• RF Resistors

    From Artist@21:1/5 to All on Mon Jul 25 16:12:52 2022
    Is there still an engineering Usenet group where the vast majority of
    posts are on topic for electronic design?

    In case there are any electronic engineers still watching this group,
    here is my question:

    I need to design a TIA of bandwidth up to 5 MHz. The analog anti
    aliasing filter is to be set at 5 MHz. I would like the front end to
    have a transimpedance value of 4.02 kohm. The A to D converter's sample
    rate is to be 10 Mhz. So that the A to D conversions will alias very
    little noise in the bandwidth region 5 MHz, to 10 MHz, I need resistors
    that have self resonance well beyond 10 MHz.

    So now I am looking at HF resistors. Because noise is primarily
    determined by the gain of the first stage, it is desirable for the front
    end's feedback resistor to be 4.02 kohm.

    The Vishay FC series resistors are made in values only up to 1 kohm.
    They are very expensive, and so I am reluctant to put 4 of these 1 kohm resistors in series. They are, however, available.

    The Visay HCHP series is made in values well beyond 4.02 kohm. But I
    cannot find them on the shelf anywhere, and they are extraordinarily
    expensive. The minimum buy makes them cost prohibitive to acquire, and
    the lead times are too long.

    I would appreciate advice on any alternatives.

    I am not able to find device models for the common thin film metal
    resistors. I do not know how well they would work up to 10 MHz. I would
    like to hear from any who are experienced in using them up this frequency.

    --
    To email me directly remove sj. from my email address's domain name.
    This is a spam jammer.

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  • From Anthony William Sloman@21:1/5 to Artist on Mon Jul 25 16:51:08 2022
    On Tuesday, July 26, 2022 at 9:13:00 AM UTC+10, Artist wrote:
    Is there still an engineering Usenet group where the vast majority of
    posts are on topic for electronic design?

    In case there are any electronic engineers still watching this group,
    here is my question:

    I need to design a TIA of bandwidth up to 5 MHz. The analog anti
    aliasing filter is to be set at 5 MHz. I would like the front end to
    have a transimpedance value of 4.02 kohm. The A to D converter's sample
    rate is to be 10 MHz. So that the A to D conversions will alias very
    little noise in the bandwidth region 5 MHz, to 10 MHz, I need resistors
    that have self resonance well beyond 10 MHz.

    So now I am looking at HF resistors. Because noise is primarily
    determined by the gain of the first stage, it is desirable for the front end's feedback resistor to be 4.02 kohm.

    The Vishay FC series resistors are made in values only up to 1 kohm.
    They are very expensive, and so I am reluctant to put 4 of these 1 kohm resistors in series. They are, however, available.

    The Visay HCHP series is made in values well beyond 4.02 kohm. But I
    cannot find them on the shelf anywhere, and they are extraordinarily expensive. The minimum buy makes them cost prohibitive to acquire, and
    the lead times are too long.

    I would appreciate advice on any alternatives.


    Element 14 has Susumu 4.02k 0.1% parts in stock for less than a dollar each

    https://4donline.ihs.com/images/VipMasterIC/IC/SUSU/SUSU-S-A0004582566/SUSU-S-A0004582566-1.pdf?hkey=52A5661711E402568146F3353EA87419

    As surface mount parts they will be L-trimmed and have very little inductance or parallel capacitance. They will be fine at 5MHz, as John Larkin has pointed out. Back in the mid-1980's we got shocked when Philips put an L-trimmer surface mount roughly 1
    Megohm resistor into a video preamp and it worked fine.

    I am not able to find device models for the common thin film metal resistors. I do not know how well they would work up to 10 MHz. I would
    like to hear from any who are experienced in using them up this frequency.

    Philips - once a upon a time - published frequency response data for their spiral trimmed axial metal film resistors. The L-trimmed sufrace mount part did much better than that. Going to Vishay for you job would be an overkill.

    --
    Bill Sloman, Sydney

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  • From John Larkin@21:1/5 to All on Mon Jul 25 16:33:15 2022
    On Mon, 25 Jul 2022 16:12:52 -0700, Artist <sepflanze@sj.gmail.com>
    wrote:

    Is there still an engineering Usenet group where the vast majority of
    posts are on topic for electronic design?

