JP3136618B2 - Voltage controlled oscillator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voltage controlled oscillator used in a mobile communication device such as a cordless telephone.

[0002]

2. Description of the Related Art In recent years, mobile communication devices such as cordless telephones have been demanded to be smaller, lighter, and have lower current consumption, and these demands have also increased for voltage-controlled oscillators that affect the performance of the devices. ing.

Hereinafter, a conventional voltage controlled oscillator will be described with reference to the drawings. Figure 2 is a circuit diagram showing an example of a specific circuit of a conventional voltage controlled oscillator, in FIG. 2, it is formed by the air-core coil L _1, a capacitor C _5, C _6, C ₇ and variable capacitance diode D ₁ using a resonant circuit is a transistor Q ₁ as Colpitts oscillator to take out the output from the emitter collector grounded type, take out the oscillation output from the Colpitts oscillator through an emitter grounded type buffer amplifier using the transistor Q ₂ Had a configuration.

R _{7 to} R ₁₂ are resistors, C _{1 to} C ₁₀ are capacitors, and L _{1 to} L ₃ are inductances. Reference numeral 6 denotes a voltage control terminal, 7 denotes a power supply terminal, and 8 denotes an oscillation output terminal.

[0005]

However, in the configuration of the above-mentioned conventional example, since current flows through each of the oscillating section and the buffer amplifying section, there is a limit in reducing current consumption. In addition, even if an attempt is made to make the IC smaller and lighter,
There is a problem that it is difficult to make full use of the advantages of the formation.

An object of the present invention is to solve the above-mentioned conventional problems and to provide a voltage-controlled oscillator with low current consumption .

[0007]

In order to achieve this object, a voltage controlled oscillator according to the present invention comprises a resonance circuit connected to a base.
First transistor and the first transistor
Is grounded via the first resistor, and
An emitter signal of the first transistor is supplied to a base
Second transistor, and the second transistor
An output terminal to which the collector signal of
The collector of the transistor and the emitter of the second transistor
Grounding means that is connected to the
The constant voltage circuit connected to the power supply terminal and the constant voltage circuit
A third transistor whose output is connected to the base, and
When the output of the emitter of the third transistor is supplied,
Fourth transistor with base and collector connected together
Between the emitter of the fourth transistor and the ground.
A second resistor connected between the third transistor and the third resistor
Between the emitter of the first transistor and the base of the first transistor
A third resistor connected to the power supply terminal and the second transistor;
A fourth resistor connected between the transistor and the base of the transistor,
Connected between the base of the second transistor and ground.
A fifth resistor, and at least the first to the fifth
4 transistor, the first to fifth resistors and the constant current
The voltage circuit is an integrated circuit .

[0008]

With this configuration, the first transformer constituting the oscillator is formed.
The second part of the transistor collector and buffer amplifier
The emitter of the transistor is cascaded
Therefore, the current can be reduced .

[0009]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing an example of a specific circuit of a voltage controlled oscillator integrated into an IC according to the present invention. In FIG. 1, components having the same functions as those in FIG. 2 will be described by assigning the same reference numerals. Also, the dotted line in the figure indicates IC
It shows the part where the conversion was performed.

[0010] Connect the collector and emitter of the buffer amplifier transistor Q ₂ of the oscillation transistor Q ₁ in FIG. 1, grounding capacitor C _2, C _2a (C _2a is IC
The oscillator becomes a common-collector type, and the buffer amplifier becomes a common-emitter type.

With respect to the oscillating section, a feedback capacitor C ₃ is connected between the collector terminal 3 and the emitter terminal 4 of the transistor Q ₁ , a feedback capacitor C ₄ is connected between the emitter terminal 4 and the base terminal 5, and the feedback terminal is connected to the base terminal 5. , air-cored coils L _1, capacitor C ₅ -C ₇ and the transistor connected to the oscillation output of the resonant circuit formed by a varicap diode D ₁ etc. Q ₁
Taken out from the emitter, it is input to the base of the transistor Q ₂ via the IC of the capacitance C _1.

