"High" Voltage Mosfet Amp

Discussion in 'Electronic Design' started by Jeff Johnson, Jan 11, 2011.

  1. Jeff Johnson

    Jeff Johnson Guest

    I have some

    http://www.fairchildsemi.com/ds/FQ/FQN1N60C.pdf

    and would like to make a simple mosfet audio voltage amplifier(common
    source). Possibly using drain feedback bias and/or source degeneration. The
    power supply is around 500V. Is there any difference I should be worried
    about from a similar low voltage case? I'm looking for a gain of around 20
    with an input swing of about 1V max.
     
    Jeff Johnson, Jan 11, 2011
    #1
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  2. Jeff Johnson

    Jeff Johnson Guest

    "George Herold" <> wrote in message
    news:...
    > On Jan 10, 8:41 pm, "Jeff Johnson" <> wrote:
    >> I have some
    >>
    >> http://www.fairchildsemi.com/ds/FQ/FQN1N60C.pdf
    >>
    >> and would like to make a simple mosfet audio voltage amplifier(common
    >> source). Possibly using drain feedback bias and/or source degeneration.
    >> The
    >> power supply is around 500V. Is there any difference I should be worried
    >> about from a similar low voltage case? I'm looking for a gain of around
    >> 20
    >> with an input swing of about 1V max.

    >
    > I'm confused, the supply is 500V, and the input is 1V with a gain of
    > 20?
    > Sounds like you need more gain.
    > Can you post a pic of a schematic?
    > What are you driving?
    >


    Sure I would like more than a gain of 20. 100 Ideally. If I use drain
    feedback bias there is no way to get past 30 since this would easily put me
    over the max V_GS of 30V.
     
    Jeff Johnson, Jan 11, 2011
    #2
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  3. Jeff Johnson

    Phil Allison Guest

    "Jeff Johnson"

    > Sure I would like more than a gain of 20. 100 Ideally. If I use drain
    > feedback bias there is no way to get past 30 since this would easily put
    > me over the max V_GS of 30V.



    ** That would be funny if he was not serious.



    ...... Phil
     
    Phil Allison, Jan 11, 2011
    #3
  4. Jeff Johnson

    Guest

    On Mon, 10 Jan 2011 19:41:14 -0600, "Jeff Johnson"
    <> wrote:

    >I have some
    >
    >http://www.fairchildsemi.com/ds/FQ/FQN1N60C.pdf
    >
    >and would like to make a simple mosfet audio voltage amplifier(common
    >source). Possibly using drain feedback bias and/or source degeneration. The
    >power supply is around 500V. Is there any difference I should be worried
    >about from a similar low voltage case? I'm looking for a gain of around 20
    >with an input swing of about 1V max.


    Are you trying to reinvent the Fetron, a high voltage FET with the
    same pinout as some well known triodes ?
     
    , Jan 11, 2011
    #4
  5. Jeff Johnson

    Phil Allison Guest

    <>
    >
    > Are you trying to reinvent the Fetron, a high voltage FET with the
    > same pinout as some well known triodes ?



    * Nope, the wanker trying to re-invent the wheel.

    He wants to make a square version.

    BTW:

    Fetrons used high voltage j-fets in a metal pack that typically simulated a
    9 pin dual triode.



    ...... Phil
     
    Phil Allison, Jan 11, 2011
    #5
  6. Jeff Johnson

    Phil Allison Guest

    "Bill Slowman is a Dope"


    He's probably trying to drive an electrostatic speaker.

    ** ROTFLMAO !!

    Da Slow Man is an utter IDIOT !!



    Back in the 1960's there were a bunch of articles about building your
    own electrostatic speakers, and the high voltage amplifiers to drive
    them. Quad just used step-up transformers, which made a load that many
    audio-amplifiers didn't like driving.


    ** Bollocks.

    The original Quad ESL 57 could be driven satisfactorily by any good audio
    amplifier that was stable and able to drive a 16 ohm load.

    The later (1982) Quad ESL63 had a very benign impedance characteristic that
    any hi-fi amp worthy of the name could drive easily up to full output at any
    audio frequency.

    Facts baffle bullshitters.