    In case there are any electronic engineers still watching this group,
    here is my question:

    I need to design a TIA of bandwidth up to 5 MHz. The analog anti
    aliasing filter is to be set at 5 MHz. I would like the front end to
    have a transimpedance value of 4.02 kohm. The A to D converter's sample
    rate is to be 10 Mhz. So that the A to D conversions will alias very
    little noise in the bandwidth region 5 MHz, to 10 MHz, I need resistors
    that have self resonance well beyond 10 MHz.

    A common resistor really doesn't have a self-resonant frequency, or
    one that you'd notice.



    So now I am looking at HF resistors. Because noise is primarily
    determined by the gain of the first stage, it is desirable for the front >end's feedback resistor to be 4.02 kohm.

    The Vishay FC series resistors are made in values only up to 1 kohm.
    They are very expensive, and so I am reluctant to put 4 of these 1 kohm >resistors in series. They are, however, available.

    The Visay HCHP series is made in values well beyond 4.02 kohm. But I
    cannot find them on the shelf anywhere, and they are extraordinarily >expensive. The minimum buy makes them cost prohibitive to acquire, and
    the lead times are too long.

    I would appreciate advice on any alternatives.

    I am not able to find device models for the common thin film metal
    resistors. I do not know how well they would work up to 10 MHz. I would
    like to hear from any who are experienced in using them up this frequency.

    Ordinary surface-mount resistors will be fine at 1 GHz, much less 5
    MHz. The parallel capacitance of an 0603 is around 0.05 pF. You're
    probably putting a bigger cap in parallel in the TIA.

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  • From Phil Allison@21:1/5 to All on Mon Jul 25 16:32:57 2022
    BS Artist ? wrote:

    ==============
    Is there still an engineering Usenet group where the vast majority of
    posts are on topic for electronic design?

    In case there are any electronic engineers still watching this group,
    here is my question:

    ** Thanks for the insults.


    I need to design a TIA of bandwidth up to 5 MHz. The analog anti
    aliasing filter is to be set at 5 MHz. I would like the front end to
    have a transimpedance value of 4.02 kohm. The A to D converter's sample
    rate is to be 10 Mhz. So that the A to D conversions will alias very
    little noise in the bandwidth region 5 MHz, to 10 MHz, I need resistors
    that have self resonance well beyond 10 MHz.


    ** Where is the problem ?

    So now I am looking at HF resistors.

    ** Why?


    I am not able to find device models for the common thin film metal
    resistors. I do not know how well they would work up to 10 MHz. I would
    like to hear from any who are experienced in using them up this frequency.

    ** Ever heard of Google ?

    https://passive-components.eu/resistor-voltage-and-frequency-dependence/

    Note. The letter W has been substituted for the ohm symbol omega in the captions.


    ..... Phil

    --- SoupGate-Win32 v1.05
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  • From Artist@21:1/5 to Anthony William Sloman on Mon Jul 25 20:54:55 2022
    On 7/25/22 16:51, Anthony William Sloman wrote:
    On Tuesday, July 26, 2022 at 9:13:00 AM UTC+10, Artist wrote:
    Is there still an engineering Usenet group where the vast majority of
    posts are on topic for electronic design?

    In case there are any electronic engineers still watching this group,
    here is my question:

    I need to design a TIA of bandwidth up to 5 MHz. The analog anti
    aliasing filter is to be set at 5 MHz. I would like the front end to
    have a transimpedance value of 4.02 kohm. The A to D converter's sample
    rate is to be 10 MHz. So that the A to D conversions will alias very
    little noise in the bandwidth region 5 MHz, to 10 MHz, I need resistors
    that have self resonance well beyond 10 MHz.

    So now I am looking at HF resistors. Because noise is primarily
    determined by the gain of the first stage, it is desirable for the front
    end's feedback resistor to be 4.02 kohm.

    The Vishay FC series resistors are made in values only up to 1 kohm.
    They are very expensive, and so I am reluctant to put 4 of these 1 kohm
    resistors in series. They are, however, available.

    The Visay HCHP series is made in values well beyond 4.02 kohm. But I
    cannot find them on the shelf anywhere, and they are extraordinarily
    expensive. The minimum buy makes them cost prohibitive to acquire, and
    the lead times are too long.

