The usual waveform of alternating current in most electric power circuits is a sine wave, whose positive half-period corresponds with the positive direction of the current and vice versa. So, is it possible to change the waveform to the modulus of a sine wave? And if so, with what?
This circuit is called a dropless full-wave rectifier, absolute-value circuit or super-diode. The function of it is to perform full-wave rectification without the diode drops that occur in a "normal" full-wave rectifier.
When the input swings negative, the anode of D2 remains at 0 V and IC2 performs unity gain inversion. When the input swings positive, IC1 acts as a unity gain inverter and because of the weightings of IC2's input resistors, twice the negative value of Vin is added to Vin and inverted by IC2 to produce an output equal to Vin.