As for the buffer amplifier, the transistor Q
Output tuning circuit between the _second collector terminal 2 and the power supply terminal 1 is formed by a coil L ₃ and capacitor C ₈ is connected, via a coupling capacitor C _9, is output from the output terminal 8. The bias supply, the reference voltage of an IC constant voltage circuit (bandgap circuit) 9 of the output terminal 9a, via a bias temperature compensation circuit formed by the transistors Q _3, Q ₄ and the resistor R ₄ to R ₆ transistors and supplies the base bias of Q _1. Base bias of the transistor Q ₂ is being supplied with bleeder resistor format.

[0013] In the voltage controlled oscillator constructed in an IC as described above, since the current flowing through the oscillation transistor Q _1, the buffer amplifier transistor Q ₂ are the same path, the current consumption of the half compared with the conventional example Become. Further, by supplying a bias by a bias temperature compensating circuit which is made into an IC, the current flowing through the transistors Q ₁ and Q ₂ can be made constant, and the oscillation output level is stabilized.

[0014] In the configuration cascading oscillator Thus, noise is likely to ride in the collector grounding point of the transistor Q _1, there are cases where C / N deterioration becomes a problem,
Of the noise is amplified by the transistors Q _1, Q _2, etc. In this embodiment, since the noise phase component is prevented from riding the collector of the transistor Q _1, of each of the transistors Q ₁ and Q ₂ based alternative bias Supply has been resolved, and the resistance bleeder format has been eliminated.

In this embodiment, as a 300 MHz band voltage controlled oscillator, 3 V, 4 mA, oscillation output -3 dBm, C / N
75 dB / 8 KHz: Performance such as detuning frequency of 12.5 KHz could be obtained.

[0016]

As described above, in the voltage controlled oscillator according to the present invention , the collector of the first transistor constituting the oscillator is provided.
Of the second transistor constituting the buffer amplifier
Cascade connection with the
Can be Also, the bias of the first transistor
The circuit and the bias circuit of the second transistor are independent of each other.
Using a bias circuit
C / N performance is improved without any influence. Furthermore,
Transistors, resistors and constant voltage circuits are integrated
Thus, downsizing can be achieved. Furthermore, constant voltage circuit
Stable voltage control against power supply fluctuations
An oscillator can be realized.

[Brief description of the drawings]

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

FIG. 2 is a circuit diagram showing a configuration of a conventional voltage controlled oscillator.

[Explanation of symbols]

Q ₁ Transistor for oscillation Q ₂ Transistor for buffer amplifier Q ₃ , Q ₄ Transistor for temperature compensation circuit D ₁ Varicap diode R _{1 to} R ₁₂ Resistance C _{1 to} C ₁₀ Capacitor L _{1 to} L ₃ Inductance 1 Power supply terminal 2, 3 Collector terminal 4 Emitter terminal 5 Base terminal 6 Voltage control terminal 7 Power supply terminal 8 Oscillation output terminal 9 Constant voltage circuit 10 IC part

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H03B 5/00-5/42

Claims (1)

(57) [Claims] 1. A first transistor having a resonance circuit connected to a base.
The transistor and the emitter of this first transistor are
1 and grounded through the first resistor.
A second transistor in which the emitter signal of the transistor is supplied to the base
A transistor and a collector signal of the second transistor
And an output terminal to which the first transistor is connected.
Is connected to the emitter of the second transistor.
Connected to the power supply terminal
Constant voltage circuit and the output of this constant voltage circuit
A third transistor connected to the third transistor;
The output of the emitter of the
And a fourth transistor having the collector connected together.
4 connected between the emitter of the transistor and ground.
A second resistor, an emitter of the third transistor and a
A third transistor connected to the base of the first transistor;
Resistance of the power supply terminal and the second transistor.
A fourth resistor connected between the second resistor and the second transistor.
Fifth resistor connected between transistor base and ground
And at least the first to fourth transistors
And the first to fifth resistors and the constant voltage circuit are integrated.
Of voltage controlled oscillator.