one shot

[Maarten Halmans]

Hi all,

today I finished my first module, an envelope generator. Not really
spectacular, but it works fine. I used the Elektor formant envelope
generator and added an inverted output and different timing caps to
create short and long adsr cycles. The formant adsr is retriggerable so
I want to add a retrigger input. To retrigger it, the gate must be
pulled to ground for a couple of microseconds. To create this short
pulse I need a one shot. The one shot should be triggered only once on a
positive edge. What's the best way to construct this? Should I use a
555, a comparator or an IC like the 74121?.

Any help would be appreciated,

Maarten