Electronic apparatus

Abstract

The electronic apparatus comprises a display portion and a quartz crystal oscillator at least, and said electronic apparatus comprises at least one quartz crystal oscillator. Also, the at least one oscillator comprises a quartz crystal oscillating circuit comprising an amplification circuit and a feedback circuit. The feedback circuit is constructed by a flexural mode, quartz crystal tuning fork resonator or a length-extensional mode quartz crystal resonator and for example, the quartz crystal tuning fork resonator comprising tuning fork tines and tuning fork base that are formed integrally, is shown with novel shape and electrode construction. Also, the quartz crystal tuning fork resonator, capable of vibrating in a fundamental mode and having a high frequency stability can be provided with a small series resistance and a high quality factor, even when the tuning fork resonator is miniaturized. In addition, from a relationship of an amplification rate and a feedback rate, an output signal of the quartz crystal oscillating circuit having a frequency of the fundamental mode vibration for the quartz crystal tuning fork resonator can be provided with the high frequency stability.

What is claimed is:  
     
         1 . An electronic apparatus comprising a display portion and a quartz crystal oscillator at least, said electronic apparatus having one quartz crystal oscillator, said one quartz crystal oscillator comprising: 
 a quartz crystal oscillating circuit comprising; an amplification circuit comprising an amplifier at least and a feedback circuit comprising a quartz crystal resonator and capacitors at least,    said quartz crystal resonator being a quartz crystal tuning fork resonator capable of vibrating in a flexural mode, said quartz crystal tuning fork resonator comprising: 
 tuning fork tines each of which has a length, a width and a thickness and the length greater than the width and the thickness; and  
 a tuning fork base;  
 said tuning fork tines and said tuning fork base that are formed integrally;  
 electrodes disposed facing each other on sides of said tuning fork tines so that the electrodes disposed facing each other are of opposite electrical polarity and said tuning fork tines are capable of vibrating in inverse phase,  
 and a ratio of an absolute value of negative resistance, |−RL 1 | of a fundamental mode vibration of said amplification circuit and series resistance R 1  of the fundamental mode vibration being larger than that of an absolute value of negative resistance, |−RL 2 | of a second overtone mode vibration of said amplification circuit and series resistance R 2  of the second overtone mode vibration, wherein said quartz crystal oscillating circuit comprises said quartz crystal tuning fork resonator whose figure of merit M 1  of the fundamental mode vibration is larger than figure of merit M 2  of the second overtone mode vibration to suppress the second overtone mode vibration and to get a high frequency stability for the fundamental mode vibration, and a ratio of an amplification rate α 1  for the fundamental mode vibration and an amplification rate α 2  for the second overtone mode vibration of said amplification circuit is larger than that of a feedback rate β 2  of the second overtone mode vibration and a feedback rate β 1  of the fundamental mode vibration of said feedback circuit and a product of the amplification rate α 1  and the feedback rate β 1  of the fundamental mode vibration is larger than 1,  
 and wherein an output signal of said quartz crystal oscillating circuit comprising said quartz crystal tuning fork resonator capable of vibrating in the flexural mode has a frequency of the fundamental mode vibration of said resonator and is outputted through a buffer circuit, and said output signal is a clock signal which is used to display time at said display portion of said electronic apparatus.  
   
     
     
         2 . The electronic apparatus according to  claim 1 , wherein said frequency of the fundamental mode vibration is within a range of 10 kHz to 200 kHz.  
     
     
         3 . The electronic apparatus according to  claim 2 , wherein said amplification circuit comprises a CMOS inverter and a feedback resistor, and said feedback circuit comprises said quartz crystal tuning fork resonator, a drain resistor, a capacitor of a gate side and a capacitor of a drain side.  
     
     
         4 . The electronic apparatus according to  claim 3 , wherein capacitance ratio r 1  of the fundamental mode vibration of said resonator is smaller than capacitance ratio r 2  of the second overtone mode vibration.  
     
     
         5 . The electronic apparatus according to  claim 4 , wherein S 1  is less than S 2  when stable factors of frequency S 1  and S 2  of the fundamental mode vibration and the second overtone mode vibration of said resonator are given by S 1 =r 1 /2Q 1   2  and S 2 =r 2 /2Q 2   2 , respectively.  
     
     
         6 . The electronic apparatus according to  claim 5 , wherein a tuning fork base of said resonator has cut portions.  
     
     
         7 . The electronic apparatus according to  claim 5 , wherein said quartz crystal oscillating circuit has load capacitance C L  less than 18 pF.  
     
     
         8 . The electronic apparatus according to  claim 5 , wherein series resistance R 1  of the fundamental mode vibration of said resonator is less than series resistance R 2  of the second overtone mode vibration.  
     
