servo amplifier with current limiter

Discussion in 'General Electronics Chat' started by caluctra, Jan 12, 2012.

  1. caluctra

    Thread Starter New Member

    Oct 27, 2010
    11
    0
    hello all.


    i would like some help if possible in the following:


    I would like to be able to drive a servo valve (coild impedance 300 ohms)


    giving (by me) a +/- 10 v dc signal (from a demodulator ad698) and have

    up to +-.5A of current limit.


    thanks
     
  2. gootee

    Senior Member

    Apr 24, 2007
    447
    50
    For the amplifier, you might want to look at something like an LM1875 or LM675, at national.com . They are just like opamps, as far as the circuit topologies that you can use them in are concerned. But some of them can output up to several amps (or more) of current.

    Some chipamps need a gain of 10 or more to be stable. In that case, just put a resistive voltage divider before the input, if your input signal has a range that is too large.

    You can also use them as a current-booster output stage inside the feedback loops of a Howland Current Pump topology (a type of precision voltage-controlled current source), about which there is a good appnote at national.com. In that case, your current-limiting could be achieved by limiting the input voltage swing.
     
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