Electronic – Amplifying Millivolts with a Single Power Supply Op Amp in a Large Gain

adcinstrumentation-amplifierlow-poweroperational-amplifier

I have a signal around 1mV-10mV to be amplified. This signal should be fed into an ADC (ADS1115 ) which has minimum full scale range of 0.256V. So the gain should be at least around 300. I am thinking of doing this amplification with a single supply (5V) low power Op-amp. I went through some op amps (OPA, LM) and can't find if they are good enough as some don't have libraries to simulate and most are out of stock in our area.
I would like to know if it is possible to achieve such a gain with an acceptable accuracy (error level 5~10%) and some suggestions of particular op amp models.
Couldn't find an ADC which has lower than 0.256V full scale range, seeking for suggestions if you have any, so I wouldn't have to amplify the signals in a large factor.

Best Answer

I can't speak to component availability in your area (Sri Lanka?) but there are many op-amps that will do this. Look for Auto-Zero or Zero-drift op-amps. You can easily get relatively high accuracy with a gain of 100 or so for 100mV to 1V out using a simple non-inverting amplifier configuration.

For example, AD8551 which has a maximum Vos of 5uV and a maximum TCVos of 40nV/K. Voltage noise 0-10Hz is 1uVp-p so that should not limit the ADS1115 too much.