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Tom G's method was simply a pair of NPNs, a pair of PNPs and an extra
NPN 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 8
pin chip and a matched pair. They do need matching tho, so that makes
it a little harder. You could use 3 matched pairs. How does the noise
spec compare though (not that the 3080 was a shining example of how to
be quiet)?<br>
<br>
Mark<br>
<br>
<br>
harrybissell wrote:<br>
<blockquote cite="mid415A4A3D.D436FE41@prodigy.net" type="cite">
<pre wrap="">You might do it with a bunch of monolythic quads... it will be tough
because the mirrors MUST use diode connected transistors as the diodes
in the circuit. It will NOT work with diodes.
I do this as a spice model all the time.
H^) harry
mark verbos wrote:
</pre>
<blockquote type="cite">
<pre wrap="">TomG made a discrete model of the 3080 a long time ago. I never built
one, but I have built some of the buchla oscillators that have a similar
discrete OTA. The good thing when you build them from the ground up is
that you can run 'em from an NPN expo converter AND can add a symetry
control.
Mark
Tony Clark wrote:
</pre>
<blockquote type="cite">
<pre wrap=""> 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 I
knew supply was getting limited, but this throws a HUGE monkey wrench
into any future designs I make...
Anyone got a good discrete or semi-discrete OTA design they'd be
willing to share? Evidently it's time to get re-aquainted with the
breadboard and the 3080 schematic...
Cheers,
Tony
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