[sdiy] weird PNP/NPN expo questions

[Dan Snazelle]

the reason i was using it is due to the fact that i was modifying and pasting together a few different projects/ideas. the original used an NPN with a PNP connected to it. as i wasnt sure if it was a sink or a source,  i changed the values to suit my needs and then added the opamp summer and tempco so i could get expo FM.

i wanted to ditch the weird expo altogether but wasnt sure if it was in need of a NPN Pair or a PNP pair.

sounds like an NPN pair right?

thanks



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> Date: Sat, 18 Jul 2009 10:49:48 -0600
> To: dixon at interchange.ubc.ca; subjectivity at hotmail.com; synth-diy at dropmix.xs4all.nl
> From: ijfritz at comcast.net
> Subject: RE: [sdiy] weird PNP/NPN expo  questions
> 
> At 10:27 AM 7/18/2009, David G. Dixon wrote:
>>> This is an obsolete method.  Why not just use a standard design?
>>
>>By "standard design" do you mean a design using either two NPNs for current
>>sinking or two PNPs for current sourcing, with common emitters?
> 
> 
> Correct.  Then you can add the linear FM via the ref current servo.
> 
> Ian
> 
>