A Wide-Band Complementary Digital Driver for Pulse Modulated Single-Ended and Differential S/C Bands Class-E PAs in 130 nm GaAs Technology

Wide-band digital drivers are indispensable for SMPAs (Switched Mode Power Amplifiers) in PWM (Pulse Width Modulation) and PPM (Pulse Position Modulation) applications. This paper presents the design of a wideband RF pre-amplifying buffer, innovated for very low dropout and low power complementary operation in heterojunction technologies affording only depletion type devices. A simple, passive bias level shifting technique is also incorporated to facilitate interfacing the digital modulator in silicon substrate with the PA in III-V wafer. In order to experimentally validate the concepts, the proposed driver is employed for driving an S-band single-ended class-E PA as well as for its differential version, modified to switch over S and C bands, in 130 nm GaAs pHEMT technology. The output powers of the differential amplifier are combined using on-chip transformer balun. Test results of both chips demonstrate that the implemented drivers consume less than 4% of the overall PA efficiencies, wherein the buffer responds linearly to the wideband input pulses when tested alone.