Quartz crystal unit, and quartz crystal oscillator having quartz crystal unit

A quartz crystal oscillator comprising:

• at least one quartz crystal tuning fork resonator capable of vibrating in a flexural mode of an inverse phase and having a fundamental mode of vibration, a second overtone mode of vibration, a quartz crystal tuning fork base, and a plurality of quartz crystal tuning fork tines connected to the quartz crystal tuning fork base, the quartz crystal tuning fork resonator being electrically connected to an amplification circuit having a CMO inverter and a feedback resistor and to a plurality of capacitors and a drain resistor of a feedback circuit having the quartz crystal tuning fork resonator;
• wherein a merit value M2 for the second overtone mode of vibration of the quartz crystal tuning fork resonator is less than a merit value M1 for the fundamental mode of vibration thereof, the merit values M1 and M2 being defined by the ratios Q1/r1 and Q2/r2, respectively, where Q1 and Q2 represent a quality factor of the fundamental mode of vibration and the second overtone mode of vibration, respectively, of the quartz crystal tuning fork resonator and r1 and r2 represent a capacitance ratio of the fundamental mode of vibration and the second overtone mode of vibration, respectively, of the quartz crystal tuning fork resonator;
• and
• wherein a ratio of an absolute value of negative resistance −RL1 of the fundamental mode of vibration of the amplification circuit and a series resistance R1 of the fundamental mode of vibration of the quartz crystal tuning fork resonator is greater than that of an absolute value of negative resistance −RL2 of the second overtone mode of vibration of the amplification circuit and a series resistance R2 of the second overtone mode of vibration thereof.

A quartz crystal unit comprising:

• a quartz crystal tuning fork resonator capable of vibrating in a flexural mode of an inverse phase and having a fundamental mode of vibration, a second overtone mode of vibration, a quartz crystal tuning fork base, and a plurality of quartz crystal tuning fork tines connected to the quartz crystal tuning fork base, each of the quartz crystal tuning fork tines having a first main surface and a second main surface opposite the first main surface;
• a case having an interior space for housing the quartz crystal tuning fork resonator and an open end communicating with the interior space;
• and
• a lid for covering the open end of the case;
• wherein a merit value M2 for the second overtone mode of vibration of the quartz crystal tuning fork resonator is less than 30 so that the second overtone mode of vibration thereof is suppressed, the merit value M2 being defined by a ratio Q2/r2, where Q2 and r2 represent a quality factor and a capacitance ratio of the second overtone mode of vibration, respectively, of the quartz crystal tuning fork resonator capable of vibrating in the second overtone mode.