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Help for a piezoelectric transducer amplification

Other Parts Discussed in Thread: INA125, TL082, TLC251, OPA353, LM335, LMC660

Hi,

I need an opamp to amplify the signal from a piezoelectric transducer (piezoelectric disc - 35mm), and I noticed in your document “AN-31 Op Amp Circuit Collection” that you have a circuit for a piezoelectric transducer with an opamp that is now discontinued ( LM108 )… So I started looking for others, and I found INA125, TLC251, TL082, LMC660, LM335, OPA353 – which one would you recommend, or are there other better solutions?  

Another doubt I have is that after pre-amplifying the piezo, it will be connected to a sound card (http://www.roland.com/products/en/UA-25/) having a maximum Nominal Input Level of +4 dBu. I’ve searched about how to convert dBu for mV, in order to know the maximum I can amplify with the opamp, and I realized that +4 dBu = 1,23V = 1230mV. My problem is that I don’t know the maximum mV of the sensor, so that I can calculate its gain. How could I solve this issue?

I have one last question… I gathered these data from the sensor: Resonant Frequency: 2.6KHz ±0.3KHz; Resonant Impedance: 250R; Capacitance: 400nF. Are they relevant for the opamp choice?

thanks,

Carlos Esteves

  • Hi, Carlos,

    There are lots of different variables in play here, I think your best bet is to just bread board up something and start playing with it to see what the output level of your transducer is so you can determine the gain, etc, etc.

    Keep an eye out for oscillations. The capacitive load of the piezo on the input of the op amp might cause problems.

    -d2