JP2003060434A - Oscillator and electronic apparatus using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an oscillator capable of supplying a necessary base current, by suppressing a power consumption as much as possible by a resistor for supplying a base current, and to provide an electronic device using the same. SOLUTION: The oscillator comprises a resonance circuit 2, a transistor Q1 for an oscillation having a collector connected to a power source terminal Vb and grounded in a high-frequency manner, a base connected to the circuit 2 and connected to a base current supply circuit (R1, R2), a feedback capacitor C1 connected between the base and an emitter connected to a base of a transistor Q2 for a buffer, in such a manner that the transistor Q1 and the transistor Q2 are formed into a Darlington connection configuration. Accordingly, a base current supply circuit to the transistor for the buffer is not necessary, the power consumption can be reduced, and the number of components can be decreased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oscillator such as a voltage controlled oscillator and an electronic device using the oscillator.

[0002]

2. Description of the Related Art In oscillators used in mobile phones and the like, low power consumption is strongly demanded. As an oscillator for realizing such low power consumption, for example, there is an oscillator disclosed in Japanese Patent Laid-Open No. 10-150321. In the oscillator disclosed in Japanese Patent Laid-Open No. 10-150321, a buffer transistor and an oscillating transistor are connected in a cascade, and a current flowing between the collector and the emitter of the buffer transistor is applied between the collector and the emitter of the oscillating transistor. The current is also effectively used by flowing the current. Further, three resistors connected in series are connected between the power supply terminal and the ground, and the connection point of each resistor is connected to the bases of the buffer transistor and the oscillation transistor to supply the base current.

[0003]

By the way, in such an oscillator, the current flowing through the resistor for supplying the base current is also an obstacle to reducing the current consumption. However, if an attempt is made to suppress the power consumption by increasing the resistance value of the resistance for supplying the base current, the supply of the base current to the buffer transistor and the oscillation transistor becomes insufficient, and the oscillation output level decreases, There is a problem that the base bias becomes unstable and the C / N characteristic of the oscillator deteriorates.

An object of the present invention is to solve the above problems and to provide an oscillator capable of supplying a necessary base current while suppressing power consumption by a resistor for supplying a base current as much as possible. An electronic device using is provided.

[0005]

To achieve the above object, an oscillator of the present invention is an oscillator circuit having a resonance circuit, an oscillation transistor, and a buffer transistor, wherein the oscillation transistor has a collector. The buffer transistor is connected to a power supply terminal, the base is connected to the resonance circuit and the base current supply circuit, and a feedback capacitor is connected between the base and the emitter. The connection is made and the base is connected to the emitter of the oscillation transistor to form a Darlington connection structure together with the oscillation transistor.

In the oscillator of the present invention, the buffer transistor has a collector connected to the power supply terminal through a load impedance and an output terminal, and an emitter grounded through a ground resistance. It is characterized by

Further, in the oscillator of the present invention, in the base current supply circuit, one end of a series circuit composed of two resistors is connected to the power supply terminal, the other end is grounded, and the connection point of the two resistors is the above. It is characterized in that it is connected to the base of the oscillation transistor.

An electronic device of the present invention is characterized by using the above oscillator.

With this configuration, the oscillator of the present invention can reduce power consumption and the number of parts.

In the electronic device of the present invention, the power consumption can be reduced by using the oscillator of the present invention.

[0011]

1 is a circuit diagram of an embodiment of the oscillator of the present invention. In FIG. 1, the oscillator 1 includes an oscillation transistor Q1, a buffer transistor Q2, a feedback capacitor C1, capacitors C2 to C5, a resistor R1,
R2, ground resistance R3, inductance element L1, resonance circuit 2, power supply terminal Vb, and output terminal Po.

Of these, the power supply terminal Vb is the capacitor C5.
Is grounded through and is connected to the collector of the oscillation transistor Q1. The power supply terminal Vb is grounded via the resistors R1 and R2 in series. The base of the oscillating transistor Q1 is connected to the connection point between the resistors R1 and R2, and further connected to the resonance circuit 2. A feedback capacitor C1 is connected between the base and emitter of the oscillation transistor Q1.

