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Piezoelectric transducer amplifier
This circuit uses an OP-41 to form an amplifier for piezoelectric transducer. It can be used for high-impedance AC transducers like a piezoelectric accelerometer. These sensors normally require a high input resistance amplifier. The OP-41 can provide input resistances in the range of 10,000,000 megohms, however a dc return for bias current is needed. To maintain a high Rin, large value resistors above 22 megohms are often required. These may not be practical. Using this circuit, input resistances that are orders of magnitude greater than the values of the dc return resistors can be obtained. This is accomplished by bootstrapping the resistors to the output. The lower cutoff frequency is approximately R1*C1.