    I would appreciate advice on any alternatives.


    Element 14 has Susumu 4.02k 0.1% parts in stock for less than a dollar each

    https://4donline.ihs.com/images/VipMasterIC/IC/SUSU/SUSU-S-A0004582566/SUSU-S-A0004582566-1.pdf?hkey=52A5661711E402568146F3353EA87419

    As surface mount parts they will be L-trimmed and have very little inductance or parallel capacitance. They will be fine at 5MHz, as John Larkin has pointed out. Back in the mid-1980's we got shocked when Philips put an L-trimmer surface mount roughly
    1 Megohm resistor into a video preamp and it worked fine.

    I am not able to find device models for the common thin film metal
    resistors. I do not know how well they would work up to 10 MHz. I would
    like to hear from any who are experienced in using them up this frequency.

    Philips - once a upon a time - published frequency response data for their spiral trimmed axial metal film resistors. The L-trimmed sufrace mount part did much better than that. Going to Vishay for you job would be an overkill.


    Thank you for this response. I will try this resistor.

    --
    To email me directly remove sj. from my email address's domain name.
    This is a spam jammer.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Phil Hobbs@21:1/5 to Artist on Tue Jul 26 08:34:07 2022
    Artist wrote:
    Is there still an engineering Usenet group where the vast majority of
    posts are on topic for electronic design?

    I'd recommend Guy Macon's moderated group. misc.business.product-dev,
    but it died out 15 or so years back. (Old inhabitants of SED will
    remember.)

    In case there are any electronic engineers still watching this group,
    here is my question:

    I need to design a TIA of bandwidth up to 5 MHz.

    Is it for a photodiode, or something else? The usual issue is input capacitance.

    The analog anti aliasing filter is to be set at 5 MHz. I would like
    the front end to have a transimpedance value of 4.02 kohm. The A to D converter's sample rate is to be 10 Mhz. So that the A to D
    conversions will alias very little noise in the bandwidth region 5
    MHz, to 10 MHz, I need resistors that have self resonance well beyond
    10 MHz.

    So now I am looking at HF resistors. Because noise is primarily
    determined by the gain of the first stage, it is desirable for the
    front end's feedback resistor to be 4.02 kohm.

    The Vishay FC series resistors are made in values only up to 1 kohm.
    They are very expensive, and so I am reluctant to put 4 of these 1
    kohm resistors in series. They are, however, available.

    The Visay HCHP series is made in values well beyond 4.02 kohm. But I
    cannot find them on the shelf anywhere, and they are extraordinarily
    expensive. The minimum buy makes them cost prohibitive to acquire,
    and the lead times are too long.

    I would appreciate advice on any alternatives.

    What problem are you trying to solve? As others have mentioned, you can
    use a 4k resistor up into the hundreds of megahertz with no issues. You shouldn't even notice its shunt capacitance.

    I am not able to find device models for the common thin film metal
    resistors. I do not know how well they would work up to 10 MHz. I
    would like to hear from any who are experienced in using them up this frequency.

    The main issue is that the shunt capacitance across a resistor depends
    on the configuration of nearby conductors and dielectrics.

    Last week I was tweaking up a TIA with a 10M feedback resistor that
    works up beyond 1 MHz. It uses a combination of a bootstrapped pour on
    one end of the resistor and an adjustable RC lead-lag network to flatten
    out the gain.

    From an RC point of view, that's about 500 times harder than what
    you're aiming at--the shunt capacitance of a SMT resistor all by itself
    is about 0.1 pF, and it's more like 0.05 pF when mounted on a
    ground-plane PC board. (You can measure this yourself, if you pony up
    $100 for a used Boonton 72 three-terminal capacitance meter.)

    At 4k, the RC corner frequency will be around

    f_c ~= 1/(2 pi * 4k * 100 fF) = 400 MHz,

    and probably well above that when it's board-mounted. Any bandwidth
    problems you may be having are coming from elsewhere.

