I am currently working on a project where I'm using an op-amp as a comparator (lm747). I set it up as a non-inverting op amp. It's my understanding that when the voltage at the inverting input is more than the non inverting input, the output should be about 0 (I have the minus pin of the op amp tied to ground) and when the voltage is greater at the non inverting input, the output goes high to Vcc.
I put it all together and for the most part, it works, except that when the voltage is greater at the inverting input, I do not get my output to be 0 or ground, instead, it stays at 2v the whole time. I'm really stumped about this. I even tested the op-amp without any other parts and I still get the 2v at the output when it should be 0.
Here is the circuit that I am using:
http://home.cogeco.ca/~rpaisley4/ComparatorCdS.GIF
except my LED goes to ground instead of Vcc because I want it to come on when the light sensor detects light and off when there is no light present.
I've switched the op amp chip thinking it might be a bad chip but I get the same result.
Any advice would be appreciated, thanks!
I put it all together and for the most part, it works, except that when the voltage is greater at the inverting input, I do not get my output to be 0 or ground, instead, it stays at 2v the whole time. I'm really stumped about this. I even tested the op-amp without any other parts and I still get the 2v at the output when it should be 0.
Here is the circuit that I am using:
http://home.cogeco.ca/~rpaisley4/ComparatorCdS.GIF
except my LED goes to ground instead of Vcc because I want it to come on when the light sensor detects light and off when there is no light present.
I've switched the op amp chip thinking it might be a bad chip but I get the same result.
Any advice would be appreciated, thanks!