Figure 7.3. There is an AC generator on the left. One side is grounded and the other side connects through a 0.01 u f cap to the noninverting input of an op amp. There is a 10 meg ohm resistor connected from the noninverting input to ground. Although this resistor has no number it is presumed that it is R1. The output of the op amp connects through a 100 pf cap to the inverting input. The output also connects to two diodes, to the cathode of one and the anode of the other. The free end cathode of one diode connects to the cathode of a third diode. The free end anode connects to the anode of a fourth diode. The free end anode and free end cathode of the third and fourth diodes connect together and go to ground through a resistor labeled R2. The ungrounded end of R2 also goes to the inverting input of the op amp. The point where the two diode cathodes connect goes to one side of a milliammeter. The point where the two diode anodes connect goes to the other side of the milliammeter. End verbal description.
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