Talk:Charge amplifier

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[edit] Input impedance

From the article:

A piezoelectric transducer has very high DC output impedance and appears as a voltage source in series
with a capacitor. A charge amplifier therefore needs to have a very high input impedance at DC.

I removed the whole paragraph, as this is wrong and borderline meaningless. It would have made sense if we were speaking of a voltage amplifier. The charge amplifier provides a signal proportional to the charge it has taken from the input. For this reason, it's better to see the piezo source as a current source with a shunt capacitor. To read current, we need a low input resistance, which is provided by the OA. —Preceding unsigned comment added by 128.141.87.240 (talk) 14:01, 10 March 2008 (UTC)