The INA117P is a precision unity-gain Difference Amplifier with very high common-mode input voltage range. It is a single monolithic IC consisting of a precision op-amp and integrated thin-film resistor network. It can accurately measure small differential voltages in the presence of common-mode signals up to ±200V. This high common-mode voltage INA117 amplifier inputs are protected from momentary common-mode or differential overloads up to ±500V. In many applications, where galvanic isolation is not essential, the amplifier can replace isolation amplifiers. This can eliminate costly isolated input-side power supplies and their associated ripple, noise and quiescent current. The amplifier's 0.001% nonlinearity and 200kHz bandwidth are superior to those of conventional isolation amplifiers.