JP2003008353A - Piezoelectric oscillator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small-sized piezoelectric oscillator in which suitable circuit setting is applied. SOLUTION: An oscillation circuit is equipped with a Colpitts type oscillation circuit provided with a transistor for oscillation, a buffering transistor cascode- connected with the transistor for oscillation, a base bias circuit of the buffering transistor, and a bypass capacitor between a power source voltage Vcc and ground. In the base bias circuit, a collector and an emitter of a first transistor are connected in a forward direction with a part between a base of buffering transistor and a power source voltage Vcc line. The base bias circuit constituted of a resistance circuit or a resistance circuit including transistors is connected with a base of the first transistor. As a result, a selection range of base bias setting condition of the buffering transistor is enlarged, and a small-sized crystal oscillator can be provided in which suitable circuit setting is applied, especially, even in the case of a low voltage power source.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oscillator, and more particularly to a small piezoelectric oscillator.

[0002]

2. Description of the Related Art A crystal oscillator is used as a reference signal source for various devices and is available in various sizes depending on the application. A small crystal oscillator is used especially in mobile phones which are becoming smaller. FIG. 4 is a circuit diagram of a conventional small crystal oscillator. The crystal oscillator 100 shown in the figure is a Colpitts-type crystal oscillation circuit 101 in which a buffer circuit 102 is cascode-connected, and each transistor provided in the crystal oscillation circuit 101 and the buffer circuit 102 has a base bias composed of a resistor circuit network. A base potential is appropriately applied by the circuit. Then, by connecting a large-capacity capacitor Cb between the base of the buffer transistor 111 and the ground, the buffer circuit is made into a grounded base type, whereby the load capacitance of the next-stage circuit connected to the oscillator output terminal OUT changes. Influences the oscillation loop. In order to miniaturize such a crystal oscillator,
It is common to make an electric circuit other than the crystal oscillator into an IC (IC-made crystal oscillator). However, when a large-capacity capacitor Cb is made of a semiconductor, the IC chip becomes large and the crystal oscillator is sufficiently miniaturized. There is a problem that it cannot be achieved.

Therefore, as shown in FIG. 5, a crystal oscillator has been proposed in which the capacitor Cb is removed and the crystal oscillator is configured to be suitable for IC. That is, the crystal oscillator 100 shown in the figure includes a Colpitts-type crystal oscillation circuit 101 and a crystal oscillation circuit 101.
And a cascode-connected buffer circuit 102. The crystal oscillating circuit 101 connects a series circuit composed of a capacitor 104 and a capacitor 105, which is a part of a load capacitor, between the base of the oscillating transistor 103 and the ground, and the connection midpoint of the series circuit is the emitter of the transistor 103. And an emitter resistor 106 is connected between this emitter and ground. Further, a base bias circuit including a resistor 107 and a resistor 108 is connected to the base of the transistor 103 so that one end of the resistor 108 is grounded, and a crystal oscillator 109 and a capacitor 110 are provided between the base of the transistor 103 and the ground. Connect a series circuit.

The buffer circuit 102 includes a transistor 11
A resistor 112 is connected between the collector of 1 and the power supply voltage Vcc line.
Connected to the base of transistor 111 and power supply voltage Vcc
The transistor 113 is forward-connected to the line, and the base and collector of the transistor 113 are connected to form a diode configuration. Furthermore, a capacitor 114 is connected as a bypass capacitor between the power supply voltage Vcc line and the ground, the collector of the transistor 111 and the output terminal OUT are connected via a DC cut capacitor 115, and the collector of the transistor 103 and the transistor are connected. The emitter of the transistor 111 is cascode-connected, and the one end of the resistor 107 is connected to the base of the transistor 111. In the crystal oscillator 100 configured in this manner, the base of the transistor 111 is grounded via the transistor 113, and therefore the buffer circuit 102 functions as the grounded base without connecting a bypass capacitor between the base of the transistor 111 and the ground. be able to.

[0005]

However, the crystal oscillator 100 having the above-described structure is not compatible with the transistor 11
Since the voltage between the power supply voltage Vcc line of 1 and the base is determined only by the voltage between the base and the emitter of the transistor 113, there is a problem that the setting conditions of the oscillation circuit are limited. In particular, when the power supply voltage Vcc is low, the voltage between the terminals of the resistor 107 and the voltage between the terminals of the resistor 108 are low values, so the required oscillator function may not be obtained due to some deviation of the base bias setting.
Therefore, since it is necessary to more strictly set the base bias of the transistor 111, it is an important subject to provide the base potential setting condition with wide selectivity.

