[sdiy] Capacitor type matters in 74HCxx one-shot circuit ?

[Didrik Madheden]

The two parameters that could matter are frequency response
(self-inductance) and leakage current.
Frequency response doesn't really matter. It's just passing a pulse through
the capacitor and waiting for the capacitor to charge and flip back. It's
very noncritical.
Leakage current doesn't really matter either. Both sides are driven at all
times, so you're not relying on the capacitor to hold it's charge for long
periods like in for example a sample and hold circuit.

Something else about the circuit however, is that during the reset phase
U1's output will go high while the capacitor is charged. This will cause
the voltage at U2's inputs to go above the usual maximum voltage and
discharge the capacitor through the chip's protection diodes. This may or
may not be ok in practice but something to be aware of.

/Didrik


On Fri, 9 Oct 2020 at 16:42, Jean-Pierre Desrochers <jpdesroc at oricom.ca>
wrote:

> Does the capacitor type (Ct: ceramic or film) matter in a circuit like
> this one ?
>
> I’d say film is obviously better but.. in such a circuit… ??
>
>
>
>
>
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