The AD629ARZ is a High Common-mode Voltage Difference Amplifier with a very high input that allows the user to accurately measure differential signals in the presence of high common-mode voltages up to ±270V. This amplifier can replace costly isolation amplifiers in applications that do not require galvanic isolation. The device operates over a ±270V common-mode voltage range and has inputs that are protected from common-mode or differential mode transients up to ±500V. It has low offset, low offset drift, low gain error drift, low common-mode rejection drift and excellent CMRR over a wide frequency range.