Linearized InGaP/GaAs HBT MMIC power amplifier with active bias circuit

A linearizer using a base-emitter voltage predistortion of an active bias transistor is demonstrated. It is composed of an active bias transistor, a resistor, two base-emitter diodes for temperature compensation, and a capacitor for RF signal shorting. It compensates effectively both gain compression and phase advance of the power amplifier. Using the linearizer, an InGaP/GaAs HBT MMIC power amplifier is evaluated for W-CDMA application. The linearizer improves input 1 dB compression power by 17 dB and phase distortion by 19.89/spl deg/ for the HPSK modulated signal at the input power of 3 dBm, and doesn't show any significant increase of RF signal loss and chip area. The linearized two-stage HBT MMIC amplifier exhibits power added efficiency of 37%, a linear power gain of 24.5 dB, and an output power of 28 dBm with an ACPR of -44.5 dBc at 5 MHz offset, under a 3 V operation voltage.