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+/-33V outputs - What opamp could I use?

Discussion in 'General Electronics Chat' started by atferrari, Feb 11, 2012.

  1. atferrari

    atferrari Well-Known Member

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    I wonder if is it possible to do something similar to what is proposed here

    http://www.electro-tech-online.com/threads/pwm-signal-to-lm317-to-adjust-voltage-output.125091/

    but this time to get two control signals: one from 0 to +33V to control an LM317 and another from 0 to -33V to control an LM337.

    I imagine two separate opamps, one powered between 0 and +38V and the other between -38V and 0V. (I have those +/-38V DC available from an old power supply).

    What could be the most suitable opamps?

    Searching through Farnell I can at least compare some but the prices of the suitable(?) ones is scary. To come to my hands I have to think of them multiplied around 4 times!!

    Maybe I am overlooking something...

    Any suggestions? Gracias
  2. MrAl

    MrAl Well-Known Member Most Helpful Member

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    Hi,


    You think you could post a schematic rather than have us search through a bunch of posts to see what you actually want to do? I think this would help a lot for people reading this thread. I know it would help me to understand you better.
  3. alec_t

    alec_t Well-Known Member Most Helpful Member

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    If I understand you correctly you want one PWM signal to give two simultaneous outputs; one of them negative (0 to -33) and the other positive (0 to 33) ?
  4. atferrari

    atferrari Well-Known Member

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  5. alec_t

    alec_t Well-Known Member Most Helpful Member

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    The op-amps themselves aren't critical as they don't have to withstand 33V. You could run them at, say, 12V and use them to drive BJTs or FETs switching loads operating from 33V.
    Last edited: Feb 11, 2012
  6. ronsimpson

    ronsimpson Well-Known Member Most Helpful Member

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    ONLINE

    High voltage op amps are not so common but:
    AD8274
    ADA4004
    LTC6104, LTC6103, LT1013
    AD5749
    OP4177
    PA340CC
    PA341CE
  7. alec_t

    alec_t Well-Known Member Most Helpful Member

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    Perhaps this? Almost any opamp (I used a LM324 model) with rail to rail input will do. Not having a LM317 or LM337 model I used LT1085 and LT3015 respectively. There are two 0V to +5V PWM inputs (from a micro). One opamp has a 5V supply, the other a -5V supply. The regulators have +33V and -33V supplies respectively.
  8. atferrari

    atferrari Well-Known Member

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    Will try it.

    Busy with vessels right now but I will try it.

    Gracias.

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