Enhanced linearity and efficiency of HBT MMIC power amplifiers for WCDMA applications

A novel linearizer based on a bias boosting technique is proposed, which is composed of a series transistor, a series resistor and a shunt capacitor, and across between the base and the collector of the RF HBT. The new bias boosting is realized and demonstrated through a GaAs HBT two-stage PA under the WCDMA/900 MHz band applications. At a supply voltage of 3.0 V, the PA exhibits the following results: the gain of 31 dB, Pout of 29 dBm, the PAE of 45% at the maximum output power, and inter modulation distortion IMD3 of better than 30 dBc. The performance comparisons are made between with and without the linearizer. The results show that the proposed bias boosting technique can improve both PAE and linearity, especially at the power back off region.