Circuit Diagram Knowledge

An absolute value circuit, using the CA313O is shown. During positive excursions, the input signal is fed through the feedback network directly to the output.
Simultaneously, the positive excursion of the input signal also drives the output terminal (No. 6) of the inverting amplifier negative such that the 1N914 diode effectively disconnects the amplifier from the signal path. During the negative going excursion of the input signal, the CA313O functions as a normal inverting amplifier with a gain equal to R2/R1. When the equality of the two equations shown is satisfied, the full-wave output is symmetrical. 

Peak-detector circuits are easily implemented with the CA3130, as illust- rated. lt should be noted that with large-signal inputs, the bandwidth of the peak-negative circuit is much less than that of the peak-positive circuit. The second stage of the CA313O limits the bandwidth in this case.