A 50-MHz Bandwidth and 50.6-dBm OOB-IIP3 Transimpedance Amplifier Based on a Three-Stage Pseudo-Differential OTA

A 50 MHz bandwidth (BW) transimpedance ampli-fier (TIA) is designed for 5G Sub-6GHz SAW-less current-mode receivers (RX). It's based on an operational transconductance amplifier (OTA). To tolerate blockers, the TIA must exhibit excellent in-band (IB) and out-of-band (OOB) linearity, which in turn requires OTAs with high BW and gain. Traditional two-stage OTAs struggle to achieve this under low power consumption (PC), so this paper employs a three-stage OTA. A pseudo-differential structure without the tail current source is used to accommodate low supply voltages (Vdd). Differential-mode (DM) stability relies on feedforward (FF) compensation within the OTA and zero compensation in the feedback network. Common mode (CM) is stabilized by five different common mode rejection (CMR) techniques. The circuit is designed and simulated in a 40 nm low power (LP) CMOS technology with a Vdd of 1.2V. The post-layout simulation results show that when IM3 is set to 30 MHz, the TIA's IB and OOB IIP3 reach 31.6 dBm and 50.6 dBm, respectively. The minimum input-referred noise (IRN) is 5.14 $\mathbf{nV}/\sqrt{Hz}$. The corresponding FoM value is as high as 186.3 dBJ-1, exceeding all previous designs. The chip consumes 10.4 mW of power and occupies only 0.016mm2.