JPH10173441A - Oscillating circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an oscillating circuit miniaturized and having fine temperature characteristics concerning an oscillating circuit having fine temperature characteristics used in mobile object communication or the like. SOLUTION: This circuit is provided with a serially-connected body of a capacitor 25 and a capacitor 26 which are connected between the base and the earth of a transistor 21 forming a Colpitts oscillating circuit, a crystal oscillator 27 of which one of terminals is connected to the aforementioned base, and a parallel-connected body of a variable capacitor 28 and a fixed capacitor 29 connected between another terminal of this crystal oscillator 27 and the earth, and the capacitor 25 and the capacitor 26 of the serially-connected body and the crystal oscillator 27 have temperature characteristics for mutually supplementing. Thus, the temperature characteristics are stabilized and miniaturization is realized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oscillation circuit having good temperature characteristics and used for mobile communication.

[0002]

2. Description of the Related Art A conventional oscillation circuit will be described below.

In a conventional oscillation circuit, as shown in FIG. 3, a series connection of a capacitor 2 and a capacitor 3 is connected between the base of a transistor 1 constituting a Colpitts oscillation circuit and ground, and a power supply 4 is connected to the base. It is connected to the base from the side via a resistor 5. The base is connected to the ground via a resistor 6. A variable resistor 8 and a resistor 9 having a temperature characteristic are provided at the base of the transistor 1.
Is connected to one terminal of a first parallel-connected body 10 in which the capacitor 7 is connected in parallel with the series-connected body. A capacitor 11, a resistor 12 having a temperature characteristic, and a variable resistor 13 are connected to the other terminal of the first parallel connection body 10.
Are connected in parallel to one terminal of a second parallel connection body 14, and the other terminal is connected to one terminal of a crystal resonator 15, and the other terminal of the crystal resonator 15 is connected to the other terminal. The terminals are the variable capacitor 16 and the fixed capacitor 1
7 are connected to the ground through the parallel connection body. The collector of the transistor 1 is connected to the output terminal 18, the emitter of the transistor 1 is connected to the ground via a resistor 19, and is connected to the connection point between the emitter and the capacitors 2 and 3.

[0004]

However, in such a conventional structure, the first structure is required to stabilize the temperature characteristics.
Resistor 9 having a temperature characteristic used in parallel connection body 10 of FIG.
And the variable resistor 8, and furthermore, the resistor 12 and the variable resistor 13 having the temperature characteristics used for the second parallel-connected body 14 are required, and the number of components is very large. Therefore, there is a problem that the size of the device is inevitably increased for use in a small device such as a mobile communication device.

An object of the present invention is to solve such a problem, and an object of the present invention is to provide an oscillation circuit which is reduced in size and has good temperature characteristics.

[0006]

In order to achieve this object, an oscillation circuit according to the present invention comprises a first circuit connected between a base of a transistor constituting a Colpitts oscillation circuit and ground.
And a crystal resonator having one terminal connected to the base, and a second capacitor connected between the other terminal of the crystal resonator and ground. The crystal oscillator has a configuration in which temperature characteristics complement each other.

As a result, the temperature characteristics can be stabilized and the size can be reduced.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention is directed to a first capacitor connected between a base of a transistor constituting a Colpitts oscillation circuit and ground, and one terminal connected to the base. A connected crystal oscillator, and a second capacitor connected between the other terminal of the crystal oscillator and the ground, wherein the first capacitor and the crystal oscillator complement each other in temperature characteristics. Since the first capacitor and the crystal unit have temperature characteristics that complement each other, the circuit is stable with respect to temperature, and the circuit for correcting temperature characteristics can be simplified. Therefore, the number of parts is reduced and the size can be reduced. Further, since the number of components is reduced, a low-cost oscillation circuit can be provided.

The invention according to claim 2 is the oscillation circuit according to claim 1, wherein the second capacitor is a variable capacitor. Since the second capacitor is a variable capacitor, the oscillation frequency is varied. be able to.

A first capacitor according to a third aspect of the present invention is the oscillation circuit according to the first aspect, wherein two capacitors having substantially the same capacitance are connected in series, and thus the temperature characteristics of the two capacitors are two. Fine adjustment of the temperature characteristics can be easily performed.

The invention according to claim 4 is the oscillation circuit according to claim 1, wherein a fixed capacitor is connected in parallel with the second capacitor. By connecting the fixed capacitor and the variable capacitor in parallel as described above, , The frequency can be easily adjusted.

According to a fifth aspect of the present invention, there is provided the oscillation circuit according to the fourth aspect, wherein the temperature characteristic of the fixed capacitor is such that the capacitance variation with respect to temperature is minute. By using a fixed capacitor having little variation easily with temperature in parallel, the oscillation frequency becomes stable with temperature.

According to a sixth aspect of the present invention, there is provided the oscillation circuit according to the first aspect, wherein a first capacitor is arranged near the crystal unit, and a pattern leading from the first capacitor to the crystal unit is shortened. As a result, unnecessary pattern inductance components can be removed, and stable oscillation can be obtained. As a result, stability against temperature increases.

