A Broad-Bandwidth Cascode-Feedback Transimpedance Amplifier for Short-Range Optical Communication

Recently, demands in short-range optical communications with high integration are increasing very fast, and transimpedance amplifiers (TIAs) play a significant role in optical communication systems. This paper presents a broad-bandwidth TIA, which investigates the design strategy of the regulated cascode (RGC) TIA under low supply voltage. The proposed TIA includes a cascode-feedback RGC input stage with transistors working in weak inversion to achieve an optimized trade-off among bandwidth, low supply, power consumption and noise. Capacitive degeneration is used to further extend the bandwidth. In 40-nm CMOS, the proposed TIA under 1.2 V can achieve a -3dB bandwidth of 8.65 GHz with 0.25 pF photodiode capacitance and 0.15 pF load capacitance. The total input-referred noise current is $\mathbf{2.47}\ \boldsymbol{\mu} \mathbf{A}$ . The core TIA occupies 0.003 mm ² while the DC power consumption is 2.46 mW without the output buffer. Compared with related TIA works, the proposed TIA achieves comparable bandwidth performance and a $\mathbf{2}\times\sim \mathbf{3.5}\times$ figure of merit enhancement.