A design methodology to extend bandwidth for regulated cascode transimpedance amplifier

Abstract

This brief analyzes the performance of regulated cascode (RGC) topology and develops a broadband transimpedance amplifier (TIA) incorporated with a novel dual shunt-feedback configuration. Compared to traditional RGC circuit, the proposed TIA improves the natural frequency and optimizes the damping factor. Furthermore, the common source auxiliary amplifier is replaced by an inverter amplifier to provide extra gain and reduce the equivalent input noise current. Based on 0.18-µm CMOS technology, a TIA with enhanced RGC structure was optimized and implemented, and the fabricated chip was mounted on a Rogers 4003C printed circuit board. The experimental results demonstrate a 5.2 GHz bandwidth and a 60.5 dBΩ transimpedance gain for 0.5 pF photodetector capacitance. The fluctuation of group delay is less than 50 ps, and the measured average equivalent input noise current density is about 14.99 pA/√Hz. The chip consumes 28.4 mW using 1.8 V supply.