    Cheers

    Phil Hobbs

    --
    Dr Philip C D Hobbs
    Principal Consultant
    ElectroOptical Innovations LLC / Hobbs ElectroOptics
    Optics, Electro-optics, Photonics, Analog Electronics
    Briarcliff Manor NY 10510

    http://electrooptical.net
    http://hobbs-eo.com

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  • From Artist@21:1/5 to Phil Allison on Tue Jul 26 10:19:30 2022
    On 7/25/22 16:32, Phil Allison wrote:
    BS Artist ? wrote:

    ==============
    Is there still an engineering Usenet group where the vast majority of
    posts are on topic for electronic design?

    In case there are any electronic engineers still watching this group,
    here is my question:

    ** Thanks for the insults.


    I need to design a TIA of bandwidth up to 5 MHz. The analog anti
    aliasing filter is to be set at 5 MHz. I would like the front end to
    have a transimpedance value of 4.02 kohm. The A to D converter's sample
    rate is to be 10 Mhz. So that the A to D conversions will alias very
    little noise in the bandwidth region 5 MHz, to 10 MHz, I need resistors
    that have self resonance well beyond 10 MHz.


    ** Where is the problem ?

    So now I am looking at HF resistors.

    ** Why?


    I am not able to find device models for the common thin film metal
    resistors. I do not know how well they would work up to 10 MHz. I would
    like to hear from any who are experienced in using them up this frequency.

    ** Ever heard of Google ?

    https://passive-components.eu/resistor-voltage-and-frequency-dependence/

    Note. The letter W has been substituted for the ohm symbol omega in the captions.


    ..... Phil

    Apologies for that.

    It had been a long time since I have been in this group. Just before
    starting this thread what I saw was spam, off topic postings, and
    nothing about electronic design. I have since seen several on topic threads.


    --
    To email me directly remove sj. from my email address's domain name.
    This is a spam jammer.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Artist@21:1/5 to Phil Hobbs on Tue Jul 26 16:00:23 2022
    On 7/26/22 05:34, Phil Hobbs wrote:
    Artist wrote:
    Is there still an engineering Usenet group where the vast majority of
     posts are on topic for electronic design?

    I'd recommend Guy Macon's moderated group. misc.business.product-dev,
    but it died out 15 or so years back.  (Old inhabitants of SED will remember.)

    In case there are any electronic engineers still watching this group,
     here is my question:

    I need to design a TIA of bandwidth up to 5 MHz.

    Is it for a photodiode, or something else?  The usual issue is input capacitance.

    The analog anti aliasing filter is to be set at 5 MHz. I would like
    the front end to have a transimpedance value of 4.02 kohm. The A to D
    converter's sample rate is to be 10 Mhz. So that the A to D
    conversions will alias very little noise in the bandwidth region 5
    MHz, to 10 MHz, I need resistors that have self resonance well beyond
    10 MHz.

    So now I am looking at HF resistors. Because noise is primarily
    determined by the gain of the first stage, it is desirable for the
    front end's feedback resistor to be 4.02 kohm.

    The Vishay FC series resistors are made in values only up to 1 kohm.
     They are very expensive, and so I am reluctant to put 4 of these 1
    kohm resistors in series. They are, however, available.

    The Visay HCHP series is made in values well beyond 4.02 kohm. But I
     cannot find them on the shelf anywhere, and they are extraordinarily
     expensive. The minimum buy makes them cost prohibitive to acquire,
    and the lead times are too long.

    I would appreciate advice on any alternatives.

    What problem are you trying to solve?  As others have mentioned, you can
    use a 4k resistor up into the hundreds of megahertz with no issues.  You shouldn't even notice its shunt capacitance.

    I am not able to find device models for the common thin film metal
    resistors. I do not know how well they would work up to 10 MHz. I
    would like to hear from any who are experienced in using them up this
    frequency.

    The main issue is that the shunt capacitance across a resistor depends
    on the configuration of nearby conductors and dielectrics.

    Last week I was tweaking up a TIA with a 10M feedback resistor that
    works up beyond 1 MHz.  It uses a combination of a bootstrapped pour on
    one end of the resistor and an adjustable RC lead-lag network to flatten
    out the gain.

    From an RC point of view, that's about 500 times harder than what
    you're aiming at--the shunt capacitance of a SMT resistor all by itself
    is about 0.1 pF, and it's more like 0.05 pF when mounted on a
    ground-plane PC board.  (You can measure this yourself, if you pony up
    $100 for a used Boonton 72 three-terminal capacitance meter.)

