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amplifier

Discussion in 'General Electronics Discussion' started by mahin, Jul 15, 2012.

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  1. mahin

    mahin

    11
    0
    May 2, 2012
    hi everybody,
    i want an amplifier as follow:
    1: signal generator has 600 ohms output impedance and 20v max
    2-power supply=+-60v
    3- load is about 100 ohms
    4- frequency range=<500khz
    5- gain=5,
     
    Last edited: Jul 15, 2012
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,497
    2,839
    Jan 21, 2010
    What's it for?

    Is that gain voltage, or power? Because a voltage gain of 5 with an input signal of 20V RMS will require at least a +/- 150V power supply.
     
  3. mahin

    mahin

    11
    0
    May 2, 2012
    that ia voltage gain, no problem i need 100vp-p at output and input is =<20v(not RMS), if need higher output i think i can change resistors for increase gain .
     
  4. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,497
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    Jan 21, 2010
    What's it for (I ask again)?

    Voltages are normally measured as RMS. The second guess would be peak. If you mean peak to peak, you need to say so.

    You're telling us the peak output voltage is 10V. and you want a peak output voltage of 50V. In that case a +/-60V supply may be OK.

    But what are you driving?

    Voltage gain means that the output voltage is greater (in this case 5 times) more than the input voltage.

    Many amplifiers are not voltage amplifiers. For example if your amplifier was to be used to drive an 8 ohm speaker, it would be a 150W RMS amplifier (approx).

    Now, I can bet that your signal generator probably has an output power measured in milliwatts -- I'll guess it's about 40mW, so the amplifier you want may have a power gain of (a least!) 3700 -- possibly much, much higher.

    And THAT is the reason I need to ask what sort of gain do you want and what is it going to be used for.

    edit: There are other reasons too -- are you concerned with distortion? If so, how much?
     
  5. mahin

    mahin

    11
    0
    May 2, 2012
    i want to stimulate cell within a cuvett and need 20-50vp-p and <2mA current, i have no imformation about load impedance but i guess it is100ohms (i driveed it with an amplifier with 100ohms output impedance then output voltage dropped 50%).
     
  6. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,497
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    Jan 21, 2010
    OK, so a minimum load resistance of 10k -- that makes a huge resistance. We've just gone from a heavy amplifier with a large heatsink to something small enough to stick in your pocket.

    At low currents, the frequency will also be less of an issue I would also imagine that output distortion would not be too much of a concern.

    You will require the +/- 60V for the output drivers, but something less (perhaps +/- 15 for earlier stages of amplification. Do you have access to that too, or will you need to build a regulator?
     
  7. mahin

    mahin

    11
    0
    May 2, 2012
    no problem i can build a regulator,
    have you any offer for this design?if yes plz send me the circuit.
    thank you
     
  8. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,497
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    Jan 21, 2010
    Sorry, I've let you go unanswered for a while.

    You may be able to get away with a high frequency op-amp driving a class B output.

    The op-amp will need to run off (say) +/- 15V rails and the output transistors from the higher voltage rail (clearly 0V will be common).

    You'll need transistors capable of withstanding about 150V, but they're not going to be dissipating too much power. They should be inside the op-amp's feedback loop.

    Figure 4 here is kinda the idea, except the transistors they specify are not acceptable at the frequencies you want and the collectors are not taken to a higher voltage rail.
     
  9. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

    4,960
    652
    May 8, 2012
    Google the PA240 High Voltage OpAmp data sheet and see if it meets your requirements.
     
  10. Miguel Lopez

    Miguel Lopez

    252
    63
    Jan 25, 2012
    Up to 500kHz? Living cells? What kind of cells are you going to stimulate. Sorry, for the question, I work on a biopharmaceutical factory and I'm curious.
     
  11. mahin

    mahin

    11
    0
    May 2, 2012
    i wnt to use MCF-7 cell line,
     
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