[sdiy] Linear input on expo...confused

[Roman Sowa]

You said "a bit", while you have to mirror everything and not only 
replace NPN/PNP. For example the current setting resistor should go now 
to negative supply.
Hard to tell anything without your changed schematics.

Roman

W dniu 2014-09-09 12:13, Rutger Vlek pisze:
> Hi all,
>
> I have a fairly standard expo converter here, quite similar to this
> one
> (https://plus.google.com/107231411209962227230/posts/C8iVtXKzvet?pid=5628330677174689314&oid=103342596752795218521).
> However, I needed a current source, rather than a sink. So I changed
> the circuit a bit and replaced the NPN pair with PNPs. Besides the
> expo input, I'd like to have a linear input as well, but this is
> where I'm stuck. I was expecting the principle to be the same as in
> the current sink expo example from the link, where a resistor to the
> inverting input of the opamp does the trick. But in my case it
> doesn't... Any ideas why?
>
> Rutger _______________________________________________ Synth-diy
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