Pulse circuit help

Question

First question: I need to make a circuit, using generic OP-AMP, that takes 5V and audio signal (mono/L/R) and flashes LED every peak.

The OP-AMP can be anything, but it must follow 8-pin layout. (Not surface-mount components)

Second question: I need to make a circuit which outputs high-pitched blips (or continuous pulse) using 555 timer. I had this circuit diagram but I lost it.

D_Hersey · Answer

Many comparators (X's) are pin compatible with (U's) op amps, so it shouldn't be hard to tell the difference in situ

(still no recovery of my period key)

One note of caution -- some comparators have open-collector or open-drain outputs and require a pull-up to display voltage output

peterjcs23 · Answer

It all depends on the accuracy of the circuit and the function. If you are just getting a LED to flash when there is a loud noise on the input to the microphone then the amplifier may be good enough. On the other hand if you want to use the output of the comparator as the input to a counter at audio frequencies say 10 to 10000Hz or you want to measure cycle periods to an accuracy of 1usec, then you would need better accuracy than the op amp can achieve and you'd use a fast comparator.

All the best, Peter

peterjcs23 · Answer

Design your circuit, post it on the blog and let people comment, I would suggest.