Electronic apparatus with two quartz crystal oscillators utilizing different vibration modes

• US 6,897,743 B2
• Filed: 03/04/2003
• Issued: 05/24/2005
• Est. Priority Date: 03/06/2002
• Status: Expired due to Fees

• Current Assignee: Piedek Technical Laboratory
• Original Assignee: Piedek Technical Laboratory
• Inventors: Kawashima, Hirofumi
• Primary Examiner(s): Summons, Barbara
• Application Number:
  US10/378,724
• Publication Number:
  US 20030169130A1
• Time in Patent Office: 812 Days
• Field of Search: 333/200, 333/186, 333/187, 331/107.A, 331/156, 310/370
• US Class Current: 333/187
• CPC Class Codes: H03H 2003/026 the resonators or networks being of the tuning fork type
• CPC Class Codes: H03H 2003/0492 during the manufacture of a tuning-fork
• CPC Class Codes: H03H 9/0547 consisting of a vertical arrangement H03H9/0566 takes precedence
• CPC Class Codes: H03H 9/1021 the BAW device being of the cantilever type
• CPC Class Codes: H03H 9/215 consisting of quartz

Abstract

An electronic apparatus has a display portion and quartz crystal oscillators having different modes of vibration. Each of the quartz crystal oscillators has a quartz crystal oscillating circuit having a quartz crystal resonator. The quartz crystal resonator of one of the quartz crystal oscillating circuits is a width-extensional mode quartz crystal resonator capable of vibrating in a width-extensional mode. The width-extensional mode quartz crystal resonator has a vibrational portion, connecting portions disposed at ends of the vibrational portion, supporting portions connected to the vibrational portion through the connecting portions, and electrodes disposed on upper and lower surfaces of the vibrational portion. The quartz crystal oscillating circuit having the width-extensional mode quartz crystal resonator outputs a clock signal for operating the electronic apparatus to display time information at the display portion.

Claims

1. An electronic apparatus comprising:

a display portion; and

first and second quartz crystal oscillators comprised of first and second quartz crystal oscillating circuits each having a quartz crystal resonator, an amplifier, a plurality of resistors, and a plurality of capacitors, a mode of vibration of the quartz crystal resonator of the first quartz crystal oscillating circuit being different from that of the quartz crystal resonator of the second quartz crystal oscillating circuit;

wherein the quartz crystal resonator of one of the first and second quartz crystal oscillating circuits comprises a quartz crystal tuning fork resonator capable of vibrating in a flexural mode of an inverse phase and having a fundamental mode of vibration and a second overtone mode of vibration, the quartz crystal tuning fork resonator being electrically connected to an amplification circuit having an amplifier 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, and the quartz crystal tuning fork resonator having a quartz crystal tuning fork base, a plurality of quartz crystal tuning fork tines connected to the quartz crystal tuning fork base, and a groove having stepped portions formed in at least one of opposite main surfaces of each of the quartz crystal tuning fork tines;

wherein a merit value M₁ of the fundamental mode of vibration of the quartz crystal tuning fork resonator is greater than a merit value M₂ of the second overtone mode of vibration thereof so the second overtone mode of vibration thereof is suppressed and a high frequency stability for the fundamental mode vibration thereof is obtained, 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;

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 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; and

wherein an output signal of the quartz crystal oscillating circuit comprising the quartz crystal tuning fork resonator is a clock signal for operation of the electronic apparatus to display time information at the display portion, the clock signal having an oscillation frequency of the fundamental mode of vibration of the quartz crystal tuning fork resonator.

2. An electronic apparatus according to claim 1;

wherein the oscillation frequency of the fundamental mode of vibration of the quartz crystal tuning fork resonator is within a range of 10 kHz to 200 kHz.

3. An electronic apparatus according to claim 2;

wherein the groove formed in at least one of the opposite main surfaces of each of the quartz crystal tuning fork tines has a width W₂ and a base portion having a thickness t₁; and

wherein a ratio W₂/W is greater than 0.35 and less than 1, and a ratio t₁/t is less than 0.79, where W and t represent a width and a thickness, respectively, of each of the quartz crystal tuning fork tines.

