 2kHz as
    long as you keep your fingers away from the supply rail. If I could just get rid of 2kHz it would be 130dB down.


    A good loop gain scheme could use a pair of jfets or mosfets connected antiparallel against ground, gates tied together to the control
    voltage.

    Nonlinearities would mostly cancel.

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