[sdiy] DC Offset Injector?

[Tim Parkhurst]

> -----Original Message-----
> From: Peter Grenader [mailto:peter at buzzclick-music.com]
> Sent: Wednesday, March 17, 2004 4:53 PM
> To: Oren Leavitt; synth-diy at dropmix.xs4all.nl
> Subject: Re: [sdiy] DC Offset Injector?
> 
> This will do it:
> 
> http://www.buzzclick-music.com/dc_offsetter.jpg
> 

But this circuit will invert the incoming signal, right? A second inverting
amp will get it back in phase with the original. Would it be okay to use a
non-inverting summer in this case? BTW, what are the
advantages/disadvantages of non-inverting stages? I'm trying to get this
straight in my mind, and I believe I had read somewhere that a non inverting
stage can't have a gain of less than 1, meaning that everything (including
noise and HF stuff) right up to the frequency limit of the op amp gets
amplified along with the signal. Is this right or am I wrong (again)? Also,
does the 'virtual ground' concept work the same in inverting and non
inverting configurations? The vast majority of the op amp circuits I see in
SDIY use the inverting configuration, so there must be a good reason for
that.

Tim (virtually grounded) Servo
 

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