Abstract: A digital-controlled programmable gain amplifier(PGA) is designed for the RF front-end circuits of large scale wireless sensor network. Five serial stages are employed in the PGA and Each stage is composed of a programmable attenuator followed by a fixed-gain amplifier that has the function of DC-offset rejection. Variable gain is achieved via two steps. The 6dB gain steps are implemented using the R-2R ladder network and the 0.75dB gain step is implemented by a series ladder linear attenuator. Simulation results show that the PGA provide a 78dB gain control range with 0.75dB step and the overall gain accuracy was 0.7mdB. The OIP3 is 16.1dBm. The PGA is fabricated in 0.18μm 1P6M CMOS process and occupies 0.08mm² active area.