mv to v amplifier
Any real operational amplifier has two major problems:
1. offset voltage
2. thermal offset drift
The offset voltage is found at the output of the amplifier, magnified with the gain
when the input voltage is zero. Example: input zero mV, offset +3mV, gain 1000, configuration inverter. The output voltage will be -3x1000=-3000mV = -3V in the absence of any input voltage!
The thermal offset drift is adding to the offset voltage. Example: 15uV/C will add 15uV to any celsius degree temperature modification, magnified also with gain. At 20C above ambiant temperature (meaning +40C) the output will be 15uV x 20 x 1000 = 300mV
Conclusion: the output of an operational amplifier in inverting configuration may have 3000mV +/-300mV at 40C and ZERO input voltage.
You must choose either a very low offset/low thermal drift OA and use AC magnification, or use two cascaded OA and either DC with offset compensation or AC magnification.