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Part Number: TL082
I'm in a development phase of a project in which I need to amplify the received output from a piezo element(ultrasonic). I am getting the raw output(without amplification) ~40mVp-p. The excitation of the transmitter piezo is 200kHz, 12Vp-p square wave.
I am testing with TL082 dual opamp for the amplification of this signal. Since the limitation of the GBWP of 8MHz[Edit: 3MHz], I am using two stage amplification with a gain of 15(both stages).
Supply voltage is 12V. When I turn on the power supply, the amplified signal looks good, but after some time(~5 mins) the amplified signal goes off and seems like the raw signal. If I restarts the power supply, the amplified signal becomes good again.
Question No.1 - What could be the problem behind this strange behavior?
The circuit is given below,
Input and output waveforms are,
Question No. 2 - Will it be better to use opamp with higher GBWP like OPA365, in which I can use opamp in higher gain like 100?
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If the gain drops a little then bandwidth change in the TL082 is responsible.
If the gain drops a lot, then check the DC bias on the TL082 pins as there may be a bad connection in the circuit.
Kai is right that you need a higher bandwidth device.
Regards,Ronald MichallickLinear Applications
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