[sdiy] VCO Cap Switch

Scott Bernardi sbernardi at attbi.com
Thu Jun 6 06:48:12 CEST 2002

Ah. I ran mine at +/-12v supplies with the ground pin to -12v and the pullup to
ground (output switches between 0v and -12v - pretty much your circuit).
In my pulse waveshaper, I made local +/- 5v references with transistor buffered
zeners. A 4.7K pullup went to the +5v, and the ground to -5v.
See http://home.attbi.com/~sbernardi/elec/lockbox/lockbox_home.html#VCO

Ian Fritz wrote:

> At 10:00 PM 6/4/2002, Scott Bernardi wrote:
> >The datasheet shows the LM319 spec'd at 36v max, same as a LM311.
> True. But I found that to get full output swing I had to use a rather small
> (750R - 1k) pullup resistor. In my TRI oscillators this caused the chip to
> run quite hot, so I reduced the PS voltages. Tracking was then much
> improved. For a SAW oscillator this isn't a big issue.
> >The LM311 needs
> >a pullup resistor also, doesn't it?
> Not that I can see.
> Another issue with the 319 is that there aren't any good application
> schematics. I must say, I really don't know the proper way to connect the
> ground pins. I just hooked them to the - supply, but this actually violates
> one of the max ratings. May be this is why I had trouble with heating.
> >I used the second comparator in the LM319 for the pulse output (sawtooth
> >on one
> >input and PWM input on the other).
> A good plan.
>   Ian

Scott Bernardi
sbernardi at attbi.com

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