Hi folks, I’ve been trying to use LM311 to compare for a simple project, and it is depressing (to say the least) that my friends and I have not been able to get the comparator to work, I suspect that it is due to a knowledge gap, but our lab instructors keep saying, well the equipments here are for Educational Purposes and no one certifies them, and the LM311’s are cheap and unreliable so it’s not a big deal to not be able to compare voltages properly, for your project get IC’s which are reliable and more expensive I personally hate this mindset, what are your thoughts, and if the problem indeed is knowledge gap (which it certainly is according to me, as I don’t fully understand why the heck you need a pull up resistor with the thing) then do please tell me what I should be doing to catch up.
Thanks a lot for going through this post… All answers are appreciated.
P.S. the project involves comparing a sine wave to get a square wave which is then fed to a T flip flop (made using JK flops that we have) to generate phase shifted waves as shown in the image attached, which is an LTspice simulation with the LM741s
Made this two hours back, going to go and simulate this in the lab now, will get back with results later.
Looking at the datasheet for the lm311, the output is a transistor (I think it’s shown on your schematic), the reason you need a pull-up on it is because it has no bias or power. That will let it pull the voltage down. If you’re noting that it doesn’t rise fast enough, try making that 100k smaller, give it some more strength.
. The 741 on the other hand has a pair of transistors on the output stage, attached to +v and -v so it can push and pull the output