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Buffers and Caps

Started by Faber, June 16, 2008, 09:50:33 AM

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Faber

Okay, so I have a pedal that's just a buffer -> gain stage.

I was thinking that because the caps between the stages were there to block the DC voltage from crossing into the next stage and that the gain of a buffer (opamp in this case) was unity, would I really need a cap between the stages?

petemoore

  Generally you'll need caps blocking DC between stages to have a DC Bias on each stage.
  There are cases where DC blocking caps arent' used between stages, but that's another thread.
 
Convention creates following, following creates convention.

Faber


Processaurus

Here's some coupling cap discussion, where the drift is that coupling caps are generally the safe way to go, as opamps and such aren't perfect, and errors in the DC output of each stage will likely multiply with gain, and possibly leave things in a misbiased/ asymmetrically clipping state. 

With low gain (especially unity gain buffers) and a limited # of stages, though, you don't need to worry about a coupling cap, and can save the parts.  Try it out!