A highly stable V-band balanced power amplifier has been proposed based on MMIC using the pseudomorphic High Electron Mobility Transistor (pHEMT). The amplifier consists of two stages with device length of 8 × 25 µm and 2 × 25 µm gate widths. The design kit of PP10 WIN Semiconductor Corp. has been used. The simulation results show power and gain levels of 18 dBm and 12.5 dB, respectively, with a tolerance of ±0.8 dB over the broadband range of 40–80 GHz. Microstrip Lange couplers are used as 3 dB quadrature power splitters and combiners. The amplifier has an acceptable performance with low input and output VSWRs, high stability, fairly flat gain and constant power over the whole bandwidth; and so it can be a good candidate for broadband millimetre-wave front end transceivers systems, and also, as an instrumentation amplifier in measurement systems.