A 56-Gb/s PAM4 Continuous-Time Linear Equalizer with Fixed Peaking Frequency in 40-nm CMOS

This design presents a 56-Gb/s PAM4 CTLE in 40-nm CMOS. By adopting capacitive degeneration, inductive peaking, and inverter-based TIA, the two-stage CTLE generates a high-frequency peak which can compensate the gain attenuation due to channel loss at required Nyquist frequency. Through tuning the source degenerated capacitor of the first-stage gm-cell and the feedback inductor of the second-stage inverter-based TIA, the designed CTLE can achieve an 8.6-dB tuning range at the fixed peaking frequency of 22 GHz. The proposed structure reaches a DC-gain at-0.6 dB from a 1-V voltage supply, which can recover the eye diagram of the 56-Gb/s PAM4 signal from distortion due to the 8.6-dB channel loss at Nyquist frequency.