Investigation of a switched-capacitor integrator-pair with low-sensitivity to non-ideal op-amp effects

A switched-capacitor (SC) integrator-pair consists of an inverting and a noninverting integrator which may be connected together to form a two-integrator loop, an essential component in many filters. In some situations the integrator circuits are required to have especially low sensitivity to nonideal operational amplifier characteristics such as finite gain, input offset and noise. This may arise, for example, when op-amp gain has to be sacrificed for bandwidth, or in GaAs MESFET technology, where high transistor output-conductance increases the required complexity for high-gain op-amps, and where 1/f noise is a particular problem. This paper reviews existing circuits with low sensitivities to these effects, including a new integrator-pair recently proposed by the authors. The principal advantages of this integrator-pair is highlighted by comparing equivalent analytical expressions and simulation results with those for conventional SC circuits. The outcome of the practical studies is presented, both to support theoretical results, and as a means of assessing the importance of effects that do not allow easy simulation or analysis