4. An electronic apparatus according to claim 3;

wherein the thickness t₁ of the base portion of the groove is zero to define a through-hole extending between the opposite main surfaces of each of the quartz crystal tuning fork tines.

5. An electronic apparatus according to claim 3;

wherein the opposite main surfaces of the quartz crystal tuning fork tines comprise first and second opposite main surfaces each having a central linear portion, the groove being formed in the central linear portion of one of the first and second main surfaces of each of the quartz crystal tuning fork tines and having the width W₂ which is greater than or equal to a distance W₁ extending between a first side of the groove and a first side of the quartz crystal tuning fork tine and is greater than or equal to a distance W₃ extending between a second side of the groove opposite the first side thereof and a second side of the quartz crystal tuning fork tine opposite the first side thereof, the distance W₁ being greater than, equal to, or less than the distance W₃.

6. An electronic apparatus according to claim 5;

wherein the groove has a length l₁; and

wherein a ratio l₁/l is within a range of 0.2 to 0.78, where l represents an overall length of the quartz crystal tuning fork resonator.

7. An electronic apparatus according to claim 2;

wherein the amplifier of the amplification circuit comprises a CMOS inverter.

8. An electronic apparatus according to claim 7;

wherein the quartz crystal resonator of one of the first and second quartz crystal oscillating circuits comprises a width-extensional mode quartz crystal resonator capable of vibrating in a width-extensional mode.

9. An electronic apparatus according to claim 7;

wherein the quartz crystal resonator of one of the first and second quartz crystal oscillating circuits comprises a thickness shear mode quartz crystal resonator capable of vibrating in a thickness shear mode.

10. An electronic apparatus comprising:

a display portion; and

first and second quartz crystal oscillators comprised of first and second quartz crystal oscillating circuits each having a quartz crystal resonator, an amplifier, a plurality of resistors, and a plurality of capacitors, a mode of vibration of the quartz crystal resonator of the first quartz crystal oscillating circuit being different from that of the quartz crystal resonator of the second quartz crystal oscillating circuit;

wherein the quartz crystal resonator of one of the first and second quartz crystal oscillating circuits comprises a quartz crystal tuning fork resonator capable of vibrating in a flexural mode of an inverse phase and having a fundamental mode of vibration and a second overtone mode of vibration, the quartz crystal tuning fork resonator being electrically connected to an amplification circuit having an amplifier 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, and the quartz crystal tuning fork resonator having a quartz crystal tuning fork base, a plurality of quartz crystal tuning fork tines connected to the quartz crystal tuning fork base, and a groove having stepped portions formed in at least one of opposite main surfaces of each of the quartz crystal tuning fork tines;

wherein a merit value M₁ of the fundamental mode of vibration of the quartz crystal tuning fork resonator is greater than a merit value M₂ of the second overtone mode of vibration thereof so the second overtone mode of vibration thereof is suppressed and a high frequency stability for the fundamental mode vibration thereof is obtained, 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;

wherein a ratio of an amplification rate α

₁ of the fundamental mode of vibration and an amplification rate α

₂ of the second overtone mode of vibration of the amplification circuit is greater than a ratio of a feedback rate β

₂ of the second overtone mode of vibration and a feedback rate β

₁ of the fundamental mode of vibration of the feedback circuit, a product of the amplification rate α

₁ and the feedback rate β

₁ of the fundamental mode of vibration being greater than 1; and

wherein an output signal of the quartz crystal oscillating circuit comprising the quartz crystal tuning fork resonator is a clock signal for operation of the electronic apparatus to display time information at the display portion, the clock signal having an oscillation frequency of the fundamental mode of vibration of the quartz crystal tuning fork resonator.

