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Piezo flexture precision positioning system
This circuit uses an OP77 to form a piezo flexture element precision positioning system. The high gain and low offset voltage of the OP77 produce an accurate, stable drive voltage to the piezo device allowing predictable, repeatable sub-micron movements to be easily controlled. The output of the OP77 creates a proportional current drive through the common-base connected Q1 to the base of Q3. Q3 forms a Class A amplifier with bias resistor R5, and the transistor Q2 is simply an emitter-follower used for output current boost. R6 is necessary to prevent oscillation caused by the capacitive loading of the piezo device on the output of the amplifier. Note that C1 and C2 are 1kV ceramic type. In this circuit Av=-R2/R1. CAUTION...THIS CIRCUIT USES DANGEROUS VOLTAGES...BE CAREFUL!