Disclosed herein is an automatic gain control circuit including a power
detector. The automatic gain control circuit includes a receiving unit
for receiving an RF signal and a gain control unit for controlling the
gain of the receiving unit. The receiving unit comprises an amplification
part including a low noise amplifier and a gain amplifier for amplifying
the RF signal, a mixer for down-converting and tuning the RF signal
output from the gain amplifier, a low pass filter for receiving the
down-converted signal from the mixer, and an intermediate frequency
variable gain amplifier for amplifying the signal filtered by the low
pass filter to an intermediate frequency signal. The gain control unit
comprises a received signal strength indicator connected to the output
port of the low pass filter to detect the level of the output signal of
the low pass filter, a first comparator for comparing the output signal
level detected by the received signal strength indicator with a reference
signal level, a power detector for detecting the output signal level of
the amplification part of the receiving unit, a second comparator for
comparing the output signal level detected by the power detector with a
reference signal level, and a gain controller for increasing, decreasing
or holding the gain in response to the signals output from the first and
second comparators.