A 250-GHz Differential SiGe Amplifier With 21.5-dB Gain for Sub-THz Transmitters

Abstract

This article presents a 250-GHz SiGe amplifier composed of three differential cascode stages in a 0.13-μm SiGe BiCMOS technology (f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</sub> /f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">MAX</sub> = 300/500 GHz). The Marchand balun is utilized to implement single-ended to differential signal transformation for its superior performance over the transformer-based balun at sub-THz frequencies, which has been investigated and verified through electromagnetic (EM) simulations. A stair-like interconnection method and conventional positive feedback technique are used to improve the inherent gain of the active device. The proposed amplifier exhibits a record S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">21</sub> of 21.5 dB at 252 GHz and a 3-dB bandwidth of 11 GHz with the capability of gain control. The measured OP <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1dB</sub> is -3.7 dBm with the corresponding power added efficiency (PAE) of 0.3%, and the saturated output power is estimated to exceed 0 dBm at 252 GHz. The overall power consumption of the chip is 149 mW. Along with remarkable gain and output power, the compact amplifier is suitable to be adopted as an output block in the sub-THz transmitters.