[sdiy] 3 position switch help

[Dave Manley]

As a variation on the theme - here's an interesting single supply, full 
wave rectifier without *any* diodes.  Requires rail-rail op-amps.

http://www.edn.com/index.asp?layout=article&articleid=CA6250014

-Dave

Grant Richter wrote:
> Put two diodes inside the feedback loop of two op-amps. One for 
> positive, one for negative.
> Then you have two precision halfwave rectifiers.
> 
> Invert the output of one, and sum it with the other for full wave 
> rectification.
> A quad op-amp would do the whole thing. And all the waveforms are 
> available at the same time.
> 
> On May 19, 2008, at 8:16 PM, Paul Perry wrote:
> 
>> Very familiar indeed.
>> That circuit makes me wonder though - is there a fairly elegant way to 
>> make
>> a three output peak rectifier (pos, neg, and full) so that instead of
>> switching, you have the three options continuously available?
>>
>> paul perry Melbourne Australia
>>
>> -----Original Message from Dave Manley-----
>>> Well lookie here at the fourth Google hit when searching "C&K 7211":
>>> http://www.edn.com/article/CA6339250.html
>>> The author looks familiar.  :-)