I am constructing a temperature data logger. The output voltage of the 741 amplifier is connected to PORTA(analouge input pins) of PIC16F876 microcontroller. The output voltage reduce after connected to microcontroller. Can anyone tell me what's the problem and how to solve this problem?? By the way, the 741 operational amplifier need +5V and -5V voltage supply. Can a voltage inverter used to generate -5V supply??