Patent ID: 7268636
Filing Date: 2007-09-11
Classification: H03B,H03K,H03L

Abstract:
1. A voltage controlled oscillator having an amplifier, a feedback circuit and a crystal oscillator, said feedback circuit and said crystal oscillator connected in parallel across an input side terminal and an output side terminal of the amplifier, said voltage controlled oscillator comprising: a pair of first and second MOS transistors serving as variable capacitance elements for frequency adjustment; drains of the first and second MOS transistors being respectively connected to two terminals of the crystal oscillator; sources of the first and second MOS transistors being made common by directly connecting to each other; and gates of the first and second MOS transistors being made common by connecting to each other, wherein an added voltage signal of a temperature compensating signal voltage and an external frequency control signal voltage is applied to the common gate terminals of the first and second MOS transistors to thereby perform the frequency control of the oscillator.