High Linearity Transmit Power Mixers Using Baseband Current Feedback

Abstract

Transmit mixers frequently use Gilbert cells driven by common-source baseband amplifiers. Class-AB biasing is used in the latter for high efficiency, but this causes poor linearity. In this article, linearity is enhanced by using negative feedback to directly sense and linearize the baseband current flowing into the switching pair of the mixer. By suppressing both gate- and drain-induced nonlinearities, it achieves higher linearity and permits a higher power output compared to using replica devices