Patent ID: 6977555

Claim:
A tuner circuit comprising: an input terminal; an input tuning circuit for tuning to an RF signal of a desired channel among RF signals of a plurality of channels input from the input terminal; a variable-gain amplifier circuit for amplifying or attenuating a level of an RF signal output from the input tuning circuit to a prescribed level; a pre-amplifier circuit disposed at an upstream side of the input tuning circuit; and a variable attenuator circuit disposed at an upstream side of the pre-amplifier circuit, including a PIN diode disposed in series with a signal path of the tuner circuit, the PIN diode having characteristics between direct current and intermodulation distortion such that intermodulation distortion of a signal that flows therethrough is maximized at a desired value of a direct current; wherein the variable-gain amplifier circuit and the variable attenuator circuit are controlled according to a common AGC voltage that is set based on a level of an input RE signal, and operations of the variable-gain amplifier circuit and the variable attenuator circuit in relation to the AGC voltage are set such that when the input RF signal is at a maximum assumed level, a direct current that flows through the PIN diode is less than the predetermined value of a direct current that maximizes intermodulation distortion.