Piezoelectric sensor preamplifier

I have a piezo sensor providing me a 1mV voltage signal on a 1Mohm input impedance measurement instrument. I need to build an amplifier which can return an output voltage of about 1V.

Which do you think would be the best solution: a 2 stage voltage amp: a voltage follower and an inverter, capacitively coupled or a transimpedance amplifier.

To me, it seems the voltage amplifier solution is the best. For a 1mHz to 40 Hz bandwidth which op amp would be most appropriate; what do you think about OP07?

Thanks in advance!

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  • Straight forward voltage amplification seems the obvious choice unless there are constraints you haven't mentioned. You are looking for a gain of 1000 at 40Hz, so a single stage amplifier can do the job provided it has a GBW of at least 400kHz. If you really need to go down to 1 mHz, then you will be looking at DC coupling, and you will need a really low offset and low drift amplifier. After all, a 10uV offset is 1% of your signal. I would ignore anything as old as the OP07 (excellent in its day) and look at the ADA4528 or AD8571.

    PS don't forget to add input protection as piezos can generate big voltages if you knock them

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  • Straight forward voltage amplification seems the obvious choice unless there are constraints you haven't mentioned. You are looking for a gain of 1000 at 40Hz, so a single stage amplifier can do the job provided it has a GBW of at least 400kHz. If you really need to go down to 1 mHz, then you will be looking at DC coupling, and you will need a really low offset and low drift amplifier. After all, a 10uV offset is 1% of your signal. I would ignore anything as old as the OP07 (excellent in its day) and look at the ADA4528 or AD8571.

    PS don't forget to add input protection as piezos can generate big voltages if you knock them

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