Low distortion RF-LDMOS power transistor for wireless communications base station applications

In this paper, an LDMOS power transistor design is described, having a square-law approximated transfer characteristic to obtain very low distortion in class-AB operation. Compared to conventional LDMOS transistors, significant linearity improvement is achieved over a large power range. Measurements on a 30 W/2 GHz transistor demonstrates 5 to 10 dB improvement in intermodulation distortion (IMD) and single-carrier adjacent channel leakage ratio (ACLR) for WCDMA in the back-off region. The new LDMOS is very suitable for multi-carrier amplifiers in 3G system.