An OTA with Series-Cascode-Miller Compensation and Anti-Pole-Splitting for a 360-MHz BW Low-Distortion TIA in Sub-6G Broadband RF Receivers

This paper presents a fully differential 2-stage operational transconductance amplifier (OTA) for a baseband transimpedance amplifier (TIA) with 360-MHz bandwidth (BW) aiming for applications in Sub-6G broadband direct-conversion receivers. The proposed OTA with folded-cascode input stage incorporates three techniques, including series-cascode-Miller compensation (SCMC), anti-pole-splitting path, and common-mode feedforward (CMFF) to ensure wideband and low distortion of the TIA with shunt feedback. The OTA’s BW is extended because the SCMC introduces a zero that cancels the non-dominant pole at the folding node of the OTA, while the anti-pole-splitting path generates a negative capacitance that neutralizes the parasitic capacitance. In addition, the CMFF circuit improves the OTA’s common-mode rejection ratio (CMRR) by about 20 dB. Designed in 28-nm CMOS with a 0.12-mm² layout area and 16.6-mW power consumption, the TIA demonstrates an SFDR of 103 dB for a 75-MHz, 250-mVpp output, an input-referred noise (IRN) of 85 µVrms, an in-band third-order input intercept point (IIP3) of 37.9 dBm, and an intermodulation-free dynamic range (IMFDR3) of 91.6 dB.