Voltage-controlled oscillator, IC chip for voltage-controlled oscillator, resistance setting apparatus, and resistance setting method

摘要

The invention aim at improving the linearity of frequency versus control voltage characteristic and to increase the range of frequency that can be varied by a control voltage. A resistor circuit (20) is connected between a piezoelectric resonator (X) and an oscillator circuit (100). The resistor circuit (20) includes a plurality of resistors (Rs1 to Rsn) and corresponding switches (SW1 to SWn). The resistor circuit (20) adjusts the amplitude of oscillation. When a control voltage (Vc) applied to a varactor (Cv) is at a low level, clipping by a forward voltage of the varactor (Cv) is suppressed, and the frequency is linearly changed by the control voltage Vc within a range of a low level to a high level.