According to a seventh aspect of the present invention, there is provided the oscillation circuit according to the first aspect, wherein the crystal resonator and the first capacitor are each divided in temperature characteristics in advance. By dividing in advance, productivity can be improved, and an oscillation circuit having better temperature characteristics can be realized.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a circuit diagram of an oscillation circuit according to the present invention. In FIG. 1, reference numeral 21 denotes an NPN transistor. The emitter of this transistor 21 is a resistor 22
Connected to earth through On the other hand, the base is resistor 2
3 and connected to the power supply 37 side, and to the ground via the resistor 24. The base of the transistor 21 is connected to the ground by connecting a capacitor 25 and a capacitor 26 in series. The connection point between the capacitors 25 and 26 and the emitter of the transistor 21 are connected. The base of the transistor 21 is connected to one terminal of a crystal oscillator 27, and the other terminal of the crystal oscillator 27 is connected to ground via a parallel connection of a variable capacitor 28 and a fixed capacitor 29. . The transistor 21
Is connected to the power supply 37 side through a resistor 30, and is connected to the base of the second transistor 32 by a capacitor 31. The emitter of the transistor 32 is connected to the ground, and the collector is connected to the output terminal 34 via the capacitor 33. A resistor 35 is connected between the base and the collector of the transistor 32, and the collector is connected to the power supply 37 via the resistor 36.

As described above, a Colpitts type oscillation circuit is configured. Here, the capacitor 25 and the capacitor 2
6 has the same capacity and has temperature characteristics.
This uses the one that corrects the temperature characteristics of the crystal unit 27. Further, the variable capacitor 28 is a trimmer capacitor having a very small capacity, and its capacity is at most half that of the fixed capacitor 29. Therefore, fine adjustment of the frequency can be easily performed. Further, since the capacitor 25, the capacitor 26, and the crystal unit 27 have a relationship that complements the temperature characteristics, the stability with respect to the temperature condition is good.

FIG. 2 is a plan view of a main part of the oscillation circuit. FIG.
As shown in FIG.
Is provided in parallel with the end face of the crystal unit 27, and the other end of the capacitor 25 is bent at a right angle to form the capacitor 2.
6 are arranged. By providing the capacitors 25 and 26 in the vicinity of the crystal unit 27 in this manner, the pattern 3 between the crystal unit 27 and the capacitor 25
8 becomes shorter, and unstable elements for oscillation can be removed. Therefore, the stability with respect to temperature increases. It is important that the fixed capacitor 29 has a small capacity variation with temperature. This can prevent the oscillation frequency from changing with temperature.

[0018]

As described above, according to the present invention, the first capacitor connected between the base of the transistor constituting the Colpitts oscillation circuit and the ground, and the crystal having one terminal connected to the base. A structure including a resonator and a second capacitor connected between the other terminal of the crystal resonator and the ground, wherein the first capacitor and the crystal resonator have temperature characteristics that complement each other. It was done. Accordingly, the first capacitor and the crystal unit have temperature characteristics that complement each other, so that the first capacitor and the crystal unit are stable with respect to temperature, and a circuit for correcting temperature characteristics can be simplified. Therefore, the number of parts is reduced and the size can be reduced. Further, since the number of components is reduced, a low-cost oscillation circuit can be provided. In addition, by using the first capacitor that complements the temperature characteristics of the crystal unit, the number of components can be reduced, and as a result, the cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of an oscillation circuit according to an embodiment of the present invention.

FIG. 2 is a plan view of a main part of the oscillation circuit.

FIG. 3 is a circuit diagram of a conventional oscillation circuit.

[Explanation of symbols]

 21 Transistor 25 Capacitor 26 Capacitor 27 Crystal Resonator 28 Variable Capacitor 29 Fixed Capacitor

Claims (7)

[Claims] 1. A first capacitor connected between a base of a transistor constituting a Colpitts oscillation circuit and ground, a crystal oscillator having one terminal connected to the base, and the other of the crystal oscillator An oscillation circuit comprising: a second capacitor connected between the first terminal and the ground; and wherein the first capacitor and the crystal unit have temperature characteristics that complement each other. 2. The oscillation circuit according to claim 1, wherein the second capacitor is a variable capacitor. 3. The oscillation circuit according to claim 1, wherein the first capacitor comprises two capacitors having substantially the same capacitance connected in series. 4. The oscillation circuit according to claim 1, wherein a fixed capacitor is connected in parallel with the second capacitor. 5. The oscillation circuit according to claim 4, wherein the temperature characteristic of the fixed capacitor is such that a capacitance fluctuation with respect to temperature is small. 6. The oscillation circuit according to claim 1, wherein a first capacitor is provided near the crystal unit. 7. The oscillation circuit according to claim 1, wherein each of the crystal unit and the first capacitor has a temperature characteristic previously classified.