triangle VCO help please

[Martin Czech]

Q7-Q9 is the Schmitt trigger.
R37-39 determine the positive feedback (hysteresis),
thus amplitude. You have to determine the levels at 
base of Q8. 

I think there are much better options today (offset?):
3080 with constant bias can also work as comparator.
Pretty fast, see Harris 3080 app note.

And dedicated comparators like 311 are also nice,
if they are used in the right way.


m.c.

:::Date: Sun, 26 Nov 2000 01:52:09 +0100
:::From: mark verbos <a0284520 at addcom.de>
:::To: synth-diy at node12b53.a2000.nl
:::Subject: triangle VCO help please
:::Content-Transfer-Encoding: 7bit
:::
:::Hello,
:::
:::I have built a triangle VCO based on the Buchla 258 and the Electronotes
:::
:::Option 2 Triangle VCO. I have a small problem.
:::http://www.simple-answer.com/258mod.jpg
:::
:::The waveforms looks  right at all the locations in the circuit (as the
:::buchla design) however insted of being +/- 2 volts at the point
:::indicated, mine is just under +/- 200 mVolts.
:::
:::Where in a triangle oscillator does that gain come from? Is that because
:::
:::of the 3080? The Electronotes one used a 3080 and the Triangle output is
:::
:::right off of it so I know that one has a bigger voltage. I have been
:::trying all kinds of things with no luck.
:::
:::can anyone help me? All the waveshaping after that point depends on this
:::
:::level being higher.
:::
:::
:::--
:::mark verbos
:::
:::"if you want something done right, build it yourself."
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