;Both C-band and X-band fully integrated power amplifiers (PA) are designed in this thesis, which are fabricated in WINTM 0.25-µm GaN pHEMT and tsmcTM 0.18-µm CMOS Processes. A PA with wideband, high gain and high linearity adopted differential Guanella-type transmission-line transformers (DTLTs) and T-type transmission-line matching is designed to achieve broadband and low loss, and adopted power combine to enhance output power. The capacitive neutralization technique is adopted to mitigate the Miller effect to improve power gain and enhance stability. The linearity at back-off region is enhanced by predistortion technique. High gain and high linearity of the broadband amplifier are thus implemented. The measurement results of the first PA shows a power gain of 16.2 dB, a saturated output power of 25.3 dBm, an output 1-dB gain compression point of 24.8 dBm. The 3-dB bandwidth is from 4.6 to 11.3 GHz, and the fractional bandwidth is 84.3 %. The chip size is 3.3 (2.075×1.587) mm2. The second PA achieves a power gain of 25.2 dB, a saturated output power of 21.9 dBm, a maximum power added efficiency of 19.3 %, an output 1-dB gain compression point of 17.2 dBm with power added efficiency of 17.2 %. The 3-dB bandwidth is from 4.6 to 12.4 GHz. The 3-dB bandwidth of saturation power is from 5.5 to 10.5 GHz. The chip area is 1.95×0.81 mm2.