A 112-Gb/s PAM-4 Linear Optical Receiver in 130-nm SiGe BiCMOS

In this paper, we present a linear optical receiver for 112-Gb/s PAM-4 optical link. We propose a transimpedance front-end that optimizes thermal noise, power supply noise rejection, linearity and bandwidth altogether. The pseudo-differential structure is employed to achieve both low thermal noise and good power supply noise rejection. A transimpedance amplifier (TIA) gain control technique is proposed to improve linearity at both topology and transistor level while maintaining stability. An NIC-CTLE combo extends bandwidth with optimized frequency response. Designed in a 130nm SiGe BiCMOS process, the receiver realizes 37 GHz total bandwidth and input-referred noise of 19.8 pA/√Hz. The transimpedance gain can vary from 70 dB Ω to 50 dBΩ, which enables maximum input overload current of 1.8 mApp with < 5% THD at differential output swing of 600 mVpp. The receiver consumes 77mA from 3.3V supply.