fast rectifier

[Martin Czech]

Someone on the list asked for rectifier cicuits with fast performance
a while ago. Unity gain compensated op-amp suffer from low slewrate
in such precision rectifier applications where there is no feedback
via the diodes for some time. So the idea is to use op-amps with external
compensation, and "switch of" compensation while the input voltage
crosses the 0 line, the most critical moment. 

http://www.national.com/pf/LM/LM101A.html gives a circuit for this
in LM101A.pdf on page 8.

The circuit should work with most uncompensated op-amps.

m.c.