In this paper, a 4-channel, 100 Gbps inductorless optical receiver analog front-end fabricated in a 55 nm bulk-CMOS technology is presented. Active feedback technique is widely adopted to improve the performance of the optical receiver without the area-occupied inductors. To alleviate the voltage headroom stress of the local feedback loop in traditional regulated cascode transimpedance amplifier, the common gate amplifier is inserted before the traditional common source feedback stage. And the

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... ross-couple active feedback stage provides a negative signal path to extend the bandwidth of the local feedback loop. Multistage limiting amplifier with active negative and positive feedback stages are employed to extend bandwidth and acquire high gain simultaneously. The optical receiver was realized as 4-element arrays occupying the area of 800 µm × 1800 µm, whereas the core area of each channel is just 275 µm × 650 µm. The measured 3-dB bandwidth reaches 22.8 GHz, sufficient for 25-Gbps operation. For an input voltage of 2.5 mV p-p , the optical receiver achieves a BER = 10 −12 at 25-Gbps PRBS7, and 310 mV differential output voltage is delivered. From the supply voltage of 1.2 V, the test chip consumes the power of 226 mW and exhibits the power efficiency of 2.3 mW/Gb/s, when 25-Gbps PRBS31 is supplied. INDEX TERMS Active feedback, cross-coupled feedback, limiting amplifier, negative and positive feedback, optical receiver, transimpedance amplifier. GAOLEI ZHOU received the B.S. degree from Soochow University and the M.S. degree from Tianjin University, Tianjin, China, where he is currently pursuing the Ph.D. degree. His current research interests include semiconductor photodetectors, high-speed optical receiver, and CMOS analog integrated circuit.