[sdiy] Hmmm...OK NOW you can panic :(

[Harry Bissell Jr]

That sounds more like the gain control cell from
Rene Schmitz or Juergen Haible's SSM2040 clone.

I thought Tom's circuit was a passive Opamp... otoh
maybe I never saw that one

H^) harry

--- mark verbos <mverbos at earthlink.net> wrote:


---------------------------------
    Tom G's method was simply a pair of NPNs, a pair
of PNPs and an extraNPN at the bottom for the control
path. The single NPN can be removed,as in Don and
Ian's oscillators, allowing an NPN pair for expo
control.It doesn't seem too bad to end up using 6
transistors insted of an 8pin chip and a matched pair.
They do need matching tho, so that makesit a little
harder. You could use 3 matched pairs. How does the
noisespec compare though (not that the 3080 was a
shining example of how tobe quiet)?

Mark


harrybissell wrote:
  
You might do it with a bunch of monolythic quads... it
will be toughbecause the mirrors MUST use diode
connected transistors as the diodesin the circuit. It
will NOT work with diodes.I do this as a spice model
all the time.H^) harrymark verbos wrote:  
      
TomG made a discrete model of the 3080 a long time
ago. I never builtone, but I have built some of the
buchla oscillators that have a similardiscrete OTA.
The good thing when you build them from the ground up
isthat you can run 'em from an NPN expo converter AND
can add a symetrycontrol.MarkTony Clark wrote:    
          
  Hi List,  Well this officially sucks.  Now if only I
could find a "life-time"buy of those elusive 3080M's. 
I bought up a bunch a while back when Iknew supply was
getting limited, but this throws a HUGE monkey
wrenchinto any future designs I make...  Anyone got a
good discrete or semi-discrete OTA design they'd
bewilling to share?  Evidently it's time to get
re-aquainted with thebreadboard and the 3080
schematic...  Cheers, 
Tony-----------------------------------------------------------------------
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