A highly efficient and very compact power module using GaAs MESFETs has been developed for cellular telephones. The very-high-performance FETs, PPO (poly-phenylene oxide) printed board, and 1005-type chip C/Rs are mounted inside a very small frame of 0.8 cm/sup 3/. The load impedance of the first FET in the module is set at 50 Omega in order to satisfy the stability of the module to prevent oscillation. The typical RF properties of the module are as follows: an output power of 32.3 dBm and a power-added efficiency of 65% at a frequency of 930 MHz, an input power of 7 dBm, an operating voltage of 4.7 V.<<ETX>>