[sdiy] Rectifier for logic level pulse?

[Dave Manley]

John Mahoney wrote:
> At 07:22 PM 9/28/2009, Tim Parkhurst wrote:
>> Hello Y'all,
>>
>> ... 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). ...
>
> <brainstorming>
> Split the signal and run one side through a normal detector. Invert 
> and offset the other side; now run that through the same kind of 
> detector, because what was a falling edge is now a rising edge. 
> Combine the 2 outputs. Done. The negative side will want to send a 
> pulse on startup, I guess, so you may need to handle that.
> </brainstorming>

Look at figure 2. It is dead simple, unless there's some rule that it be 
discrete or passive, or it has some tight requirement on frequency or 
output pulse width, none of which were given.

http://sound.westhost.com/appnotes/an005.htm

-Dave