I have a pressure sensor, it has 4 wires, In+ In- Out+ Out-. I excite In+ and In- with a 12V battery and the outputs are about 6V each, the difference is very small, 0.7mV at 1atm and 12.9mV at 100psi. I want to read this with a microprocessor which takes in analog 0-5V so I want to amplify the difference (Out+ - Out-) x 50 or so. I tried a few different op amp circuits with LM318N, I tried an instrument amplifier INA2126 and after 25+ tries none of them work. The reading I get from these amplifier outputs is always 3-6V and it never changes when I put pressure on the sensor or not. So I'm giving up on the amplifiers, and my question is could I use a BJT or some kind of transistor to get the job done?