I was building a circuit using a Texas Instruments TL074 as a comparator, when I noticed some strange behavior. I isolated the chip and tested it with a couple of potentiometers. Basically, when I put two DC voltages on the inputs of one of the op-amps, everything works as expected except for the case where the non-inverting input is taken below about 0.8 V above Vee. Then the output swings high (when I would expect it to be low). Is this behavior common for op-amps, and is it described somewhere on the data sheet?
I don't have a TL071 to test, but I tried the experiment on a TL072 and found the same behavior. I have Vcc at +5V and Vee at -5V.
I know that I'm not supposed to use op-amps as comparators, but that's what I have on hand today.
Best Answer
Try learn something about allowed Common-mode Input Voltage Range. The Common-mode Input Voltage Range tells you the voltages at the inputs that cause them to work properly or to not work.
As for your problem look here
And here at question "What other features of op amps should the user know about? " http://www.analog.com/library/analogDialogue/Anniversary/6.html http://www.planetanalog.com/document.asp?doc_id=528175