[0006]

In order to solve the above problems, the present invention according to claim 1 relates to a Colpitts type oscillation circuit having an oscillating transistor, and a buffer cascode-connected to the oscillating transistor. In an oscillator circuit including a transistor, a base bias circuit of the buffer transistor, and a bypass capacitor between the power supply voltage Vcc and ground, the base bias circuit is configured such that the base of the buffer transistor and the power supply voltage Vc
The collector and the emitter of the first transistor are forwardly connected to the c line, and the base of the first transistor is connected to a resistor circuit or a base bias circuit including a resistor circuit including the transistor. . According to a second aspect of the present invention, in addition to the first aspect, the first transistor base bias circuit includes a diode-connected second transistor, and the base of the first transistor and the second transistor. And a resistor connected between the collector of the second transistor and the power supply voltage Vcc line, and the emitter of the second transistor is grounded via the resistor. Is characterized in that. According to a third aspect of the present invention, in addition to the first aspect, the first transistor base bias circuit includes a third transistor having a polarity opposite to that of the other transistors, and the base of the first transistor and the first transistor are provided. The emitter of the third transistor is connected, the emitter is connected to the power supply voltage Vcc line via a resistor, and the collector and base of the third transistor are connected via a resistor, The collector of the transistor is grounded, and the base of the third transistor is connected to the power supply voltage Vcc line through a resistor. According to a fourth aspect of the present invention, the first transistor base bias circuit is configured independently of the oscillation transistor base bias circuit.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below based on the illustrated embodiments. 1 is a circuit diagram showing an embodiment of a crystal oscillator according to the present invention. A crystal oscillator 1 shown in the figure includes a Colpitts-type crystal oscillation circuit 2 and a buffer circuit 3. The crystal oscillating circuit 2 is configured such that a series circuit composed of a capacitor 5 and a capacitor 6, which is a part of a load capacitor, is inserted and connected between the base of the oscillating transistor 4 and the ground. In addition to being connected to the emitter, the emitter is grounded via the emitter resistor 7. Further, a base bias circuit composed of resistors 8 and 9 is connected to the base of the transistor 4, and a series circuit composed of a crystal oscillator 10 and a capacitor 11 is inserted and connected between the base of the transistor 4 and ground. The buffer circuit 3 connects the collector of the transistor 12 to the resistor 1
Connected to the power supply voltage Vcc line through 3, and transistor 1
The collector / emitter of the transistor 14 is inserted in the forward direction between the base of 2 and the power supply voltage Vcc line, and the base of the transistor 12 and the base of the transistor 4 are connected via the resistor 8. Further, the collector of the transistor 15 which connects the base and the collector and functions as a diode is connected to the power supply voltage Vcc line through the resistor 16 and the transistor 1
The emitter of 5 is grounded through a resistor 17, and the collector of the transistor 15 is connected to the base of the transistor 14. That is, the portion 18 surrounded by the broken line is the transistor 1
5, a base bias circuit for the transistor 14, which is composed of resistors 16 and 17.

By connecting a bypass capacitor 19 between the power supply voltage Vcc line and the ground, AC is grounded and the oscillation output is derived from the collector of the transistor 12 through the DC-cutting capacitor 20. . In the crystal oscillator 1 configured in this way, the transistor 12
The base potential Vb12 of is the base potential Vb of the transistor 14.
Vb12 = Vb14-Vbe, which is determined by the potential Vbe between the base and emitter of the transistor 14 and the transistor 14, but the base potential Vb
14 is Vb14 = ((Vcc-Vbe) × R17) / (R16 + R17) + Vbe using the resistance value R16 of the resistor 16, the resistance value R17 of the resistor 17, and the base-emitter potential Vbe of the transistor 15. Can be represented. Therefore, the base potential Vb12 is Vb12 =
Since ((Vcc-Vbe) × R17) / (R16 + R17), the value of the resistors 16 and 17 can be compared with the conventional one in which the base potential of the buffer transistor is fixed to Vcc-Vbe. Can be set as desired, greatly increasing the degree of freedom in design.

FIG. 2 is a circuit diagram showing another embodiment of the crystal oscillator according to the present invention. Crystal oscillator 1-2 shown in the figure
Is characterized in that the degree of freedom in designing the base bias circuit 18 for the transistor 14 is further expanded. That is, the base bias circuit 1 in the crystal oscillator 1-2
Numeral 8 uses a pnp transistor 21 having a polarity opposite to that of the other transistors.
3 and the resistor 24 can be arbitrarily set. In the crystal oscillator 1-2 having this configuration, the base potential Vb12 of the transistor 12 is V12 = V14-Vb
e, the resistance value R23 of the resistor 23, the resistance value R24 of the resistor 24
Since V14 = ((R23 + R24) × R24) / Vcc + Vbe using, it can be expressed as Vb12 = ((R23 + R24) × R24) / Vcc. The degree of freedom of is improved. Furthermore, since the crystal oscillator 1-2 is a combination of a pnp transistor and an npn transistor, the above Vb12 = ((R23 + R24)
× R24) / Vcc, as is clear from transistors 14 and 2
The fluctuations of the base potential of 1 with respect to the temperature change are canceled by each other, and the stable oscillation operation can be maintained even at the ambient temperature.

