This paper presents the design of a Class AB power amplifier operating at a frequency band of 3.4 GHz-3.7 GHz for LTE base station applications. The proposed design is targeted for a compact, low cost, high efficiency, and good linearity features. It based on GaN HEMT CGH40006P device manufactured by Wolfspeed/Cree. The design procedure and assessment of the presented power amplifier are described in this paper. The proposed input and output matching networks with stepped tapered microstrip transmission line have enhanced the transmission coefficients of the power amplifier, resulting in improvement of overall performance. The drain voltage and current waveforms are demonstrated to ensure the appropriate biasing point of class AB. At 1dB compression, the simulated results of the proposed class AB power amplifier with one tone input signal delivers power added efficiency of 59%, and 38 dBm output power. With code division multiple access (CDMA) signal, the power amplifier delivers a 51.9% of PAE, adjacent channel power ratio (ACPR) of below than -28.5 dBc at 2.25 MHz offsets, and delivers 37 dBm (~5 W) output power.