Low-Noise Modified-RGC Transimpedance Amplifier With Bandwidth Enhancement Using an Intrinsic Negative-RC Network

Abstract

This paper presents a dual feedback transimpedance amplifier (TIA) with a modified regulated- cascode (RGC) topology that employs a negative resistance-capacitance (NRC) network to enhance both bandwidth and noise performance. By combining a negative resistance-capacitance network with transcon- ductance boosting (gm-boosting), the proposed topology provides greater flexibility in circuit design, improving the performance of the circuit, in relation to both input and output nodes, compared to conven- tional RGC topologies. This increased design flexibility enables optimal input impedance with lower power consumption, particularly in the presence of large photodiode (PD) capacitance, while avoiding output node headroom limitations. Additionally, the use of a negative capacitance at the output node allows for increment of the output resistance (gain) without concerns about headroom limitations or load capacitance constraints, resulting in a significant noise reduction and bandwidth enhancement. To demonstrate the effectiveness of the proposed circuit techniques, the TIA topology is fabricated in 0.35 μm CMOS technology. Measurement results show 69 dB transimpedance gain, 1.7 GHz 3-dB bandwidth, and 6 pA/√Hz input referred noise current spectral density. The circuit power consumption and area are 7.4 mW and of 0.01 mm2, respectively.