comparator as a pulse generator

Hello,

I cannot seem to make it work..

I have a voltage comparator (LM301),

I insert to (both) its inputs varying voltages,

and I am assuming that every time (and for as long as) the + input has a greater voltage than -input,

the comparator should trigger a pulse (of variable duration in accordance to differential input) that goes from 0 volts to "supply voltage" volts (9V in my case, I am using a dual voltage supply made with batteries).

The input(s) is filtered-low-frequency-audio content.

So, assuming the input (audio, i.e 100Hz) has an envelope duration of 20ms, the pulse's duration should be (in theory-works also in workbench) about 4ms.

But instead of having a pulse at LM301 output, I have a very low signal there (maybe less than millivolts) that looks more like a triangle waveform and less like a pulse.

Can u tell what is wrong..??

I am suspecting that differential input is very low, could that be the case..??

Many thanks in advance,

xmat.

for starters the LM301 is an opamp and not a comparator, that is not to say an OPAMP cannot be used as a comparator, except a comparator has a higher open-loop gain and their slew rate is alot higher

https://www.electro-tech-online.com/custompdfs/2005/01/LM301.pdf

Styx said:

for starters the LM301 is an opamp and not a comparator, that is not to say an OPAMP cannot be used as a comparator, except a comparator has a higher open-loop gain and their slew rate is alot higher

https://www.electro-tech-online.com/custompdfs/2005/01/LM301-1.pdf

Click to expand...

sorry, I meant LM311....not that good in coordinating what I think to what I type..that type of hour..

Hope someone could help.

LM311 needs pullup on the output to +V

yup that was going to be my next point IF it was the comparator I was thinking - in fact most of them

open-collector ouput

easy mistake to do. take a 3.3k resistor from the output to +5V

thanks fro the help, still problems..

Hello, many thanx for the help, I must admit I should have used a pull-up resistor.Good point.

But I think I have encountered another problem...soo silly..I used a 9V supply voltage...and I think LM311 max Sup/Volt is 5 Volts, right??

So, are there any suggestions about a 9V supply voltage comparator?

If u have anyone in mind, does it still need to have a pull up resistor?

Many thanx in advance,

xmat.

PS:In case u know, what r the key elements of a comparator for such a use??(as a pulse generator of differential input voltages caused by audio -low- frequency content)..I mean, high slew rate, hysterisis, high open loop gain and anything else??

LM311 can operate from 5V up to 30V, so don't worry about 9V.For open collector always need a pull-up resistor. This is a big advantage, when You need a TTL output, just pull-up to 5V and the comparator supply can be e.g.20V.