Friends,
I am trying to use PIC16F1789 uC's internal Opamp as Differential amplifier. I want to measure 0 to 100 Ohms resistance. I have converted this resistance to 17.8mV to 33.9mV using simple wheatstone brdige. I have tried making differential amplifier using 1Mohm & 39Kohm resistors pair. Gain should be somewhat 25. FVR set to 4.096volt. but the result I am getting is 3.19 volt & 3.65 volts. which tells the gain is coming 107.6 & 179.2 . why the gain is changing & whether I can use the internal opamp as differential amplifier or not?
Pins RA4 and RA5 used for OPA ? Are they OPAxIN+ and OPAxIN- pins ? Have you disabled any other multiplexed function on these pin like ADC, Comparator, etc... ?