MOTM

Either a half or full-wave rectifier will do it.  For a half-wave 
rectifier circuit, look at the CV processing circuit on Ken Stone's 
Voltage Controlled Divider:

http://www.cgs.synth.net/

A half-wave rectifier will simply cut off the negative voltages, but 
allow all positive voltages to pass through with as much accuracy as the 
resistors in the circuit allow.  The rectifier circuit uses one TL072 op 
amp (both sections).  A full-wave version is also doable with one dual 
op amp.  The full-wave will invert any negative voltages and make them 
positive.  Use whichever circuit meets the need.  See Electronotes for 
FW rectifier circuits.

-Richard Brewster

Jeffrey Pontius wrote:

>To the experts (which is most everyone here but me),
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>I working with a small circuit that I would like to add voltage control
>(e.g., lfo, env.) through an attenuating pot.  When negative voltages
>(e.g., from an lfo waveform) enter the circuit they 'screw things up'.  Is
>there a "simple" way to restrict the incoming voltages to positive
>voltages only?
>
>Thanks, Jeff
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>Yahoo! Groups Links
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