    At 4k, the RC corner frequency will be around

    f_c ~= 1/(2 pi * 4k * 100 fF) = 400 MHz,

    and probably well above that when it's board-mounted.  Any bandwidth problems you may be having are coming from elsewhere.

    Cheers

    Phil Hobbs


    It will be a photodiode, currently it is the OSI Optoelectronics
    InGaAs-120L-FC . This might change. https://www.osioptoelectronics.com/standard-products/ingaas-photodiodes/high-speed-ingaas.aspx

    The currently selected op amp is the LTC6226 https://www.analog.com/en/products/ltc6226.html#product-overview
    or the TMUX7462F
    https://www.ti.com/lit/ds/symlink/tmux7412f.pdf

    I would like to be able to have several gain options for the first stage
    gain from 4K all the way up to 630k. The switch in consideration for
    this is:
    MAX14777.
    https://datasheets.maximintegrated.com/en/ds/MAX14777.pdf
    TMUX7412F
    https://www.ti.com/product/TMUX7412F
    The current idea is to have a high value resistor in the vicinity of
    630k in parallel with the switches, and arrange the switches to switch a
    choice of one of 4 parallel resistors. The would provide 5 gain options.
    and more if more then one resistor is switched into the feedback path. I
    know having this option will add capacitance to the virtual ground, even
    though the analog switch would be between the op amp output, and the
    resistors.

    I am aware of your virtual ground bootstrap techniques for high
    capacitance photodiodes to raise bandwidth, and reduce noise, by
    reducing the capacitance seen by the virtual ground. I do not know right
    now if bootstraping would add more capacitance than would be reduced.

    Is the next edition of your book in which you describe bootstraping out?
    I already have the one before it.

    --
    To email me directly remove sj. from my email address's domain name.
    This is a spam jammer.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From jlarkin@highlandsniptechnology.com@21:1/5 to pallison49@gmail.com on Wed Jul 27 01:57:15 2022
    On Mon, 25 Jul 2022 16:32:57 -0700 (PDT), Phil Allison
    <pallison49@gmail.com> wrote:

    BS Artist ? wrote:

    ==============
    Is there still an engineering Usenet group where the vast majority of
    posts are on topic for electronic design?

    In case there are any electronic engineers still watching this group,
    here is my question:

    ** Thanks for the insults.

    He insulted engineers, not you.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Phil Allison@21:1/5 to jla...@highlandsniptechnology.com on Wed Jul 27 02:39:02 2022
    jla...@highlandsniptechnology.com wrote:
    ================================

    BS Artist ? wrote:

    ==============
    Is there still an engineering Usenet group where the vast majority of
    posts are on topic for electronic design?

    In case there are any electronic engineers still watching this group,
    here is my question:

    ** Thanks for the insults.

    He insulted engineers, not you.


    ** The "BS Artist" troll insulted the entire NG, including YOU.

    JL treats usenet posting as a joke, a self fulfilling belief in his case.


    ..... Phil

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From jlarkin@highlandsniptechnology.com@21:1/5 to pallison49@gmail.com on Wed Jul 27 07:10:00 2022
    On Wed, 27 Jul 2022 02:39:02 -0700 (PDT), Phil Allison
    <pallison49@gmail.com> wrote:

    jla...@highlandsniptechnology.com wrote:
    ================================

    BS Artist ? wrote:

    ==============
    Is there still an engineering Usenet group where the vast majority of
    posts are on topic for electronic design?

    In case there are any electronic engineers still watching this group,
    here is my question:

    ** Thanks for the insults.

    He insulted engineers, not you.


    ** The "BS Artist" troll insulted the entire NG, including YOU.

    JL treats usenet posting as a joke, a self fulfilling belief in his case.


    ..... Phil

    He stated the plain truth: most posts here are dumb and off-topic,
    posted by people obviously unskilled in electronic design.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Jan Panteltje@21:1/5 to Allison on Wed Jul 27 16:07:09 2022
    On a sunny day (Wed, 27 Jul 2022 02:39:02 -0700 (PDT)) it happened Phil
    Allison <pallison49@gmail.com> wrote in <ba1abfe4-a39e-4fe4-9864-06fe4f4bf79cn@googlegroups.com>:

    jla...@highlandsniptechnology.com wrote:
    ================================

    BS Artist ? wrote:

    ==============
    Is there still an engineering Usenet group where the vast majority of
    posts are on topic for electronic design?

