Re: Accurate(ish) frequency measurement

Michael Brown wrote:

The questions (finally!) are
1) Is this the sensible way to do it?
2) Slew rate and switching delay for the capacitor charging (and to a letter degree, the discharging) circuit is obviously important. From a back of the envelope calculation even a BC109 seems to be able to do the job, but that seems too easy. A MOSFET + driver is mess that I'd rather avoid.
3) Any nasty hidden surprises in these types of circuits that I should keep an eye out for when designing it?


Capacitors have a nasty habit, to arrive at charging/discharging level to 1% accuracy you need ~ 3RC (time constants) or precise and fast comparators.

Stanislaw.
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