Abstract: To provide a voltage controlled variable capacitor which can change a capacitance value thereof in a wide controlled voltage range and control the capacitance value easily with a high precision without complicating the circuit configuration thereof, and to provide a voltage controlled variable capacitor which can change a capacitance value thereof with a good linearity. The voltage controlled varactor is configured in a manner that varactors VCk, each formed by a series connection of a fixed capacitor Ck (k=1, 2, . . . , n) and a MOS transistor Mk of N channel type, are connected in parallel. The MOS transistors M1 to Mn are configured in a manner that gate widths W are same but gate lengths L1 to Ln are elongated sequentially (that is, L1<L2< . . . <Ln) so that the threshold voltages thereof are differentiated from one another.

Abstract: With first, second and third current exchanger circuits cascaded, a current in proportion to a difference between an ambient temperature Ta and a reference temperature Tr is input to the first current exchanger circuit. The first current exchanger circuit supplies a current in proportion to the square of Ta?Tr to the second current exchanger circuit, the second current exchanger circuit supplies a current in proportion to the fourth power of Ta?Tr to the third current exchanger circuit, and the third current exchanger circuit outputs a current in proportion to the fifth power of Ta?Tr. Each of the first, second and third current exchanger circuits has a configuration which does not require a high supply voltage enough to drive a series circuit of three or more diodes.

Abstract: To provide a voltage controlled variable capacitor which can change a capacitance value thereof in a wide controlled voltage range and control the capacitance value easily with a high precision without complicating the circuit configuration thereof, and to provide a voltage controlled variable capacitor which can change a capacitance value thereof with a good linearity. The voltage controlled varactor is configured in a manner that varactors VCk, each formed by a series connection of a fixed capacitor Ck (k=1, 2, - - - , n) and a MOS transistor Mk of N channel type, are connected in parallel. The MOS transistors M1 to Mn are configured in a manner that gate widths W are same but gate lengths L1 to Ln are elongated sequentially (that is, L1<L2< - - - <Ln) so that the threshold voltages thereof are differentiated from one another.

Abstract: With first, second and third current exchanger circuits cascaded, a current in proportion to a difference between an ambient temperature Ta and a reference temperature Tr is input to the first current exchanger circuit. The first current exchanger circuit supplies a current in proportion to the square of Ta−Tr to the second current exchanger circuit, the second current exchanger circuit supplies a current in proportion to the fourth power of Ta−Tr to the third current exchanger circuit, and the third current exchanger circuit outputs a current in proportion to the fifth power of Ta−Tr. Each of the first, second and third current exchanger circuits has a configuration which does not require a high supply voltage enough to drive a series circuit of three or more diodes.