Distortion Analysis of $RC$ Integrators With Wideband Input Signals.

The integrator is an important building block in circuit design and its transfer characteristic is inherently frequency-dependent. When it is implemented as an $RC$ op-amp circuit, a nonlinear element (the amplifier) is placed within a frequency-dependent feedback loop. Conventional techniques allow us to obtain the nonlinear error easily at certain frequencies only. Furthermore, when the integrator is periodically reset, the circuit is not in steady-state and conventional techniques assuming a steady-state behavior do not apply. It is not obvious how the actual error relates to the circuit parameters when the integrator is driven with a wideband signal. In this paper we present an approach to quickly estimate the normalized mean squared error (NMSE) as a function of the circuit and signal parameters. We show that, to first-order, the NMSE is proportional to the ratio of the signal bandwidth and the dominant pole of the integrator. For an integrator with reset, the signal builds up from zero and results in an additional, integration-time dependent NMSE reduction. [ABSTRACT FROM AUTHOR]