A MMIC power amplifier operating with a single-supply (3.0 V) has been developed for 5.8 GHz Japanese Electronic Toll Collection (ETC) System. The present MMIC contains two FETs, matching circuits (input, intermediate and output matching circuits), and two drain bias circuits. High dielectric constant material SrTiO3 (STO) is used for by-pass and input coupling capacitors. Very small die size of 0.77 mm2 has been realized by using the STO capacitors and negative feedback circuit technology. High 1 dB output gain compression point (P1dB) of 13 dBm, high gain of 21.4 dB and low dissipation current of 41.3 mA have been achieved under 3.0 V single-supply condition.