The Design Of GaAs HBT-MMIC Power Amplifier

This paper based on the task " Research and Development of RF chip, devices andmodule facing IMT-Advanced broadband wireless communication system ", which isthe sub-topic of National Science and Technology Major Project "The new generationbroadband wireless mobile communication network ", designed a MMIC poweramplifier at2.3GHz working frequency, which is according to the application ofIMT-Advanced, the "4G" communication standard.The design of amplifier is based on GaAs HBT process technology, achieved thetargets of high power gain, high output power and high efficient, with two-stagestructure. In this paper, the key issues of power amplifier design are analyzed, andsome effective solutions has been proposed. The adaptive linear bias circuit isdesigned for providing offset-voltage to the transistor, at the meantime, the reducingbase-emitter voltage of the power tube due to the high power input is compensated,the amplifier’s offset point is also maintained constant, and the phenomenon of gaincompression is inhibited. In addition, the temperature drift phenomenon of the DCbias point and the current gain collapse phenomenon due to the self-heating effects iseffectively inhibited by the temperature compensation circuit in the bias networkusing the thermoelectric negative feedback characteristics of HBT power devices.Through adding a RC parallel stable network in the base of each power tube, thepotential instability of the transistor are eliminated, and the electrical and thermalstability of the circuit is improved. In order to simulated more precisely, thesimulation model of the bonding wire on the test chips is established. The maximumgain is realized by conjugate matching the first-stage power amplifier, the powermatching principle is adopted according to the maximum output power design of thelast stage amplifier power. Ultimately, the parasitic effect is considered sufficientlyduring the layout designing and PCB testing.The testing results of two-stage GaAs HBT power amplifier chip after the PCBcommissioning show that the power gain of amplifier is31.1dB in the small signal,P1dB is29.6dBm, PAE is55%, and it has a very good linearity performance, thespecification requirements of design is successful implemented.