    In case there are any electronic engineers still watching this group,
    here is my question:

    ** Thanks for the insults.

    He insulted engineers, not you.


    ** The "BS Artist" troll insulted the entire NG, including YOU.

    JL treats usenet posting as a joke, a self fulfilling belief in his case.


    ..... Phil

    Jo La is just an ego tripper
    his business must run bad with all that time on his hands to post here
    and insult people.

    People like Artist come and go, thought he was an alter-ego of Ph Ho
    to sell his book.

    TIA is not the ony way

    My poppolologies if I am wrong

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Phil Hobbs@21:1/5 to Artist on Wed Jul 27 12:45:28 2022
    Artist wrote:
    On 7/26/22 05:34, Phil Hobbs wrote:
    Artist wrote:
    Is there still an engineering Usenet group where the vast majority of
     posts are on topic for electronic design?

    I'd recommend Guy Macon's moderated group. misc.business.product-dev,
    but it died out 15 or so years back.  (Old inhabitants of SED will
    remember.)

    In case there are any electronic engineers still watching this group,
     here is my question:

    I need to design a TIA of bandwidth up to 5 MHz.

    Is it for a photodiode, or something else?  The usual issue is input
    capacitance.

    <snip>

    It will be a photodiode, currently it is the OSI Optoelectronics InGaAs-120L-FC . This might change. https://www.osioptoelectronics.com/standard-products/ingaas-photodiodes/high-speed-ingaas.aspx


    That's a really small one, about 2 pF. e_N*C noise current will start
    to dominate the Johnson noise current when

    f > sqrt(4 k T / R_F) / (2 pi * e_N * C_in),

    where C_in is the total summing junction capacitance, which includes
    board strays and diode capacitance as well as the amplifier's C_in.

    Some good things to remember:
    1 nV is the 1-Hz voltage noise of 60.4 ohms,
    1 pA is the noise of 16.3k ohms, and
    1 pA is also the shot noise of 3 uA.

    Figuring 10 pF for all the gingerbread you're planning to hang on the
    summing junction, a decent (5 nV) CMOS or JFET amp with a 4k feedback
    resistor will be in the e_N*C region above

    f = 1 pA*sqrt(16.3k / 4k)/(2 pi * 10 pF * 5 nV) = 6.5 MHz.

    Which isn't horrible, but could be better--you'll lose a dB or so of SNR
    at low light.

    However, at 600k ohms, things start falling apart at only 43 kHz, and it
    gets _cubically_ worse above there--since the e_N*C current spectral
    density goes as f, the noise power density goes as f**2, so the integral
    goes as BW**3.


    The currently selected op amp is the LTC6226 https://www.analog.com/en/products/ltc6226.html#product-overview

    Marginally okay at 4k, but not a good choice for higher resistances--its
    input current noise is 2.7 pA in 1 Hz.

    From the rules above, that 2.7 pA equals the shot noise current of

    3 uA * 2.7**2 = 22 uA

    and the Johnson noise current of

    16.3k / 2.7**2 = 2.2k.

    On the other hand, that 1 nV typical noise number helps the e_N*C
    problem a lot--it goes away at 4k, and is 14 dB better at the higher resistances.

    or the TMUX7462F
    https://www.ti.com/lit/ds/symlink/tmux7412f.pdf

    Completely unsuitable--its OFF capacitance is over 10 pF. At 600k ohms,
    you'll have 4k + 10 pF from the SJ either to the output or to ground.

    If it's to the output, it appears in parallel with the 600k, and so will
    reduce the bandwidth to about 25 kHz.

    If it's to ground, that will give you an AC noise gain of 150, besides
    dumping almost the full Johnson noise of the 4k resistor into the
    summing junction. (You'll also need two switches per resistor.)

    Relays are the ticket for that job. Sometimes you can get away with a lower-capacitance MUX such as a TMUX1511.



