A 2-bit adaptive analog-to-digital converter is designed using SMIC\'s 0.18 μm CMOS process.A new 2-bit structure and a current tunable charge pump are used.Thus, it can almost completely suppress the continuous wave and improve its conversion gain in Gaussian noise environment,and suppress interferences with different amplitude.Simulation results show that the converter has achieved an input dynamic range of 50 dB and a sampling bandwidth of 20 MHz,which meets the specification of GPS.The circuit has been used in a BPSK modulated direct GPS receiver.