Since there is no such thing as the perfect op amp, different aspects of the amp are optimized to meet the needs of different applications. Some specifications that affect DC or low frequency performance are offset voltage, input bias current, performance over temperature, low frequency noise and ground error. Specifications that are important for AC applications include bandwidth, slew rate, gain error, settling time, and distortion. A few specifications can affect AC or DC performance, depending on the operating conditions. These include common mode rejection ratio, power supply rejection ratio, the input common mode range of the op amp, and low power operation.