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    high voltage amplifier

    Hello.
    I need to build some strange amplifier:
    input range +-10V
    output +- 3kV
    BW DC..few kHz
    Its output should be able to sink/source current approx. of few mA.
    Can anyone give me some directions on output stage?
    Or maybe some useful links?

    Thank you for reply.

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    high voltage amplifier schematics

    what is the supply for this beast? Not sure if transistors can handle this voltage, even if you stack them. May be use vacuum tubes.



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    Re: High Voltage Amplifier

    You will have to use transistors rated at 7 kV. One method is to use two current mirrors facing each other across the output connection. One from the + supply and one from the - supply. These mirrors are driven from variable current sources referenced to ground. This makes their input voltage range within the +-15V output capability of op amps. Then sense the output voltage through a resistor (that is rated at 7 kV) and use an inverting op amp circuit with the inputs diode clamped to the +-15V supply to protect the op amp.



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    Re: High Voltage Amplifier

    Thank you.
    Quote Originally Posted by sutapanaki
    what is the supply for this beast?
    Supply is not a problem, I'll use some multiplier or HF DC/DC transformer.
    Quote Originally Posted by sutapanaki
    Not sure if transistors can handle this voltage, even if you stack them. May be use vacuum tubes.
    I was looking for HV transistors, and easy available are max. about 1000V.
    With RF power tubes it probably can be done, but I can't use tubes:(
    Quote Originally Posted by flatulent
    You will have to use transistors rated at 7 kV
    I'd love to use them, but were to find it?:)
    Quote Originally Posted by flatulent
    One method is to use two current mirrors facing each other across the output connection. One from the + supply and one from the - supply. These mirrors are driven from variable current sources referenced to ground. This makes their input voltage range within the +-15V output capability of op amps. Then sense the output voltage through a resistor (that is rated at 7 kV) and use an inverting op amp circuit with the inputs diode clamped to the +-15V supply to protect the op amp.
    Thank you very much.
    How about serial connected transistors rated for 1KV ( they are easy available ). Probably there will be a problem with 'dynamic voltage dividing' ( transistors will have slightly different parameters )
    And one more question:
    -is it ok to make supply ( DC/DC converter running at say about 1 MHz) which is tracking input signal, to provide dynamic supply (+-)?



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    Re: High Voltage Amplifier

    It is possible to stack up the transistors and equalize their Vce by using the classical method of putting their bases to taps on a voltage divider.

    This method goes back to the early days of transistor power audio amplifiers.



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    Re: High Voltage Amplifier

    Thanks again:)
    Can you, please, point me to some sites?



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    Re: High Voltage Amplifier

    After saying all of the above, there are some serious safety and legal issues to face. Parts have to be special high voltage rated and the construction practices have some restrictions. If you are not supervised by someone with high voltage experience you should not risk the safety of your self and your customers. Not getting the income from the job is well worth the absence of killing yourself or your customer with the resulting legal actions.

    One further thing is that the feedback resistor should be a divider reducing the 7 kV to 15 V so that there is absolutely no danger of damaging the op amp. You will have to use special test probes as well.

    http://www.pwrx.com/pages/newsflash/...p?file=270.htm
    also try zetex and supertex companies. Zetex makes 500 V bipolars and supertex makes 500 V MOS.

    You might try talking with people in the physics department at a near by university for device suggestions.



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    Re: High Voltage Amplifier

    Quote Originally Posted by flatulent
    Not getting the income from the job is well worth the absence of killing yourself or your customer with the resulting legal actions.
    I promis not kill anyone using this amp:)

    Thanks again.

    Anyone have some more suggestions...?



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