Tuning circuit and receiver

Claim 1

A tuning circuit comprising: a current-controlled variable inductor including a tuning coil having two ends, and a control coil for adjusting magnetic flux density of said tuning coil by controlling a control current flowing through said control coil, said control coil being provided in proximity to said tuning coil, thereby controlling inductance value of said tuning coil; a first tuning capacitor of a fixed type connected between one end of said tuning coil connected in series with an antenna and ground; a second tuning capacitor of a fixed type connected between the other end of said tuning coil outputting a receiving frequency and ground; and means for selecting a desired tuning frequency by changing tuning frequency of an antenna tuning circuit including said tuning coil and said first and second tuning capacitors, by supplying said control current to said control coil wherein current supplied to said control coil is controlled by means of a control current supply circuit, thereby controlling the tuning frequency of said tuning circuit, said control current supply circuit being constructed in such a manner that said control coil for adjusting the inductance value of said tuning coil by controlling the magnetic flux density thereof is connected at one end thereof to a connection point between the emitter of a first transistor and the collector of a second transistor; the other end of said control coil is connected to a connection point between the emitter of a third transistor and the collector of a fourth transistor; said first and said third transistor have their collectors connected to a first reference voltage source; and said second and said fourth transistor have their emitters connected to a ground terminal.