    ..... Phil
     
    Phil Allison, Jan 11, 2011
    #6
  7. Jeff Johnson

    Jeff Johnson Guest

    <> wrote in message
    news:...
    > On Mon, 10 Jan 2011 19:41:14 -0600, "Jeff Johnson"
    > <> wrote:
    >
    >>I have some
    >>
    >>http://www.fairchildsemi.com/ds/FQ/FQN1N60C.pdf
    >>
    >>and would like to make a simple mosfet audio voltage amplifier(common
    >>source). Possibly using drain feedback bias and/or source degeneration.
    >>The
    >>power supply is around 500V. Is there any difference I should be worried
    >>about from a similar low voltage case? I'm looking for a gain of around 20
    >>with an input swing of about 1V max.

    >
    > Are you trying to reinvent the Fetron, a high voltage FET with the
    > same pinout as some well known triodes ?


    Possibly...
     
    Jeff Johnson, Jan 11, 2011
    #7
  8. Jeff Johnson

    Jeff Johnson Guest

    <> wrote in message
    news:...
    > On Jan 10, 5:41 pm, "Jeff Johnson" <> wrote:
    >> I have some
    >>
    >> http://www.fairchildsemi.com/ds/FQ/FQN1N60C.pdf
    >>
    >> and would like to make a simple mosfet audio voltage amplifier(common
    >> source). Possibly using drain feedback bias and/or source degeneration.
    >> The
    >> power supply is around 500V. Is there any difference I should be worried
    >> about from a similar low voltage case? I'm looking for a gain of around
    >> 20
    >> with an input swing of about 1V max.

    >
    > You're not expect linearity with DMOS I hope. You might want to see
    > who is left making fets with lateral current flow.


    Well, I don't mind a little bit of non-linearity... The datasheet shows it
    might be pretty bad though ;/
     
    Jeff Johnson, Jan 11, 2011
    #8
  9. Jeff Johnson

    Jon Kirwan Guest

    On Tue, 11 Jan 2011 06:28:16 -0800 (PST), Bill Sloman
    <> wrote:

    ><snip>
    >Go argue with the late W. Ralph Knowles.
    >
    >http://www.oregonlive.com/obituaries/oregonian/index.ssf?/base/obits/121417890693840.xml&coll=7
    >
    >He was anything but an idiot - quite a lot smarter than most of the
    >people in his line of work, Which is why he ended up as director of
    >research and development for North America for FEI Co.
    ><snip>


    Interesting. I worked at FEI for a while and then afterwards
    helped develop a product, self-employed, to help extend the
    average life expectancy of their electron emitters hidden
    behind the wehnelt.

    Jon
     
    Jon Kirwan, Jan 11, 2011
    #9
  10. Jeff Johnson

    Jon Kirwan Guest

    On Tue, 11 Jan 2011 12:27:02 -0800 (PST), Bill Sloman
    <> wrote:

    >On Jan 11, 6:39 pm, Jon Kirwan <> wrote:
    >> On Tue, 11 Jan 2011 06:28:16 -0800 (PST), Bill Sloman
    >>
    >> <> wrote:
    >> ><snip>
    >> >Go argue with the late W. Ralph Knowles.

    >>
    >> >http://www.oregonlive.com/obituaries/oregonian/index.ssf?/base/obits/...

    >>
    >> >He was anything but an idiot - quite a lot smarter than most of the
    >> >people in his line of work, Which is why he ended up as director of
    >> >research and development for North America for FEI Co.
    >> ><snip>

    >>
    >> Interesting.  I worked at FEI for a while and then afterwards
    >> helped develop a product, self-employed, to help extend the
    >> average life expectancy of their electron emitters hidden
    >> behind the wehnelt.

    >
    >Presumably by controlling the heat dissipated in getting the electron
    >emitter up to the temperature where it would emit electrons.
    >
    >IIRR - and I was never directly involved with that part of the
    >electron microscope - that wasn't normally directly controlled. The
    >circuit would be floating at an anything up to -30kV, which would make
    >it more than a little interesting.


    Lower temperatures produce far too few electrons (as you
    already know very well, the electrons are produced both from
    thermal emission _and_ field effect), lessens the beam
    intensity, and reduces the rate at which work can get done
    (beam sweeping rate.) Which impacts productivity. By quite
    a lot with even small changes. Higher temperatures works
    great for beam intensity, but quickly destroys the emitter.
    (Which is also treated with Lanthanum hexaboride, memory
    serving.) The trick is to accurately temperature over time
    without drift. And we are talking on the order of tenths of
    a Kelvin to perhaps one Kelvin, where possible. Now think
    about the local (dI/I)/(dT/T) problem at those temperatures
    T, if done pyrometrically, even assuming emissivity doesn't
    change over time.

