A 53 dB<inline-formula> <tex-math notation="LaTeX">$\Omega~7$ </tex-math> </inline-formula>-GHz Inductorless Transimpedance Amplifier and a 1-THz+ GBP Limiting Amplifier in 0.13-<inline-formula> <tex-math notation="LaTeX">$\mu$ </tex-math> </inline-formula>m CMOS

Abstract

An inductorless 10-Gb/s optical receiver including a novel transimpedance amplifier (TIA) with dual feedback loop and a limiting amplifier with third-order nested feedback is presented. The current-buffer-based TIA employs an active Cherry-Hooper stage in the auxiliary amplifier and reuses the tail current source to achieve 10 Gb/s operation in the presence of a 1 pF photodiode input capacitance. Systematic analysis and design methodology of the double loop TIA is given with simple design equations derived for optimizing the performance of each loop. The use of nested feedback in the four stage limiting amplifier enables a gain-bandwidth-product >1 THz without the use of on-chip inductors. It is shown that the proposed limiting amplifier circuit enhances bandwidth by utilizing inherent equalization between the overdamped and underdamped poles. Implemented in IBM 130-nm CMOS technology, the optical receiver achieves a BER $ at 10 Gb/s for an input current of $30\,\,\mu \text{A}_{\mathrm{ p-p}}$ in electrical measurement, delivering 600 mV $_{\mathrm{ p-p}}$ at the output of the 50- $\Omega $ buffer. Optical testing confirmed −17.4 dBm sensitivity for a data rate of 7.5 Gb/s, which is limited by the maximum speed of the 850-nm source available at the time of measurement. The receiver dissipates 108 mW from 1.2-V supply (excluding the output buffer) and occupies a core area of only 0.08 mm2.