OP90 Single Op Amp Full-Wave Rectifier
A full-wave rectifier circuit that provides the absolute value of input signals up to ±2.5 V even though operated from a single 5 V supply is shown in the schematic diagram below.
The amplifier acts as a unity-gain inverter for negative inputs. The op amp output is forced by positive signal to ground. The 1N914 diode becomes reversed-biased and the signal passes through R1 and R2 to the output. Load impedance cause an asymmetric output since output impedance is dependent on input polarity. This can be corrected by reducing R2 for constant load impedance. A second OP90 can buffer varying or heavy loads. The output of the full-wave rectifier with a 4 Vp-p, 10 Hz input signal also shown in figure below. [Circuit’s schematic diagram source: analog.com]