Charge-Sensitivity in Preamplifier

[dlbi]

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...

 

[Mike_In_Plano]

Are you designing this amplifier, or attempting to reverse engineer someone else's equipment?

 

[dlbi]

Are you designing this amplifier, or attempting to reverse engineer someone else's equipment?

I am characterizing a preamp in my lab.

 

[Mike_In_Plano]

Your measurements have accurately described a charge amplifier.

 

[dlbi]

Your measurements have accurately described a charge amplifier.

Thank you! By can you explain to me why? I figured it was charge sensitive, but I'm having a hard time grasping why.

 

[Mike_In_Plano]

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.