The invention provides a signal processing semiconductor integrated
circuit of the direct conversion system, which includes a dummy amplifier
having the same circuit configuration as a low noise amplifier being the
first stage amplifier, in which the DC offset calibrations on the
subsequent stage amplifiers are carried out during shifting into the
reception mode in a state that the low noise amplifier is deactivated and
the dummy amplifier is activated. Thereby, the invention achieves to
suppress generation of the DC offsets resulting from the leakage noises
of the local oscillator during shifting into the reception mode, and to
enhance the reception sensitivity.