An integrated capacitively coupled transformer and its application for RF IC's

Abstract

This paper describes a low voltage topology that uses a passive element that is described as a "capacitively coupled transformer" (CCT). This structure can be easily implemented using an IC technology that supports both on chip MIM capacitors and high Q-inductors. The structure is used to design a low noise amplifier at 1.9 GHz. The LNA consumes 4 mA of current has a input IP3 of -4.5 dBm, a noise figure of 2.3 dB for a source resistance of 50 /spl Omega/, a minimum noise figure of 1.9 dB, and a gain of 10.1 dB. The topology maintains a high linearity without sacrificing noise figure and gain for a supply voltage of 1 V.