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Charge-Sensitivity in Preamplifier

  1. Feb 22, 2015 #1
    How I tell if a preamplifier is charge sensitive? I have data taken from a preamplifier that is fed a pulse from a voltage pulser that is fed through a current generator.

    As the pulse voltage was increased the preamp output voltage increased linearly. As the pulse width was increase the preamp output voltage increase linearly also.

    What should I make of this?

    Also how to I determine the time constant of this preamp? The output voltage of my preamplifier does not appear to decay over time... there is a very sharp dip after the preamplifier's maximum output voltage, but I figure that is just some artifact of some sort...
  2. jcsd
  3. Feb 22, 2015 #2
    Are you designing this amplifier, or attempting to reverse engineer someone else's equipment?
  4. Feb 22, 2015 #3
    I am characterizing a preamp in my lab.
  5. Feb 22, 2015 #4
    Your measurements have accurately described a charge amplifier.
  6. Feb 22, 2015 #5
    Thank you! By can you explain to me why? I figured it was charge sensitive, but I'm having a hard time grasping why.
  7. Feb 22, 2015 #6
    I don't know if the expression "charge sensitive" is a very good description because most any amplifier will react to introduction of charge.

    The charge amplifier is unique in that the output indicates the accumulated amount of charge (i.e. current x time) that has been injected over a prolonged time.
    Other amplifiers typically react to a charge injection and then quickly settle back to zero.

    So, a charge amplifier is an integrator.

    It is effective at indicating the number of charged particles that have been accumulated on a surface, the number of photons / ionizations that release charged particles in detectors, or conditioning the signal from charge-displacement sensors (such as a quartz accelerometer)

    The charge amplifier may be self-resetting (i.e. slowly settling back to zero), or externally reset via a signal commanding it to reset to zero.
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