Efficiency enhancement for power amplifiers using dynamic bias switching technique

A dynamic bias switching technique is presented which discretely switches supply voltages according to the signal envelope level. For the detected envelope signals which are lower than an appropriate threshold, this technique dynamically switches the transistor's drain bias to a significantly lower voltage. For verification, a dynamic bias switching system, applied to a class-AB power amplifier for the 859 MHz band, was implemented. Using a down-link wideband code division multiple access (WCDMA) signal, improved output power of 0.5 dB from 30.5 to 31 dBm, and improved PAE of 8.1% points from 27.4 to 35.5% were achieved at a given ACLR level of -30 dBc compared to the conventional single-supplied class-AB amplifier.