The ISL28158 and ISL28258 are micro-power precision operational amplifiers optimized for single supply operation at 5. 5V and can operate down to 2. 4V. These devices feature an Input Range Enhancement Circuit (IREC), which enables them to maintain CMRR performance for input voltages greater than the positive supply. The input signal is capable of swinging 0. 25V above the positive supply and to 100mV below the negative supply with only a slight degradation of the CMRR performance. The output operation is rail-to-rail. The ISL28158 and ISL28258 draw minimal supply current while meeting excellent DC-accuracy noise and output drive specifications. Competing devices seriously degrade these parameters to achieve micro-power supply current. Offset current, voltage and current noise, slew rate, and gain bandwidth product are all two to ten times better than on previous micro-power op amps. The 1/f corner of the voltage noise spectrum is at 100Hz. This results in low frequency noise performance, which can only be found on devices with an order of magnitude higher supply current. ISL28158 and ISL28258 can be operated from one lithium cell or two Ni-Cd batteries. The input range includes both positive and negative rail. The output swings to both rails.