Bandwidth Extension of Resistive-Feedback CMOS Inverter Amplifier Using T-coil Peaking

This paper presents a broadband CMOS three-stage resistive-feedback inverter (RFI) amplifier for high-speed applications. A novel T-coil-based peaking technique is proposed, combining over-shunt and gate peaking to extend the bandwidth with reduced inductance. Theoretical analysis derives design equations and shows that the proposed structure achieves a bandwidth extension ratio of 2.3, matching conventional gate peaking performance with only one-third the inductance, thereby enabling chip area reduction. Fabricated in a 28 nm fully depleted silicon-on-insulator CMOS process, the amplifier occupies an active area of only 0.0094 mm². Small-signal measurements show a gain of 16.2 dB, a 3-dB bandwidth of 31.5 GHz (gain-bandwidth product (GBW) = 203.38 GHz), and low power consumption of 5.6 mW. The measured eye diagram confirms reliable performance, with an output amplitude of 333.4 mV pp , signal-to-noise ratio of 8.9, rise time of 15.0 ps, and fall time of 15.3 ps, meeting the 28 Gbps non-return-to-zero signaling requirements. Compared to previous broadband CMOS amplifiers, the proposed T-coil peaking RFI amplifier demonstrates superior GBW performance in terms of active area and power consumption.