I wonder Cjdelphi... If you have ANY IDEA of the photodiode current available in that circuit or the gain of the Op-Amp?. Stretching the pulse is trivial.. A half monostable from a 40106 or a 4584 will serve nicely.. It is possible too, to use a 4069UB to do all of it with 3 sections connected as a linear amplifier 40 DB of gain can be easily realized and the remaining 3 sections can clean up and delay the pulse. The down side is that the 4069 isn't very fast because it is unbuffered..I would suggest that in the future you supply schematics to back up your rather unusual? claims.Doc
Another way might be to use a dalington transistor pair or 2 transistors biased to amplify the signal then feed it through a schmitt trigger to clean the waveform up .
The one-shot timer is triggered on the falling edge of the input (pin 2).For the output to return low, trigger must return high.
Thanks for the replies. I didn't know about the interrupts, a test shows it works rather well and saves me having to add a 555 timer
So why do you still want to stretch the pulse? Provided the pulse is at least a few microseconds long, you don't need to stretch it, if you use it to trigger an interrupt.