     
         9 . The electronic apparatus according to  claim 8 , wherein a ratio of groove width W 2  and tine width W is larger than 0.35 and less than 1, and a ratio of groove thickness t 1  and tine thickness t is less than 0.79.  
     
     
         10 . An electronic apparatus comprising a display portion and a quartz crystal oscillator at least, said electronic apparatus comprising at least one quartz crystal oscillator, said at least one quartz crystal oscillator comprising: 
 a quartz crystal oscillating circuit comprising; an amplification circuit comprising an amplifier at least and a feedback circuit comprising a quartz crystal resonator and capacitors at least,    said quartz crystal resonator being a length-extensional mode quartz crystal resonator capable of vibrating in a length-extensional mode, and said length-extensional mode quartz crystal resonator comprising: 
 a vibrational portion having a length greater than a width and a thickness smaller than the width;  
 connecting portions located at ends of said vibrational portion;  
 supporting portions connected to said vibrational portion through said connecting portions; and  
 electrodes disposed on upper and lower faces of said vibrational portion, wherein a piezoelectric constant e 12  of said resonator is within a range of 0.095 C/m 2  to 0.18 C/m 2  in the absolute value,  
 and wherein an output signal of said quartz crystal oscillating circuit comprising said length-extensional mode quartz crystal resonator is outputted through a buffer circuit, and said output signal is a clock signal which is used except time display of said electronic apparatus.  
   
     
     
         11 . The electronic apparatus according to  claim 10 , wherein a cutting angle of said resonator is within a range of XYtl(−30°-+30°)/(−40°-+40°).  
     
     
         12 . A method for manufacturing an electronic apparatus comprising a display portion and a quartz crystal oscillator at least, said electronic apparatus comprising at least one quartz crystal oscillator, said at least one quartz crystal oscillator comprising: 
 a quartz crystal oscillating circuit comprising; an amplification circuit comprising an amplifier at least and a feedback circuit comprising a quartz crystal resonator and capacitors at least,    said quartz crystal resonator being a quartz crystal tuning fork resonator capable of vibrating in a flexural mode, said quartz crystal tuning fork resonator comprising the steps of: 
 forming integrally tuning fork tines each of which has a length, a width and a thickness and the length greater than the width and the thickness and a tuning fork base;  
 disposing electrodes facing each other on sides of said tuning fork tines so that the electrodes that is disposed facing each other are of opposite electrical polarity and said tuning fork tines are capable of vibrating in inverse phase; and  
 adjusting resonance frequency of said quartz crystal tuning fork resonator after mounting it at a mounting portion by conductive adhesives or solder so that a frequency deviation is within a range of −100 PPM to +100 PPM, and said at least one quartz crystal oscillator comprising the step of: 
 constructing said quartz crystal oscillating circuit so that a ratio of an absolute value of negative resistance, |−RL 1 | of a fundamental mode vibration of said amplification circuit and series resistance R 1  of the fundamental mode vibration is larger than that of an absolute value of negative resistance, |−RL 2 | of a second overtone mode vibration of said amplification circuit and series resistance R 2  of the second overtone mode vibration, wherein said quartz crystal oscillating circuit comprises said quartz crystal tuning fork resonator whose figure of merit M 1  of the fundamental mode vibration is larger than figure of merit M 2  of the second overtone mode vibration to suppress the second overtone mode vibration and to get a high frequency stability for the fundamental mode vibration, and a ratio of an amplification rate α 1  for the fundamental mode vibration and an amplification rate α 2  for the second overtone mode vibration of said amplification circuit is larger than that of a feedback rate β 2  of the second overtone mode vibration and a feedback rate β 1  of the fundamental mode vibration of said feedback circuit and a product of the amplification rate α 1  and the feedback rate β 1  of the fundamental mode vibration is larger than 1,  
 and wherein an output signal of said quartz crystal oscillating circuit comprising said quartz crystal tuning fork resonator capable of vibrating in the flexural mode has a frequency of the fundamental mode vibration of said resonator and is outputted through a buffer circuit, and said output signal is a clock signal which is used to display time at said display portion of said electronic apparatus.  
 
   
     
     
         13 . The method of  claim 12 , wherein said amplification circuit comprises a CMOS inverter and a feedback resistor, and said feedback circuit comprises said quartz crystal tuning fork resonator, a drain resistor, a capacitor of a gate side and a capacitor of a drain side.  
     
     
         14 . The method of  claim 12 , wherein the value of |−RL 1 |/R 1  is greater than the value of 2|−RL 2 |/R 2 −1.  
     
     
         15 . The method of  claim 12 , comprising the further step of forming flexural mode, quartz crystal tuning fork resonators in a quartz crystal wafer simultaneously by at least one method of chemical, mechanical and physical methods.  
     
     
         16 . The method of  claim 15 , comprising the further steps of inspecting if there is a failure resonator or not in the quartz crystal wafer and removing the failure resonator from the quartz crystal wafer.