Overtone crystal oscillator

摘要

An overtone crystal oscillator includes a crystal vibrator, a CMOS circuit connected in parallel to the crystal vibrator, and two load capacitors connected to the input and output of the CMOS circuit, respectively. The capacitors have respective capacitances Cg and Cd determined to satisfy at least one of following two conditions wherein the first condition is that an oscillation starting resistance RKN of a desired N-th overtone is sufficiently larger than an effective resistance RQN of the crystal vibrator of the N-th overtone, the oscillation starting resistance being expressed as: RKN=K/( omega 2xCgxCd) ( omega : oscillating frequency, K: constant determined by mutual conductance of the CMOS circuit) and the second condition is that an effective resistance RQn of the crystal vibrator of another n-th overtone except the desired N-th overtone satisfies the following relation RQn>N2xRKN/n2.