Extending the common-mode range of difference amplifiers allows their use in a wider variety of reduced power-supply applications. The INA117 has a specified common-mode input range of ±200V when operating on standard ±15V power supplies. At power-supply voltages above ±13V, the INA117 input range is limited to ±200V by the power capabilities of its internal input resistors. On reduced power supplies, the input range is limited by the common mode input range of the internal op amp.