    Early solutions were to use inordinately expensive current
    drive power supplies (better than 0.1%.) They may drift a
    little and need recalibration but that's less important
    because the tips themselves age faster still. But the
    reality is that the temperature at the tip is the thing to be
    controlled, not the current driving it. The tip temperature
    needs to be closed up within the control loop. Periodic
    adjustment using disappearing filament methods and calibrated
    (expensive) tungsten standards achieves bringing temperature
    into the loop, if done manually and frequently. The problem
    is... well, all the problem in doing that. It means other
    specialized power supplies for the standard lamp, careful
    logging of lamp usage and recalibration as needed, regular
    procedures done frequently, etc.

    Variations in lifetime might be as much as a factor of 50X
    for the exact same system, depending on customer procedures.
    And at the high expense of replacement, it becomes urgent to
    find an easier way to achieve more uniform experiences.

    Jon
     
    Jon Kirwan, Jan 11, 2011
    #10
  11. Jeff Johnson

    Phil Allison Guest

    "Bill Slowman is a Fucking Dope"
    >
    > He's probably trying to drive an electrostatic speaker.
    >
    > ** ROTFLMAO !!


    You disagrre with the propositon that the OP might be trying to drive
    an electrostatic speaker?

    ** Errr - yes.


    > Da Slow Man is an utter IDIOT !!


    Not actually true.

    ** Fraid its is - you fucking fuckwit.


    > Back in the 1960's there were a bunch of articles about building your
    > own electrostatic speakers, and the high voltage amplifiers to drive
    > them. Quad just used step-up transformers, which made a load that many
    > audio-amplifiers didn't like driving.
    >
    > ** Bollocks.
    >
    > The original Quad ESL 57 could be driven satisfactorily by any good audio
    > amplifier that was stable and able to drive a 16 ohm load.


    Go argue with the late W. Ralph Knowles.

    ** How absurd.

    Go **** yourself - you pathetic old twat.


    > The later (1982) Quad ESL63 had a very benign impedance characteristic
    > that
    > any hi-fi amp worthy of the name could drive easily up to full output at
    > any
    > audio frequency.
    >
    > Facts baffle bullshitters.


    I wasn't talking about the Quad ESL63 - I was working for Ralph
    Knowles in the early 1980's, when he was worrying about driving his
    ESL 57, which he'd had for years.


    ** Read the fucking post - shit head.


    None of the facts you've adduced contradict anything I wrote,


    ** Shame how you have been utterly contradicted.

    > and none of what I've written is bullshit.



    ** All of it was.

    All you did was present myths as fact.

    Cos you don't have anything better.



    ...... Phil
     
    Phil Allison, Jan 12, 2011
    #11
  12. Jeff Johnson

    Phil Allison Guest

    Re: "High" Voltage Mosfet Amp - Quad ESL63

    "Bill Sloman is so Full of Bullshit "


    > Back in the 1960's there were a bunch of articles about building your
    > own electrostatic speakers, and the high voltage amplifiers to drive
    > them. Quad just used step-up transformers, which made a load that many
    > audio-amplifiers didn't like driving.
    >
    > ** Bollocks.
    >
    > The original Quad ESL 57 could be driven satisfactorily by any good audio
    > amplifier that was stable and able to drive a 16 ohm load.
    >
    > The later (1982) Quad ESL63 had a very benign impedance characteristic
    > that
    > any hi-fi amp worthy of the name could drive easily up to full output at
    > any
    > audio frequency.


    The Quad ESL63 had rather more than a transformer to drive the
    electrostatic moving parts

    http://www.stereophile.com/floorloudspeakers/416


    ** Yeah, yeah - I know all that.

    Got nothing to do with you mad assertions re the ESL57.

    FYI:

    The impedance presented to an amplifier by the ESL57 is at or above 8 ohms
    from 25Hz to 7kHz - which easily covers the entire power band in recorded
    music.

    From 50 Hz to 5 kHz, the impedance is 15 ohms or higher.

    Any hi-fi audio amp (valve or SS) worth the title can drive such a load with
    recorded music signals.

    You have no case.

    **** off.


    ...... Phil
     
    Phil Allison, Jan 12, 2011
    #12
  13. Jeff Johnson

    Jon Kirwan Guest

    On Tue, 11 Jan 2011 15:24:46 -0800 (PST), Bill Sloman
    <> wrote:

    ><snip of discussion about LaB6 crystal>


    It was sputtered material on tungsten, not a crystal. It's
    possible I remember wrong about the material, though.

    Jon
     
    Jon Kirwan, Jan 12, 2011
    #13
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