A 53 dB Ω~7 -GHz Inductorless Transimpedance Amplifier and a 1-THz+ GBP Limiting Amplifier in 0.13- μ m CMOS

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 CherryHooper 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 onchip 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-12at 10 Gb/s for an input current of 30 μAp-p in electrical measurement, delivering 600 mVp-pat the output of the 50-Ω 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.