11. An electronic apparatus according to claim 10;

wherein the output signal of the quartz crystal oscillating circuit comprising the quartz crystal tuning fork resonator is outputted through a buffer circuit; and

wherein the oscillation frequency of the fundamental mode of vibration of the quartz crystal tuning fork resonator is within a range of 10 kHz to 200 kHz.

12. An electronic apparatus according to claim 11;

wherein the amplifier of the amplification circuit comprises a CMOS inverter.

13. An electronic apparatus according to claim 12;

wherein a width W₂ of the groove formed in at least one of the opposite main surfaces of each of the quartz crystal tuning fork tines is within a range of 0.03 mm to 0.12 mm; and

wherein a ratio W₂/W is greater than 0.35 and less than 1, where W represents a width of each of the quartz crystal tuning fork tines.

14. An electronic apparatus according to claim 13;

wherein a ratio t₁/t is less than 0.79, where t₁ is a thickness of a base portion of the groove formed in at least one of the opposite main surfaces of each of the quartz crystal tuning fork tines and t is a thickness of each of the quartz crystal tuning fork tines; and

wherein the thickness t₁ is zero to define a through-hole extending between the opposite main surfaces of each of the quartz crystal tuning fork tines.

15. An electronic apparatus according to claim 13;

wherein the quartz crystal resonator of one of the first and second quartz crystal oscillating circuits comprises a thickness shear mode quartz crystal resonator capable of vibrating in a thickness shear mode.

16. An electronic apparatus according to claim 12;

wherein the merit value M₂ for the second overtone mode of vibration of the quartz crystal tuning fork resonator is less than 30.

17. An electronic apparatus according to claim 12;

wherein a stable factor S₁ of the fundamental mode of vibration of the quartz crystal tuning fork resonator and a stable factor S₂ of the second overtone mode of vibration thereof are defined by r₁/2Q₁² and r₂/2Q₂², respectively; and

wherein S₁ is less than S₂.

18. An electronic apparatus according to claim 12;

wherein a series resistance R₁ of the fundamental mode of vibration of the quartz crystal tuning fork resonator is less than a series resistance R₂ of the second overtone mode of vibration thereof; and

wherein a capacitance ratio r₁ of the fundamental mode of vibration of the quartz crystal tuning fork resonator is less than a capacitance ratio r₂ of the second overtone mode of vibration thereof.

19. An electronic apparatus according to claim 12;

wherein the feedback circuit comprises a capacitor of a gate side having a capacitance C_g and a capacitor of a drain side having a capacitance C_d; and

wherein a load capacitance C_L of the capacitors is less than 18 pF, where C_L is defined by C_gC_d/(C_g+C_d).

20. An electronic apparatus comprising:

a display portion; and

first and second quartz crystal oscillators comprised of first and second quartz crystal oscillating circuits, respectively, each having a quartz crystal resonator, an amplifier, a plurality of resistors, and a plurality of capacitors, a mode of vibration of the quartz crystal resonator of the first quartz crystal oscillating circuit being different from that of the quartz crystal resonator of the second quartz crystal oscillating circuit;

wherein the quartz crystal resonator of one of the first and second quartz crystal oscillating circuits comprises a width-extensional mode quartz crystal resonator capable of vibrating in a width-extensional mode and having a piezoelectric constant e₁₂ within a range of 0.095 C/m² to 0.18 C/m² in the absolute value, the width-extensional mode quartz crystal resonator having a vibrational portion having a length greater than a width thereof and a thickness smaller than the width, connecting portions disposed at ends of the vibrational portion, supporting portions connected to the vibrational portion through the connecting portions, and electrodes disposed on upper and lower faces of the vibrational portion; and

wherein an output signal of the quartz crystal oscillating circuit comprising the width-extensional mode quartz crystal resonator is a clock signal outputted through a buffer circuit and for operation of the electronic apparatus to display time information at the display portion.

21. An electronic apparatus according to claim 20;

a cutting angle of the width-extensional mode quartz crystal resonator is within a range of XZtw(−

25°

-+25°

)/(−

30°

-+30°

).

