A Low Noise 28Gbaud/s Linear PAM4 Receiver Front-End for Optical Communication Applications in 0.13μm BiCMOS Technology

Abstract This paper presents a low noise 28 Gbaud/s linear receiver front-end for fourth-order pulse amplitude modulation (PAM4) signal applied in the field of optical communication. The designed receiver front-end includes a transimpedance amplifier(TIA), an automatic gain control (AGC) and a DC offset cancellation (DCOC) circuit. The pseudo-differential structure of the TIA is designed to achieve low noise. The resistance and capacitance degradation technology are introduced in the variable gain amplifier(VGA) and the equalizer(EQ) to improve linearity and optimize the bandwidth. In the AGC mode, the feedback loop controls the output amplitude to be a desired value within a large range of input current. The PAM4 optical receiver front-end achieves a maximum differential transimpedance gain of 76 dBΩ and -3dB bandwidth of 27 GHz. The equivalent input noise current density with the front-end circuit is 11.2 pA / Hz . In 0.13µm BiCMOS technology, the PAM4 front-end chip consumes 200 mW with a 3.3V voltage supply.