Design of Butterworth-type transimpedance and, bootstrap-transimpedance preamplifiers for fiber-optic receivers

This paper introduces a set of design tools for maximally flat transimpedance and bootstrap-transimpedance preamplifiers driven by capacitive current sources (photodetectors). A four quadrant graphic approach is shown to provide a good insight into a variety of solutions, all of them representing Butterworth-type circuits having the required bandwidth and transimpedance. The bootstrap-transimpedance is a novel configuration suggested here which by combining bootstrapping of the detector capacitance with resistive negative feedback is proved to be superior to other preamplifiers implemented in the same technology. The design approach presented in this paper is recommended for use in the early stages of the preamplifier development, the resulting charts serving as guidelines to the design at the transistors level.