A switched differential op-amp with low offset and reduced 1/f noise

Fully differential techniques are becoming a popular method to alleviate the problem of low dynamic range in an analog VLSI environment. Low-frequency(1/f)noise contributions and input offset voltage remain, however, as two inherent difficulties in MOS analog designs. In this paper, a dynamic technique for implementing low-noise low-offset differential op-amps by time-sharing conventional single-ended output op-amps is introduced. A differential op-amp (DOA) implemented using this technique requires relatively little redesign effort, provides both positive and negative differential inputs, and demonstrates significant reduction in1/fnoise and input offset voltage over its single-ended counterpart. The op-amp is applicable in many sampled-data networks, such as in the design of SC filters, and can be easily interfaced with existing single-ended or differential networks.