JPS6139603A - Piezoelectric vibrator oscillating circuit - Google Patents

Abstract

PURPOSE:To improve temperature characteristic of an oscillating circuit using a vibrator by canceling temperature characteristic of the vibrator and temperature characteristic used for load capacity of the vibrator. CONSTITUTION:A capacitor 17 consists of an upper electrode 15a, a lower electrode 13 and a dielectric 14, and a capacitor 17b consists of an upper electrode 15b, a lower electrode 13 and a dielectric 14. The capacitors 17a, 17b are sealed in by a base substrate 12 and a ceramic gap 19 together with an LT piezoelectric vibrator 16. By using an LT piezoelectric vibrator having the same characteristic with the change of capacity with respect to temperature of the capacitors 17a, 17b, the temperature characteristic of the LT piezoelectric vibrator 16 can be brought close to 0ppm.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Technical Field of the Invention The present invention relates to a piezoelectric vibrator, and more particularly to a piezoelectric vibrator oscillation circuit using a piezoelectric vibrator as an oscillation circuit with improved temperature characteristics.

(2) Background of the Invention In various digital circuits, it is necessary to obtain a clock signal with an accurate frequency in order to perform stable circuit operation. Generally, oscillators used in digital circuits include a CR oscillator that uses charging and discharging of a resistor and a capacitor, a crystal oscillator that uses the natural vibration of a crystal resonator, and an oscillator that uses the vibration frequency of a piezoelectric resonator. However, it is difficult to use a CR oscillator for high frequency oscillation such as in the Mllz band, and it is also difficult to manufacture a crystal oscillator to obtain the natural frequency of the crystal resonator. Therefore, oscillators using piezoelectric vibrators are currently viewed as promising.

(3) Prior art and problems FIG. 1 is a circuit diagram of an oscillation circuit using an L T (LiTaO3) piezoelectric vibrator. This is a common emitter type Colpitts oscillation circuit, and a piezoelectric vibrator 2 connected between the base and collector of a transistor 1 gives an oscillation output of a constant frequency to a capacitor 3.4 selected between the piezoelectric element 2 and the ground. A circuit diagram of this oscillation circuit constructed using a digital circuit is shown in FIG.
4 is an integrated NC circuit as shown by a dotted line 5, and is connected in parallel to a parallel circuit of an inverter 6 and a resistor 7, so that the oscillation output of the piezoelectric vibrator 2 is outputted from the inverter circuit 7.

However, since the temperature characteristics of the LT piezoelectric vibrator used in future oscillators will change depending on the area of the drive electrodes 20a and 20b provided on the front and back sides of the LT vibrator 16, slight differences in the configuration of the electrodes will cause the LT piezoelectric The oscillation frequency of the vibrator 16 changes, making it difficult to stabilize the output frequency of the oscillation circuit.

(4) Purpose of the Invention In view of the two conventional drawbacks, the present invention provides an oscillation circuit using a resonator by offsetting the temperature characteristics of the resonator and the temperature characteristics used for the load capacity of the resonator. The object of the present invention is to provide a piezoelectric vibrator that makes it possible to improve the temperature characteristics of a piezoelectric vibrator.

(5) Structure of the Invention According to the present invention, the above object is to provide an oscillation circuit using a high-engagement piezoelectric vibrator. This is achieved by providing a piezoelectric vibrator oscillation circuit characterized in that the blackness characteristic and the confinement amount of the piezoelectric vibrator match the temperature characteristic.

(6) Embodiments of the invention Hereinafter, embodiments of the invention will be described in detail with reference to the accompanying drawings.

FIG. 3 is a diagram showing the structure of the +-T piezoelectric vibrator of the present invention.

In the figure, a lower electrode 13 is provided on the base substrate 12'2, upper electrodes 158, 15b are provided on the lower electrode 13 with a dielectric 14 in between, and the upper electrode 15a, the lower electrode 13, and the dielectric 14 are provided. A capacitor 17a is formed, and the upper electrode 15b, the lower electrode 13, and the dielectric 14 are similarly formed.
A capacitor 17b is formed by the capacitor 17b.

The L T piezoelectric vibrator 16 is connected to the negative electrodes 15a and 15b by soldering or the like, and the T piezoelectric vibrator 16 vibrates at a specific frequency within the drive electrodes 20a and 2Ob.

