[sdiy] DC Offset Injector?

[Scott Gravenhorst]

This is one of the many things that an opamp or operational amplifier can do. 
The word "operational" refers to an arithmetic operation, such as addition or
subtraction.  In this case it would be used to add 2.5 volts to the input
signal.  Whatever the instantaneous value of the LFO output is, 2.5 volts would
be added and the result would appear on the output of the opamp.  

You should be able to find numerous websites that describe this in detail and
give good example schematics.  Look for "analog computer" as well.  You would
create a reference (2.5 volts) using resistors or a trimpot.  A great book is
the "IC Op-Amp Cookbook" by Walter G. Jung.

Joe Kramer <musetrap at earthlink.net> wrote:
>Hi Friends,
>
>My MS20 LFO generates a +/- 2.5v triangle wave, and this is fine for most
>of the internally patched functions.  But once you start patching out, there is
>an obvious need for a zero-to-5v wave, for instance when modulating one
>VCO against the ring modulator.
>
>Can I make a passive DC offset injector with, say, 10k resistors and
>pots and a power source--basically a mixer with the LFO as one input and
>a DC voltage as the other input?  If so, is 10k a safe all-around value?
>
>Or do I have to use an amplifier to do this?
>
>Thanks,
>Joe
>
>
>

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