22. An electronic apparatus according to claim 20;

a cutting angle of the width-extensional mode quartz crystal resonator is within a range of XZt(−

12-−

13.5°

) or XZt(−

18.5°

-−

9.8°

) or XZtw(−

13°

-−

18°

)/±

(+0.5°

-+30°

).

23. An electronic apparatus according to claim 20;

wherein quartz crystal oscillating circuit having the width-extensional mode quartz crystal resonator has a CMOS inverter, a feedback resistor, a drain resistor, a capacitor of a gate side, and a capacitor of a drain side.

24. An electronic apparatus comprising:

a display portion; and

first and second quartz crystal oscillators comprised of first and second quartz crystal oscillating circuits each having a quartz crystal resonator, an amplifier, a plurality of resistors, and a plurality of capacitors, a mode of vibration of the quartz crystal resonator of the first quartz crystal oscillating circuit being different from that of the quartz crystal resonator of the second quartz crystal oscillating circuit;

wherein the quartz crystal resonator of one of the first and second quartz crystal oscillating circuits comprises a quartz crystal tuning fork resonator capable of vibrating in a flexural mode of an inverse phase and having a fundamental mode of vibration and a second overtone mode of vibration, the quartz crystal tuning fork resonator being electrically connected to an amplification circuit having an amplifier 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, and the quartz crystal tuning fork resonator having a quartz crystal tuning fork base, a plurality of quartz crystal tuning fork tines connected to the quartz crystal tuning fork base, and a groove having stepped portions formed in a central linear portion of at least one of opposite main surfaces of each of the quartz crystal tuning fork tines so that a width of the groove is greater than or equal to a distance in the width direction of the groove measured from an outer edge of the groove to an outer edge of the quartz crystal tuning fork tine in which the groove is formed;

wherein a merit value M₁ of the fundamental mode of vibration of the quartz crystal tuning fork resonator is greater than a merit value M₂ of the second overtone mode of vibration thereof so the second overtone mode of vibration thereof is suppressed and a high frequency stability for the fundamental mode vibration thereof is obtained, 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;

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 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; and

wherein an output signal of the quartz crystal oscillating circuit comprising the quartz crystal tuning fork resonator is a clock signal for operation of the electronic apparatus to display time information at the display portion, the clock signal having an oscillation frequency of the fundamental mode of vibration of the quartz crystal tuning fork resonator.

25. An electronic apparatus according to claim 24;

wherein a spaced-apart distance between the quartz crystal tuning fork tines is within a range of 0.05 mm to 0.35 mm and is greater than or equal to a width of the groove formed in at least one of the opposite main surfaces of each of the quartz crystal tuning fork tines.

26. An electronic apparatus according to claim 24;

wherein a length of the groove formed in the central linear portion of one of the opposite main surfaces of each of the quartz crystal tuning fork tines is within a range of 40% to 80% of a length of each of the quartz crystal tuning fork tines.

27. An electronic apparatus according to claim 24;

wherein the merit value M₂ for the second overtone mode of vibration of the quartz crystal tuning fork resonator is less than 30.

28. An electronic apparatus according to claim 24;

wherein the quartz crystal tuning fork tines comprise a first quartz crystal tuning fork tine and a second quartz crystal tuning fork tine, the groove being formed in each of the opposite main surfaces of each of the first and second quartz crystal tuning fork tines and disposed opposite each other in a thickness direction of the first and second quartz crystal tuning fork tines.

29. An electronic apparatus according to claim 28;

wherein each of the first and second quartz crystal tuning fork tines has a side surface comprising an outer side surface; and

further comprising a plurality of first electrodes disposed in the grooves of the first and second quartz crystal tuning fork tines and a plurality of second electrodes disposed on the outer side surfaces of the first and second quartz crystal tuning fork tines, the second electrodes of each of the first and second quartz crystal tuning fork tines having an electrical polarity opposite to an electrical polarity of the first electrodes of each of the first and second quartz crystal tuning fork tines.

