Hi,
First of all, I am an absolute novice with electronics. In fact, novice is probably being generous. I know nothing. I haven't done any kind of electronics since school 4 years ago, and that wasn't particularly advanced and was all theoretical anyway.
However, I'm doing a research degree and it's become necessary for me to build a circuit as part of my apparatus. My supervisor helps me where possible, but I've encountered a problem that I can't explain and would really like to understand and know how to fix before I go back tomorrow morning, as it'll bug me all evening otherwise.
The circuit is an op-amp with a potentiometer. The op-amp is a 324, with a 9V power supply. The problem I'm having is that for some reason, the output is always very close to 9V, regardless of how the potentiometer is set, even though the voltage from the potentiometer is varying from 0V to 9V when I turn it, as it should be. I tried replacing the IC, and had the same problem but with the output value always being very close to 0V instead. I swapped the two several times, and one was always around 9V, and the other always around 0V.
From your experience, is this likely to be a problem with both ICs, or with the potentiometer, or perhaps with something else?
Here's a drawing of the circuit. It's from memory, so excuse any errors - I'm pretty sure the real thing is as it should be, although if you spot something obvious, please point it out!
**broken link removed**