Single-Supply Measurement Amplifier

This circuit is eminently suitable for adding bipolar input capability to the unipolar A/D converter of a microprocessor circuit (in a data logger, for example), without having to use a dual power supply.A bipolar input stage normally takes the form of two amplifier stages powered from a symmetrical supply. The first stage functions as an input buffer, with an input impedance of 1 M?. The second stage adds an offset to the buffered input signal, to make it suitable for the following unipolar ADC.