FIG. 3 is a circuit diagram showing still another embodiment of the crystal oscillator according to the present invention. The crystal oscillator 1-3 shown in the figure is characterized in that the base bias circuit of the oscillating transistor 4 and the base bias circuit of the buffer transistor 12 are independently configured.
That is, in the crystal oscillator 1-3, the base bias of the buffer transistor 14 is derived from the resistor 25 inserted between the emitter of the transistor 14 and the ground, and the base bias transistor 2 of the transistor 14 is further derived.
The base bias of 6 is directly controlled by the voltage between the power supply voltage Vcc line and the ground. At the same time, the base bias for the oscillating transistor 4 is also directly supplied by the voltage between Vcc and the ground. According to the crystal oscillator 1-3 of this configuration, in addition to the function of the crystal oscillator described above, the base biases of the transistor 4 and the transistor 12 are set independently, so that the power supply voltage Vcc is particularly high.
Even when is low, the base bias can be set to an appropriate value. Although the present invention has been described using the crystal oscillator, the present invention is not limited to this.
The present invention can be applied to a piezoelectric oscillator using a W resonator and a vibrator made of a piezoelectric material other than quartz, and any oscillator having a cascode amplifier circuit such as an LC oscillator and a ceramic oscillator.

[0011]

As described above, the piezoelectric oscillator according to the present invention includes a Colpitts type oscillation circuit having an oscillating transistor, a buffer transistor cascode-connected to the oscillating transistor, and a base bias circuit of the buffer transistor. In the oscillation circuit having a bypass capacitor between the power supply voltage Vcc and the ground, the base bias circuit includes a collector and an emitter of the first transistor between the base of the buffer transistor and the power supply voltage Vcc line. Are connected in the forward direction, and a base bias circuit composed of a resistance circuit or a resistance circuit including a transistor is connected to the base of the first transistor. A small crystal whose circuit is properly set even in a voltage power supply. It is possible to provide a vibrator.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a crystal oscillator according to the present invention.

FIG. 2 is a circuit diagram showing another embodiment of the crystal oscillator according to the present invention.

FIG. 3 is a circuit diagram showing another embodiment of the crystal oscillator according to the present invention.

FIG. 4 is a circuit diagram of a conventional crystal oscillator.

FIG. 5 is a circuit diagram of a conventional crystal oscillator.

[Explanation of symbols]

1 crystal oscillator, 2 crystal oscillator circuit, 3 buffer circuit, 4, 12, 14, 15, 21, 26 transistor, 5, 6, 11, 20 capacitance, 7, 8, 9, 13, 1
6, 17, 22, 23, 24, 25, 27, 28, 2
9, 30 resistance, 10 crystal oscillator, 18 base bias circuit, 19 bypass capacitor, 100 crystal oscillator, 101 crystal oscillation circuit, 102 buffer circuit, 1
03 transistors, 104, 105, 110, 11
4,115 Capacity, 106, 107, 108, 112
Resistor, 109 crystal unit, 111, 113 transistor

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Shoji Izumiya             91-5-A, Higashi Kibogaoka, Asahi Ward, Yokohama City, Kanagawa Prefecture             -1 (72) Inventor Toshikazu Uchiyama             2-1-1 Kotani, Samukawa-cho, Takaza-gun, Kanagawa Prefecture               Toyo Communication Equipment Co., Ltd. (72) Inventor Hosaka             2-1-1 Kotani, Samukawa-cho, Takaza-gun, Kanagawa Prefecture               Toyo Communication Equipment Co., Ltd. F term (reference) 5J079 AA04 BA44 FA02 FA21 FB47                       GA14 KA05

Claims (4)

[Claims] 1. A Colpitts oscillator circuit including an oscillating transistor, a buffer transistor cascode-connected to the oscillating transistor, a base bias circuit of the buffer transistor, and a bypass between a power supply voltage Vcc and ground. In the oscillator circuit including a capacitor, the base bias circuit forward-connects the collector and the emitter of the first transistor between the base of the buffer transistor and the power supply voltage Vcc line, and A piezoelectric oscillator in which a base bias circuit including a resistance circuit or a resistance circuit including a transistor is connected to the base of the transistor. 2. The base bias circuit for the first transistor includes a diode-connected second transistor, the base of the first transistor and the collector of the second transistor are connected, and the second transistor is connected. 2. A circuit configured to connect a resistor between the collector of the transistor and the power supply voltage Vcc line, and to ground the emitter of the second transistor via the resistor. Piezoelectric oscillator. 3. The base bias circuit for the first transistor includes a third transistor having a polarity opposite to that of the other transistors, and connects the base of the first transistor to the emitter of the third transistor. The emitter is connected to the power supply voltage Vcc line via a resistor, the collector and the base of the third transistor are connected via a resistor, and the collector of the third transistor is grounded.
2. The piezoelectric oscillator according to claim 1, wherein the base of the third transistor is connected to the power supply voltage Vcc line via a resistor. 4. The piezoelectric oscillator according to claim 1, wherein the first transistor base bias circuit is configured independently of the oscillation transistor base bias circuit.