HBT Power Amplifiers for Handset Applications

摘要

This paper overviews the device and circuit design techniques employed in HBT power amplifiers for handset applications including GSM and CDMA while focusing on ballast design and VSWR ruggedness for HBTs. At first the paper presents a calculation method useful for ballasting resistor design, and then shows that AlGaAs-HBT and InGaP-HBT are quite different in the effectiveness of ballasting resistors by calculation and experimental results. As an example of the additional circuit implementation for VSWR ruggedness improvement, this paper also gives a detailed introduction of an active feedback circuit design technique used for GSM handset amplifiers, and subsequently describes device and circuit design considerations for CDMA handset amplifiers.