Abstract: This paper presents a low-voltage low-power variable gain amplifier,which is applied in the automatic gain control loop of a super heterodyne receiver.Six stages are cascaded to provide an 81dB digitally controlled gain range in a 3dB step.The gain step error is less than 05dB.It operates at an intermediate frequency of 300kHz,and the power consumption is 1.35mW from a 1.8V supply.The prototype chip is implemented in a TSMC’s 0.18μm 1P6M CMOS process and occupies approximately 0.24mm2.It is very suitable for portable wireless communication systems.The measurement results agree well with the system requirements.

Key words: variable gain amplifier, low voltage, low power, super heterodyne receiver, CMOS RF integrated circuits