IEEE journal of solid-state circuits vol:42 issue:3 pages:551-562
In this paper, a fully integrated 0.13-mu m CMOS RF power amplifier for Bluetooth is presented. Four differential amplifiers are placed on a single chip and their outputs are combined with an on-chip LC balun structure. This technique allows to have a low impedance transformation ratio for each individual amplifier, and thus a lower power loss. The amplifier achieves a measured output power of 23 dBm at a supply voltage of 1.5 V and a drain efficiency of 35% and a global efficiency of 29%. The parallel amplification topology allows to efficiently control the output power which results in an efficiency improvement when the output power is reduced.