10 Gb/s optical receiver with continuous-time feed-forward equalization

This paper presents a CMOS 65 nm optical receiver design based on a continuous-time feed-forward equalizer (CT-FFE). A low-bandwidth front-end approach increases the mid-band gain and improves sensitivity. However, the intersymbol interference (ISI) that is introduced must be removed using equalization. The proposed CT-FFE topology mitigates the challenges of sampling present in discrete-time FFEs. In this work, a continuous-time delay is realized with a 1^st order pole/zero filter. The combination of a low-bandwidth inductorless transimpedance amplifier (TIA), CT-FFE and decision circuits dissipates 13.15 mW from a 1-V supply. The front-end has an equivalent gain of 2500Ω using a 2.7kΩ feedback resistor. It has an input referred noise of 0.32μArms, leading to an estimated noise-limited sensitivity of 4.48 μAp-p in the presence of a pad/photodiode capacitance of 100 fF. A reference design based on a conventional TIA and one-stage Cherry-Hooper amplifier achieved a sensitivity of 5.6 μAp-p and a power dissipation of 29.2 mW.