30. An electronic apparatus according to claim 29;

wherein the first electrodes disposed in the grooves of the first quartz crystal tuning fork tine are connected to the second electrode disposed on the outer side surface of the second quartz crystal tuning fork tine so that the first electrodes of the first quartz crystal tuning fork tine and the second electrode of the second quartz crystal tuning fork tine define a first electrode terminal; and

wherein the second electrode disposed on the outer side surface of the first quartz crystal tuning fork tine is connected to the first electrodes disposed in the grooves of the second quartz crystal tuning fork tine so that the second electrode of the first quartz crystal tuning fork tine and the first electrodes of the second quartz crystal tuning fork tine define a second electrode terminal.

31. An electronic apparatus according to claim 30;

wherein when a direct current voltage is applied between the first and second electrode terminals, a direction of an outer electric field generated between the second electrode disposed on the outer side surface of the first quartz crystal tuning fork tine and the first electrode disposed in one of the grooves opposite to the second electrode disposed on the outer side surface of the first quartz crystal tuning fork tine is the same as a direction of an outer electric field generated between the second electrode disposed on the outer side surface of the second quartz crystal tuning fork tine and the first electrode disposed in one of the grooves opposite to the second electrode disposed on the outer side surface of the second quartz crystal tuning fork tine; and

wherein the directions of the outer electric fields of the first and second quartz crystal tuning fork tines are generally along an x-axis direction of the quartz crystal tuning fork resonator.

32. An electronic apparatus according to claim 31;

wherein no electric field is generated between first electrodes disposed in opposite grooves of the first and second quartz crystal tuning fork tines when a direct current voltage is applied between the first electrodes disposed in the opposite grooves.

33. An electronic apparatus comprising:

a display portion; and

a pair of quartz crystal oscillators each comprised of a quartz crystal oscillating circuit having a quartz crystal resonator, an amplifier, a plurality of resistors, and a plurality of capacitors, a mode of vibration of the quartz crystal resonator of each of the quartz crystal oscillating circuits being different from one another;

wherein the quartz crystal resonator of one of the quartz crystal oscillating circuits comprises a quartz crystal tuning fork resonator capable of vibrating in a flexural mode of an inverse phase and having a fundamental mode of vibration and a second overtone mode of vibration, the quartz crystal tuning fork resonator being electrically connected to an amplification circuit having a CMOS inverter and a feedback resistor and electrically connected to capacitors and a drain resistor of a feedback circuit having the quartz crystal tuning fork resonator, and the quartz crystal tuning fork resonator having 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 length greater than each of a width and a thickness thereof;

wherein a merit value M₁ of the fundamental mode of vibration of the quartz crystal tuning fork resonator is greater than a merit value M₂ of the second overtone 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;

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 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; and

wherein an output signal of the quartz crystal oscillating circuit comprising the quartz crystal tuning fork resonator is a clock signal for use in operation of the electronic apparatus to display time information at the display portion, the clock signal having an oscillation frequency of the fundamental mode of vibration of the quartz crystal tuning fork resonator.

34. An electronic apparatus according to claim 33;

wherein one of the quartz crystal oscillators comprises a quartz crystal oscillating circuit having a thickness shear mode quartz crystal resonator capable of vibrating in a thickness shear mode.

35. An electronic apparatus according to claim 34;

wherein a ratio of an amplification rate α

₁ of the fundamental mode of vibration and an amplification rate α

₂ of the second overtone mode of vibration of the amplification circuit is greater than a ratio of a feedback rate β

₂ of the second overtone mode of vibration and a feedback rate β

₁ of the fundamental mode of vibration of the feedback circuit, a product of the amplification rate α

₁ and the feedback rate β

₁ of the fundamental mode of vibration being greater than 1.

36. An electronic apparatus according to claim 35;

wherein the 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.

37. An electronic apparatus according to claim 35;

wherein the quartz crystal tuning fork tines comprise a first quartz crystal tuning fork tine and a second quartz crystal tuning fork tine; and

wherein a first electrode is disposed on each of side surfaces of the first quartz crystal tuning fork tine and a second electrode is disposed on each of side surfaces of the second quartz crystal tuning fork tine so that an electrical polarity of the first electrode is opposite to an electrical polarity of the second electrode.