Further, the power supply terminal Vb is connected to the collector of the buffer transistor Q2 via the inductance element L1. The emitter of the buffer transistor Q2 is grounded through the grounding resistor R3 and also through the capacitor C2. The base of the buffer transistor Q2 is connected to the emitter of the oscillation transistor Q1, and as a result, the oscillation transistor Q1 and the buffer transistor Q2 have a Darlington connection structure. The collector of the buffer transistor Q2 is grounded via the capacitor C3 and is connected to the output terminal Po via the capacitor C4.

Here, the collector of the oscillating transistor Q1 is grounded at a high frequency by a capacitor C5. In this case, being grounded at a high frequency means that the impedance of the capacitor C5 approaches zero at frequencies around the oscillation frequency or higher.
This means that in such a high-frequency signal, the state is substantially the same as that of being grounded. The base current is supplied to the base of the oscillation transistor by the resistors R1 and R2 that form the base current supply circuit. Therefore, the collector transistor grounded Colpitts oscillator circuit is constituted by the oscillation transistor Q1, the resonance circuit 2, the feedback capacitor C1, and the circuit after the buffer transistor Q2 which functions as a capacitive element.

The output signal of this Colpitts oscillator circuit is input from the emitter to the base of the buffer transistor Q2. At this time, since the oscillation transistor Q1 and the buffer transistor Q2 have a Darlington connection structure, the current supplied to the base of the buffer transistor Q2 is higher than the current supplied to the base of the oscillation transistor Q1. , The current amplification factor of the oscillation transistor Q1 increases. Therefore, a necessary and sufficient current is supplied to the base of the buffer transistor Q2. The signal amplified by the buffer transistor Q2 is output from the output terminal Po from the collector through the capacitor C4.

In the oscillator 1 thus configured, the base current can be sufficiently supplied by the Darlington-connected oscillation transistor Q1 although the base current supply circuit for the buffer transistor is not provided. Therefore, the oscillation transistor Q1
The base current supply circuits (R1, R2) for the above can be made to flow only a minimum current, and the current consumption can be reduced, that is, the power consumption can be reduced. Further, since the base current supply circuit for the buffer transistor Q2 is unnecessary, the number of parts can be reduced. Further, since the buffer transistor Q2 exists between the oscillating transistor Q1 and the output terminal Po, the stability with respect to the load fluctuation is enhanced as in the conventional oscillator in which the oscillating transistor and the buffer transistor are cascade-connected. be able to.

FIG. 2 shows another embodiment of the oscillator of the present invention. 2, parts that are the same as or equivalent to those in FIG. 1 are given the same symbols, and descriptions thereof will be omitted.

The oscillator 10 shown in FIG. 2 is different from the oscillator 1 shown in FIG. 1 only in that an inductance element L2 is provided between the power supply terminal Vb and the collector of the oscillation transistor Q1. . In this case, in order to ground the collector of the oscillating transistor Q1 at a high frequency, the value may be set such that the inductance element L2 and the capacitor C5 resonate in series at the oscillation frequency.

Also in the oscillator 10 configured as described above, the power consumption can be reduced as in the case of the oscillator 1, and the stability with respect to the load fluctuation can be enhanced. Further, since the inductance element L2 can be realized by wiring on the printed circuit board, this does not cause an adverse effect of increasing the number of parts. Further, the inductance element L2 is used to connect the oscillation transistor Q1 to the power supply terminal V
It is also possible to obtain the effect of preventing the oscillation signal from leaking to b.

FIG. 3 shows still another embodiment of the oscillator of the present invention. 3, parts that are the same as or equivalent to those in FIG. 2 are given the same symbols, and descriptions thereof are omitted.

The oscillator 20 shown in FIG. 3 is different from the oscillator 10 shown in FIG. 2 only in that a resistor R4 is provided in place of the inductance element L2.