    I would like to be able to have several gain options for the first stage
    gain from 4K all the way up to 630k. The switch in consideration for
    this is:
    MAX14777.
    https://datasheets.maximintegrated.com/en/ds/MAX14777.pdf
    TMUX7412F
    https://www.ti.com/product/TMUX7412F
    The current idea is to have a high value resistor in the vicinity of
    630k in parallel with the switches, and arrange the switches to switch a choice of one of 4 parallel resistors. The would provide 5 gain options.
    and more if more then one resistor is switched into the feedback path. I
    know having this option will add capacitance to the virtual ground, even though the analog switch would be between the op amp output, and the resistors.

    Sounds like you're going to need to use more than one complete TIA, and
    use relays to switch them in and out. If you're not bootstrapping, you
    can use one TIA at each end of the photodiode, with suitable bias
    arrangements. That does cost some supply headroom, because the PD
    always wants to make the TIA move in the inconvenient direction.


    I am aware of your virtual ground bootstrap techniques for high
    capacitance photodiodes to raise bandwidth, and reduce noise, by
    reducing the capacitance seen by the virtual ground. I do not know right
    now if bootstraping would add more capacitance than would be reduced.

    Sounds like a candidate for what I call a type-2 bootstrap, where the op
    amp's inverting input is driven by the bootstrap output, so that the
    bootstrap is inside the TIA's feedback loop instead of being off to one
    side.

    That gets rid of the op amp's C_in, which is a big win in this instance,
    and allows you to use low-e_N bipolar amps such as the LT6226. It does
    add the JFET's offset and noise voltage, but that's an excellent trade.

    It works much better than the old-fashioned JFET-pair + op amp approach.


    Is the next edition of your book in which you describe bootstrapping out?
    I already have the one before it.

    Yup, it came out in January. Fully revised, and with a whole lot of new material (the LaTeX source is about 37% longer, but some of it is
    commented out in both editions).

    Wiley had to issue it in coffee-table size (8.5x11) to avoid going over
    their mystical 900-page limit. New stuff is now mostly going into the
    new book manuscript, tentatively titled "Designing Electro-Optical
    Systems: 30 Instruments".

    Cheers

    Phil Hobbs

    --
    Dr Philip C D Hobbs
    Principal Consultant
    ElectroOptical Innovations LLC / Hobbs ElectroOptics
    Optics, Electro-optics, Photonics, Analog Electronics
    Briarcliff Manor NY 10510

    http://electrooptical.net
    http://hobbs-eo.com

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  • From John Larkin@21:1/5 to pNaonStpealmtje@yahoo.com on Wed Jul 27 10:17:18 2022
    On Wed, 27 Jul 2022 16:07:09 GMT, Jan Panteltje
    <pNaonStpealmtje@yahoo.com> wrote:

    On a sunny day (Wed, 27 Jul 2022 02:39:02 -0700 (PDT)) it happened Phil >Allison <pallison49@gmail.com> wrote in ><ba1abfe4-a39e-4fe4-9864-06fe4f4bf79cn@googlegroups.com>:

    jla...@highlandsniptechnology.com wrote:
    ================================

    BS Artist ? wrote:

    ==============
    Is there still an engineering Usenet group where the vast majority of >>> >> posts are on topic for electronic design?

    In case there are any electronic engineers still watching this group, >>> >> here is my question:

    ** Thanks for the insults.

    He insulted engineers, not you.


    ** The "BS Artist" troll insulted the entire NG, including YOU.

    JL treats usenet posting as a joke, a self fulfilling belief in his case. >>

    ..... Phil

    Jo La is just an ego tripper
    his business must run bad with all that time on his hands to post here
    and insult people.

    Actually, biz is excellent and trending better.

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  • From Phil Allison@21:1/5 to John Larkin on Wed Jul 27 16:30:12 2022
    John Larkin wrote:
    -------------------------------

    BS Artist ? wrote:

    ==============
    Is there still an engineering Usenet group where the vast majority of >>> >> posts are on topic for electronic design?

    In case there are any electronic engineers still watching this group, >>> >> here is my question:

    ** Thanks for the insults.

    He insulted engineers, not you.


    ** The "BS Artist" troll insulted the entire NG, including YOU.

    JL treats usenet posting as a joke, a self fulfilling belief in his case. >>

    Jo La is just an ego tripper
    his business must run bad with all that time on his hands to post here
    and insult people.

