A 50MHz bandwidth multi-mode PA supply modulator for GSM, EDGE and UMTS application

This paper describes the design and measurement results of a supply modulator for a PA for GSM, EDGE and UMTS application. The modulator combines a high-bandwidth class-AB linear regulator with an efficient DC/DC converter in a master-slave configuration. The DC/DC converter is current-mode controlled and has been designed to operate at switching frequencies between 1 MHz and 25 MHz. A damped dual-inductor LCR filter has been inserted in the output branch of the DC/DC converter for ripple suppression. The chip has been fabricated in a 0.25 mum CMOS process with an additional gate oxide for 6 V transistors and has an active area of 1.5 mm². It achieves a bandwidth of 50 MHz (for UMTS) with a peak output power of 3.2 W (for GSM) and output rms ripple of less than 4 mV.