Also in the oscillator 20 configured as described above, the power consumption can be reduced as in the case of the oscillator 10, and the stability against the load fluctuation can be enhanced. Further, when the resistor R4 is realized by, for example, a printing resistor, this does not cause an adverse effect that the number of parts increases. Furthermore, the resistor R4 can also prevent the oscillation signal from leaking from the collector of the oscillation transistor Q1 to the power supply terminal Vb.

Although only one buffer transistor Q2 is used in each of the above embodiments, another buffer transistor is connected to the collector which is the output of the buffer transistor Q2 to make the buffer a plurality of stages. However, the stability against load fluctuation can be further increased. However, the other buffer transistor in this case does not have the Darlington connection structure.

Further, in each of the above-described embodiments, an example in which the structure in which the oscillation transistor and the buffer transistor are connected in Darlington connection is applied to the oscillator which oscillates at a single frequency is shown. In addition, the present invention may be applied to a voltage-controlled oscillator in which the resonance frequency, and thus the oscillation frequency, can be changed by the voltage applied to the varactor diode.

Further, in each of the above-described embodiments, the method for realizing the circuit is not particularly limited, and it is described as if it is an oscillator using discrete transistors, resistors and capacitors. An oscillator using an integrated IC may be used, and it is possible to obtain the same operational effect as in the case of using discrete parts, and further reduce the number of parts.

FIG. 4 is a perspective view of an embodiment of the electronic device of the present invention. In FIG. 4, a mobile phone 30, which is one of the electronic devices, includes a housing 31, a printed circuit board 32 arranged therein, and the oscillator 1 of the present invention mounted on the printed circuit board 32.

In the mobile phone 30 having such a structure, since the oscillator 1 of the present invention is used, the power consumption can be reduced. Moreover, since the oscillator having high stability against load fluctuation is used, the stability of performance can be improved.

Although a mobile phone is shown as the electronic device in FIG. 4, the electronic device is not limited to the mobile phone, and any device using the oscillator of the present invention may be used.

[0029]

According to the oscillator of the present invention, the emitter of the oscillating transistor is connected to the base of the buffer transistor to form a Darlington connection structure, thereby reducing power consumption and the number of parts. it can.

Further, according to the electronic device of the present invention, by using the oscillator of the present invention, it is possible to reduce power consumption and improve performance stability.

[Brief description of drawings]

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

FIG. 2 is a circuit diagram showing another embodiment of the oscillator of the invention.

FIG. 3 is a circuit diagram showing still another embodiment of the oscillator of the present invention.

FIG. 4 is a perspective view showing an embodiment of an electronic device of the present invention.

[Explanation of symbols]

1, 10, 20 ... Oscillator 2 ... Resonance circuit Q1 ... Oscillation transistor Q2 ... Transistor for buffer C1 ... Feedback capacitor C2-C5 ... Capacitor R1 to R4 ... Resistance L1, L2 ... Inductance element Po ... Output terminal Vb ... Power supply terminal 30 ... Mobile phone

Claims (4)

[Claims] 1. An oscillation circuit having a resonance circuit, an oscillation transistor, and a buffer transistor, wherein the oscillation transistor has a collector connected to a power supply terminal, a base connected to the resonance circuit, and a base current. The buffer transistor is connected to a supply circuit and a feedback capacitor is connected between the base and the emitter, and the buffer transistor has a collector connected to the power supply terminal and a base connected to the emitter of the oscillation transistor. According to the above, the oscillator has a Darlington connection structure together with the oscillation transistor. 2. The buffer transistor has a collector connected to the power supply terminal via a load impedance and an output terminal, and an emitter grounded via a ground resistance. The oscillator according to claim 1, wherein 3. The base current supply circuit is configured such that one end of a series circuit including two resistors is connected to the power supply terminal and the other end is grounded, and a connection point of the two resistors is a base of the oscillation transistor. The oscillator according to claim 1, wherein the oscillator is connected. 4. An electronic device using the oscillator according to any one of claims 1 to 3.