I'm looking to measure the voltage difference between two sets of p/n juntions that are likely to be a couple of degrees different in temperature. If I can get away with not adding an external op-amp, then board size and power use will be reduced accordingly.
In some microcontrollers, a programmable gain associated with their ADC actually means that the reference input to the ADC is getting divided. Is the PGA for differential measurment in the ATTiny25/45/85 really an amplifier? Does anyone know the noise characteristics?