In receiver systems for cellular phones using the W-CDMA method, the
change in DC voltage occurring when the gain of a programmable gain
amplifier (PGA circuit) is switched to adjust the gain for a received
signal, can be suppressed. A sample-and-hold circuit is installed
containing a "sample" mode for directly outputting a signal from the PGA
section and also containing a "hold" mode for outputting the electric
charge of a specified voltage stored in a capacitor. This sample-and-hold
circuit normally operates in "sample" mode so the output signal from the
PGA section is directly output, but is operated in "hold" mode at the
gain switching timing of the PGA circuit, so that the electric charge of
the specified voltage stored in the capacitor is output for a specified
length of time (equal to the time required for the DC voltage change to
converge to a stable level).