an op amp and ic based Full wave rectifier

This circuit acts rectifier the ACV signal.This circuit usually requires two op-amp, but this circuit uses only one op-amp.
The work is easy when a positive input into, The D1, D2 will does not work. The output is equal to R2 / (R2 + R3).When V1 is the input signal and R2 = R3 = R, we will have the output signal V0 = 1 / 2 V1.
Later, when the negative output signal into. The D2 to conduct, but D1 does not work. When this circuit is the inverting circuit, output has values V0 = R2/R1 V1, where R1 = 2R, and R2 = R, so V0 = 0.5 V1.
This piece was positive, but the same direction, so the output out.

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