ODP: thru zero VCO questions

[harry bissell]

You can make a circuit with a CMOS schmitt trigger which will "spray" pulses
once an input level is achieved... the delay to the pulse "spray" is a little
longer than the rest of the pulses. I believe I used a CD4093 to do it... If
you add this stage after the comparitor, if the input (comparitor) doesn't go
away, you can force it.

I'll try to remember exactly how I did this if anyone is interested...

:^) Harry

Rene Schmitz wrote:

> At 10:23 09.09.99 +0200, you wrote:
> >My advise is this:
> >don't look at other designs. If you have simpler idea - try it.
> >As a matter of fact I wanted to do something exactly like your idea,
> >but due to epidemic disease eating free time I didn't.
> >What bothers me is, when the D-flop was just toggled, integrator
> >voltage started to travel from max to -max, and FM input changed polarity,
> >then D-flop should change again really soon.
> >OK, little histeresis on window comparator would solve nose-switching
> >problems, but what if it all happens really close the maximum integrator
> >voltage, near the switching point? VCO will lock at opamp maximum voltage.
> >OTOH such condition might appear once in a milion years during
> >normal use.
>
> Right this is a problem. Once the thresholds are exeeded, the comparators
> cannot "flip the flop" anymore. Maybe check the locking condition with a
> second pair of comparators and bruteforce discharge the cap would help.
>
> Bye
>  René
> error:asciiartisnotfully  \ uzs159 at uni-bonn.de
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>