38. An electronic apparatus according to claim 37;

wherein a spaced-apart distance between the quartz crystal tuning fork tines is within a range of 0.05 mm to 0.35 nm; and

wherein the merit value M₁ for the fundamental mode of vibration of the quartz crystal tuning fork resonator is greater than 65 so that a high frequency stability for the fundamental mode of vibration thereof is obtained.

39. An electronic apparatus according to claim 38;

wherein a groove having stepped portions is formed in a central linear portion of at least one of opposite main surfaces of each of the quartz crystal tuning fork tines so that a width of the groove is greater than or equal to a distance in the width direction of the groove measured from an outer edge of the groove to an outer edge of the quartz crystal tuning fork tine in which the groove is formed; and

wherein the spaced-apart distance between the quartz crystal tuning fork tines is greater than or equal to the width of the groove formed in at least one of the opposite main surfaces of each of the quartz crystal tuning fork tines.

40. An electronic apparatus comprising:

a display portion; and

at least one quartz crystal oscillating circuit comprised of a quartz crystal tuning fork resonator capable of vibrating in a flexural mode of an inverse phase and having a fundamental mode of vibration and 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 length greater than each of a width and a thickness thereof, the quartz crystal tuning fork resonator being electrically connected to an amplification circuit having a CMOS inverter and a feedback resistor and electrically connected to capacitors and a drain resistor of a feedback circuit having the quartz crystal tuning fork resonator, a series resistance R₁ of the fundamental mode of vibration of the quartz crystal tuning fork resonator being less than a series resistance R₂ of the second overtone mode of vibration thereof;

wherein a merit value M₁ of the fundamental mode of vibration of the quartz crystal tuning fork resonator is greater than a merit value M₂ of the second overtone 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;

wherein a ratio of an amplification rate α

₁ of the fundamental mode of vibration and an amplification rate α

₂ of the second overtone mode of vibration of the amplification circuit is greater than a ratio of a feedback rate β

₂ of the second overtone mode of vibration and a feedback rate β

₁ of the fundamental mode of vibration of the feedback circuit, a product of the amplification rate α

₁ and the feedback rate β

₁ of the fundamental mode of vibration being greater than 1; and

wherein an output signal of the quartz crystal oscillating circuit comprising the quartz crystal tuning fork resonator is a clock signal for use in operation of the electronic apparatus to display time information at the display portion, the clock signal having an oscillation frequency of the fundamental mode of vibration of the quartz crystal tuning fork resonator.

41. An electronic apparatus according to claim 40;

wherein the at least one quartz crystal oscillating circuit comprises a plurality of quartz crystal oscillating circuits each having a quartz crystal resonator, an amplifier, a plurality of resistors, and a plurality of capacitors, at least two of the quartz crystal oscillating circuits vibrating in different vibrational modes; and

wherein one of the quartz crystal oscillating circuits comprises a thickness shear mode quartz crystal resonator capable of vibrating in a thickness shear mode.

42. An electronic apparatus according to claim 40;

wherein the quartz crystal tuning fork tines comprise a first quartz crystal tuning fork tine and a second quartz crystal tuning fork tine spaced-apart from the first quartz crystal tuning fork tine at a distance within a range of 0.05 mm to 0.35 mm; and

wherein a first electrode is disposed on one of side surfaces of the first quartz crystal tuning fork tine and a second electrode is disposed on one of side surfaces of the second quartz crystal tuning fork tine so that the first electrode has an electrical polarity opposite to an electrical polarity of the second electrode.

43. An electronic apparatus according to claim 42;

wherein the 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; and

wherein the output signal of the quartz crystal oscillating circuit is outputted through a buffer circuit and has an oscillation frequency of about 32.768 kHz with a frequency deviation within a range of −

100 PPM to +100 PPM.