precision rectifier

[Martin Czech]

You don't need two op amps.  The normal signal is feed through (resistor).
A HWR will invert and amplify 2x.  Add all in a passive network. During
positive excursions the HWR is shut, thus normal signal.  In negative
the HWR will outperform the direct path so the result has also unity
amplitude.

The three resistor network will add things up, since
it is passive you will have some amplitude missing,
but the rectification is precise.

Works if not exactly unity gain or even larger then unity
gain is needed and input/output impedance is stable and known.
This is true for most if not all applications I can think of.

m.c.