A 900-MHz bandwidth analog baseband circuit with 1-dB step and 30-dB gain dynamic range

A wide-bandwidth analog baseband circuit with digital gain control is implemented in a 65-nm CMOS process. The proposed circuit adopts a variable transconductance amplifier, which achieves constant bandwidth regardless of the gain settings. Bandwidth variation is less than ±1.2 % within the gain control range of 20 dB. The proposed analog baseband circuit has in-phase and quadrature-phase paths and draws 24.8 mA from a 1.2-V power supply. Measured results show that 1-dB step gain control with 0.25-dB differential nonlinearity (DNL) for 30-dB range and I/Q gain matching accuracy of 0.15 dB is achieved.