A low-power wideband hybrid automatic gain control （AGC） loop for a GNSS receiver is presented. Single AGC in the I/Q path is composed of four-stage programmable gain amplifiers （PGAs）, a differential peak detector, two comparators, a control algorithm logic, a decoder and the reference voltage source. Besides being controlled by an AGC loop, the gain of PGAs could altematively be controlled by an off-chip digital baseband processor through the SPI interface. To obtain low power consumption and noise, an improved source degenerated amplifier is adopted, and the I/Q path phase mismatch within the ±5° range is calibrated with 0.2° accuracy. Implemented in 65 nm CMOS, the measured PGA total gains range from 9.8 to 59.5 dB with an average step of 0.95 dB and simulated bandwidth of more than 110 MHz. The settling time is about 180 μs with 80% AM input with measured signal power from -76.7 to -56.6 dBm from a radio-frequency amplifier （RFA） input port, and also reduces to 90 #s with clock frequency doubling. The single AGC consumes almost 0.8 mA current from the 2.5-V supply and occupies an area of 750 × 300 μm2.
