fast rectifier

[Don Tillman]

   From: Martin Czech <martin.czech at itt-sc.de>
   Date: Wed, 6 Aug 1997 08:16:31 +0200 (MET DST)

   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. 

I like the single transistor Moog circuit a lot better; it doesn't
suffer from glitchy behavior due to slewing.

This is the circuit that is used on the VCOs to generate a triangle
wave from a sawtooth -- it's a single common-emmiter transistor biased
so that it runs inverting for half a cycle and the base-collector
junction conducts and it runs non-inverting for the other half a
cycle.

  -- Don
		"Let me know the rESULTS ,I'M INTO INDUSTRIAL NIGHTMARE !!!."
		  -- Oscar <storm at redestb.es>, AH, 27 May 97