Low‐noise and low‐sensitivity filters using current‐mode coupled biquads

Abstract

Summary In this paper, it is shown that by adding coupling to biquad pairs to obtain a fourth‐order band‐pass filter, the output thermal noise is reduced. It is shown analytically that minimum output thermal noise is obtained when the biquads are identical and the negative‐feedback factor used for coupling is the same as for the minimum sensitivity to component tolerances and ambient changes. Furthermore, by optimizing the coupled biquads for maximum dynamic range, the output noise is further decreased.

Noise and sensitivity comparison for different BP filter designs

“…This is important because of the decision to choose appropriate tolerance of elements for the application of a filter. In this paper, designs, based on OA, OTA-C and SC realization techniques to reduce noise [4] and sensitivity [5,6] in a filter, will be shown. This paper is an extension of the conference paper [4].…”