    Actually, biz is excellent and trending better.

    ** Despite JL's presence , not because of it.

    Seem many examples of exactly that, where staff have to conspire to keep their nutty boss at bay.


    ..... Phil

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  • From Phil Hobbs@21:1/5 to Phil Allison on Wed Jul 27 19:53:30 2022
    Phil Allison wrote:
    John Larkin wrote:
    -------------------------------

    BS Artist ? wrote:

    ==============
    Is there still an engineering Usenet group where the vast majority of >>>>>>> posts are on topic for electronic design?

    In case there are any electronic engineers still watching this group, >>>>>>> here is my question:

    ** Thanks for the insults.

    He insulted engineers, not you.


    ** The "BS Artist" troll insulted the entire NG, including YOU.

    JL treats usenet posting as a joke, a self fulfilling belief in his case. >>>>
    >
    Jo La is just an ego tripper
    his business must run bad with all that time on his hands to post here
    and insult people.

    Actually, biz is excellent and trending better.

    ** Despite JL's presence , not because of it.

    Seem many examples of exactly that, where staff have to conspire to keep their nutty boss at bay.


    ..... Phil


    Round SED, of course we have no experience with conspiring to manage
    nutty posters. ;)

    Cheers

    Phil Hobbs

    --
    Dr Philip C D Hobbs
    Principal Consultant
    ElectroOptical Innovations LLC / Hobbs ElectroOptics
    Optics, Electro-optics, Photonics, Analog Electronics
    Briarcliff Manor NY 10510

    http://electrooptical.net
    http://hobbs-eo.com

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  • From John Larkin@21:1/5 to pallison49@gmail.com on Wed Jul 27 17:48:51 2022
    On Wed, 27 Jul 2022 16:30:12 -0700 (PDT), Phil Allison
    <pallison49@gmail.com> wrote:

    John Larkin wrote:
    -------------------------------

    BS Artist ? wrote:

    ==============
    Is there still an engineering Usenet group where the vast majority of >> >>> >> posts are on topic for electronic design?

    In case there are any electronic engineers still watching this group, >> >>> >> here is my question:

    ** Thanks for the insults.

    He insulted engineers, not you.


    ** The "BS Artist" troll insulted the entire NG, including YOU.

    JL treats usenet posting as a joke, a self fulfilling belief in his case. >> >>

    Jo La is just an ego tripper
    his business must run bad with all that time on his hands to post here
    and insult people.

    Actually, biz is excellent and trending better.

    ** Despite JL's presence , not because of it.

    No, really, I have function. Crazy ideas. Inventing things.

    Nowadays, I can't do everything. FPGAs, Linux, Python test set
    software, PCB layout, mechanical design, all that can be mostly
    delegated to saner people.

    "Oh, but it just may be a lunatic you're looking for..."

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  • From Anthony William Sloman@21:1/5 to John Larkin on Wed Jul 27 19:06:37 2022
    On Thursday, July 28, 2022 at 10:49:02 AM UTC+10, John Larkin wrote:
    On Wed, 27 Jul 2022 16:30:12 -0700 (PDT), Phil Allison
    <palli...@gmail.com> wrote:
    John Larkin wrote:
    BS Artist ? wrote:

    <snip>

    JL treats usenet posting as a joke, a self fulfilling belief in his case.


    Jo La is just an ego tripper. His business must run bad with all that time on his hands to post here and insult people.

    Actually, biz is excellent and trending better.

    ** Despite JL's presence , not because of it.

    No, really, I have function. Crazy ideas. Inventing things.

    That's what John Larkin tells himself.

    Nowadays, I can't do everything. FPGAs, Linux, Python test set software, PCB layout, mechanical design, all that can be mostly delegated to saner people.

    Who have had a lot of practice at flattering the boss until he moves on to pester somebody else.

    "Oh, but it just may be a lunatic you're looking for..."

    He can talk to customers for ages, and the more time he spends doing that, the less time he spends distracting people who can still design circuits that work.

    Even the most lunatic idea can be repackaged into something that can be made to work, as long as you can keep the geriatric clown out of the detailed design.

    --
    Bill Sloman, Sydney

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