[sdiy] Rectifier for logic level pulse?

[Tim Parkhurst]

Hello Y'all,

I'm looking for a circuit that SHOULD have been a simple thing, but it
it escaping me. I have a circuit that take a CMOS level pulse,
differentiates it, and uses a diode to lop off the negative pulse that
occurs when the CMOS input goes low. Simple: one cap, one R, one D.
What I'd like to do is add another diode (or three) and "rectify" the
negative pulse. Essentially, what I need is a circuit that produces a
short positive-going pulse when the input goes low to high (that's the
easy part) AND another positive-going pulse when the input goes from
high back to low (the not so easy part). This should be simple, and I
can swear I've seen this done, but I just can't find it for the life
of me. Should be just like a full-wave rectifier, right? I'm sure it
will be a "D'OH!" moment when the solution is pointed out, but I can
live with that.


Tim ("Rectifier? I hardly even know her!") Servo
-- 
"Sire, the church of God is an anvil that has worn out many hammers."
- H.L. Hastings