Further, conductors 182 to 18c are provided on the lower surface of the base substrate 12, and the vibrator 16. ζ capacitors +7a, 17b etc. are enclosed.

When the confinement amount η of the IT piezoelectric vibrator 16 used in the above configuration is changed, the oscillation frequency of the oscillation circuit has the characteristics shown in FIG. 4 due to temperature changes.

Curve A shows the characteristics when η is 0.8, curve B shows the characteristics when η is 1.06, and the following curves C1D,
E shows the characteristics when η is 1.59, 2, 12, 2.65.

Further, the I, T piezoelectric vibrator 16 has a characteristic that its oscillation frequency changes when the thick film capacitors 17a and 17b used as load capacitors change, and FIG. 5 shows the characteristic curve.

In the same figure, the horizontal axis is the capacitance CL of the load capacitances 17a and 17b.
and the capacitance Cd of the equivalent circuit of the L T piezoelectric vibrator shown in Fig. 6.
The vertical axis shows the frequency change ratio. Here CL
The characteristic curve F is obtained by calculating the frequency change ratio d C+) with respect to /Cd.

Here, using the curve shown in FIG. 4 as the confinement amount of the piezoelectric vibrator 16, and calculating the capacitance change with respect to temperature change from the equivalent circuit of the LT piezoelectric vibrator shown in FIG. 6, the curve G shown in FIG. Becomes a characteristic.

This curve G has almost the same characteristics as the characteristics of the thick film capacitor used as the load capacitance shown in FIG. 8 from -25°C to 90°C. That is, by using the LT piezoelectric vibrator 16 with the same characteristics as the capacitance change with respect to temperature of the capacitor 178. % can approach 10''pplYl).

For example, if a thick film capacitor having the temperature characteristics shown in FIG. 8 is used and integrated with the present LT piezoelectric vibrator,
The capacitance of a thick film capacitor changes due to changes in ambient temperature, and as a result, the LT, which changes depending on the capacitor capacitance,
Since the oscillation frequency of the piezoelectric vibrator also changes in the same way, it is possible to always obtain an output of a constant frequency from the oscillation circuit. Therefore, with the structure shown in FIG. 3 of this embodiment, the oscillation circuit always outputs a stable oscillation frequency, and subsequent digital circuits can use this oscillation output as an accurate lock signal.

6-(7) Effect of the invention Iu J = As explained in detail, according to the present invention, 1-
By utilizing the characteristics of both the temperature characteristics of the oscillation frequency changing depending on the amount of confinement of the T piezoelectric vibrator and the fact that the oscillation frequency also changes depending on the load capacity of the LT piezoelectric vibrator, the LT piezoelectric vibration It is possible to prevent the oscillation frequency of the child from changing due to temperature, and to stably maintain the oscillation frequency of the oscillation circuit using the LT piezoelectric vibrator.

[Brief explanation of the drawing]

Fig. 1 is a conventional oscillation circuit diagram, Fig. 2 is a conventional digital oscillation circuit diagram, Fig. 3 is a configuration diagram showing the piezoelectric vibrator and capacitor of the present invention, Fig. 4 is a frequency change ratio characteristic diagram with respect to temperature, FIG. 5 is a frequency change ratio characteristic diagram with respect to capacitance, FIG. 6 is an equivalent circuit diagram of a piezoelectric vibrator, FIG. 7 is a frequency change ratio characteristic diagram with respect to temperature, and FIG. 8 is a capacitance change characteristic diagram with respect to temperature. 12... Heath substrate, 13... Lower electrode,
14...Dielectric, 1.5 a. 15b...'' two-part electrode, 16...LT piezoelectric vibrator, 17a, 17b... capacitor, 18a, 18b, 18c...-conductor electrode,
19...Ceramic cap. 2Qa, 20b'' ・Drive electrode.

Claims (1)

[Claims] An oscillation circuit using a high engagement piezoelectric vibrator, characterized in that the temperature characteristics of a load capacitor used in the oscillation circuit and the temperature characteristics of the vibrator due to the confinement amount of the piezoelectric vibrator match the temperature characteristics of the load capacitor. Piezoelectric vibrator oscillation circuit.