| 摘要 |
<P>PROBLEM TO BE SOLVED: To solve the problem that a PLL circuit having a voltage-controlled oscillator becomes susceptible to the influence of noise from the outside because reduction in power source voltage narrows a variable range of a frequency control voltage. <P>SOLUTION: This PLL circuit is provided with a differential control signal generator 2 for outputting three differential control signals, and a voltage-controlled oscillator for changing an oscillation frequency according to the differential control signals outputted from the section 2 to output a local oscillation signal fo. The voltage-controlled oscillator 1 includes variable capacitance circuits 115, 116 and 117 for varying capacitive values corresponding to potential differences ΔA, ΔB and ΔC in differential control signals to be inputted, an inductor 101 connected in parallel to the variable capacitance circuits, and a negative resistance circuit 100 connected in parallel to the variable capacitance circuits and the inductor 101. The potential differences ΔA, ΔB and ΔC have intervals of Vd. <P>COPYRIGHT: (C)2005,JPO&NCIPI |
