I have a piezoelectric sensor that will have a weak AC signal superimposed on a DC signal. The DC signal will be around 5V and the AC signal only mV and with a frequency of 100kHz. Can you recommend a circuit to filter out the DC and to amplify the AC 100 times?

 

hi Agren,
Welcome to AAC.
One option would be using a coupling capacitor, which will block the DC component and allow through the AC component.
Post a sketch of the piezo circuit, we can then suggest solutions.
E

 

Instrumentation Amplifier -

http://www.analog.com/media/en/trai.../designers-guide-instrument-amps-complete.pdf

Representative circuit possibility -

Regards, Dana.