Odp: [sdiy] crazy CMOS behavior

[harrybissell]

Without knowing the supply voltage... I'd say that a 10K would be fine...
that would only be a 1.5mA load at 15V.  Probably a 100K would be
enough.

H^) harry

mark verbos wrote:

> As it turns out, the problem was related to the load input. I am using
> an analog switch to decide if the trigger in is going to the step input
> or the load input. I had to tie both to ground with a resistor so when
> the switch is the other way they won't "float". I was using a 456k
> resistor (it's what was laying around) and I guess it wasn't strong
> enough to keep the load input from floating, because it was.
>
> My question is, what value is enough to keep it down, but not too much?
> Do I need to switch between the trigger in and ground? That would result
> in a PCB change, that I hope to avoid.
>
> thanks...
>
> mark
>
> Roman wrote:
>
> >probably your CMOS inverter is oscillating because it is driven with
> >too slow transients. RC network driving transistor will cause such
> >slow changes. You can use smaller cap, or better - schmit gate
> >40106, or 4006, can't remember the name.
> >
> >Roman
> >
> >----- Original Message -----
> >From: mark verbos <a0284520 at addcom.de>
> >To: synth DIY <synth-diy at dropmix.xs4all.nl>
> >Sent: Wednesday, October 02, 2002 7:30 PM
> >Subject: [sdiy] crazy CMOS behavior
> >
> >
> >>I have built a sequencer based on the 4516 counter. The clock input is
> >>stolen from the Serge TKB schematic that is on music machines. That is,
> >>trough a cap to an NPN then a CMOS inverter then to the counter. When I
> >>clock it, with anything, it jumps all over the place with no real sense
> >>or pattern. Could this be related to the step length not being right?
> >>How does it work for the actual Serge? It's not the chips, I have
> >>switched them all out and it does the same tihng. Am I just missing
> >>something not grounded or something?
> >>
> >>thanks for any ideas, I'm going nuts here.
> >>
> >>mark
> >>
> >
> >