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Basic_piezo_ceramic_based_filter

2017-02-23 12:08  
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Basic_piezo_ceramic_based_filter
This circuit is a highly selective bandpass filter that uses a resonant ceramic element and a single amplifier. The ceramic element looks like a high impedance off the resonant frequency (400 kHz, in this case). At resonance, the ceramic element has a low impedance, and A1 responds as an inverter with gain. As shown, the ceramic element has stray or parasitic capacitance that causes a slight rise in output at frequencies above 425 kHz. Typically, the A1 output is down about 20 dB at 300 kHz and 40 dB at 425 kHz. The parasitic capacitance can be minimized with a differential network (Fig. 7-11). Linear Technology Corporation, 1991, AN47-48.