JP2003218634A - Oscillation circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an oscillation circuit that solves a problem of variations in the oscillation frequency due to fluctuations in a power supply voltage because no sufficient voltage is applied to transistors being components of a current source caused by fluctuations in the resistance and β or the like of the transistors. <P>SOLUTION: This invention is attained by a circuit configuration where bases and collectors of the transistors are connected to a power supply and voltages of emitters are fed to a negative resistance circuit as vias voltages. Since a base voltage Vb is set to a voltage dropped from the power supply VCC by a prescribed voltage and the circuit elements for deciding the frequency of a voltage controlled oscillation circuit is not fluctuated against the power supply voltage, fluctuations in the oscillated frequency can be reduced. <P>COPYRIGHT: (C)2003,JPO

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 circuit, and more particularly, it is suitable for an integrated circuit for wireless communication.

[0002]

2. Description of the Related Art An example of a conventional voltage controlled oscillator circuit is IEEE C
ommunication Magazine January 2000 issue 142
Pages 147 to 147. FIG. 2 shows the configuration of the voltage oscillating circuit described in the above magazine.

A conventional voltage controlled oscillator circuit is a current source (1 to 1
3), resistors (4-8), inductors (9, 10), capacitors (11-15), variable capacitors (16, 17), and transistors (18, 19).

One terminal of each of the two inductors 9 and 10 is connected to the power supply (Vcc), and the other terminal is connected to the collector terminal of the transistor 18 and the collector terminal of the transistor 19. In addition, transistor 1
The emitter terminals of 8 and 19 are connected to the current source 2 and the current source 3 which are independent of each other.

A frequency control signal (VC
TRL) is input from the outside and is connected to two resistors 5 and 6. The other terminal of the resistor 5 is grounded via the variable capacitor 16, and the other terminal of the resistor 6 is grounded via the variable resistor 17. The connection point between the resistor 5 and the variable resistor 16 is connected to the connection point between the inductor 9 and the collector terminal of the transistor 18 via the capacitor 11, and the connection point between the resistor 6 and the variable resistor 17 is connected via the capacitor 12. It is connected to the connection point between the inductor 10 and the collector terminal of the transistor 19.

Next, the base electrode of the transistor 18 is supplied with a bias voltage through the resistor 7 and the transistor 1
A bias voltage is applied to the base electrode 9 through the resistor 8. The two bias voltages (Vb) are common, the other terminals of the resistors 7 and 8 are connected to each other, and are generated by the resistor 4 connected to the power source and the current source 1 connected to the other terminal of the resistor 4. R.

[0007]

The voltage controlled oscillator circuit having such a circuit configuration has a capacitor 11 and a variable capacitor 16.
An oscillating operation is performed at the resonance frequency of the resonance circuit of the parallel capacitance component of and the inductor 9. Therefore, the VCR
The oscillation frequency is controllable by TL. Two transistors 18 and 19 and a positive feedback capacitor 13,
By 14, a negative resistance circuit can be realized and the oscillation generated in the resonance circuit can be continued.

However, in the circuit configuration shown in FIG. 2, the bias voltage (Vb) changes depending on the resistance value and the current multiplication factor β which is a parameter of the transistor.
The impedance of the negative resistance circuit composed of the transistors 18 and 19 and the capacitors 13 and 14 changes, and not only the oscillation frequency fluctuates but also the resistance value deviates to the larger side, and β of the transistor decreases When there is a deviation, Vb shifts to a lower voltage, so current sources 2, 3
There is a possibility that a sufficient voltage will not be applied to the transistor that constitutes the transistor and oscillation failure may occur.

[0009]

The conventional circuit system is a system in which a resistor is used to cause a constant voltage drop from a power source and the voltage is supplied as a bias voltage. In this case, even if the constant current characteristic of the current source 1 is improved, it is difficult to stabilize the bias voltage. Therefore, it is possible to stabilize the bias voltage by using the base-emitter voltage of the transistor in the bias voltage generation unit. Becomes The base-emitter voltage of a transistor is described on page 282 of "Analog Integrated Circuit Design Techniques (above)" by Gray Meyer and co-driver, and a nearly constant voltage drop can be obtained under the condition that the transistor is biased in the active region. It is known.
Therefore, stabilization of the bias voltage can be achieved by a circuit configuration in which the base and collector of the transistor are connected to the power supply and the emitter is supplied as a bias voltage to the negative resistance circuit, as compared with the conventional circuit configuration.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described with reference to FIG.

The voltage controlled oscillator circuit according to the present invention comprises a current source (1
.About.3), resistors (5 to 8), inductors (9, 10), capacitors (11 to 15), variable capacitors (16, 17), and transistors (18 to 20).

An external power supply (VCC) is supplied to the voltage control circuit.
The frequency control signal (VCTRL) and GND are supplied. First, one terminal of the two inductors 9 and 10 is
Each is connected to VCC, and the other terminal is connected to the collector terminal of the transistor 18 and the collector terminal of the transistor 19. Further, the emitter terminals of the transistors 18 and 19 are connected to the independent current sources 2 and 3, respectively. These current sources 2 and 3 are connected to GND.

VCTRL is connected to the two resistors 5 and 6. The other terminal of the resistor 5 is grounded via the variable capacitor 16, and the other terminal of the resistor 6 is grounded via the variable resistor 17. The connection point between the resistor 5 and the variable resistor 16 is connected to the inductor 9 and the transistor 18 via the capacitor 11.
Connected to the collector terminal of the
The connection point between the variable resistor 17 and the variable resistor 17 is connected to the connection point between the inductor 10 and the collector terminal of the transistor 19 via the capacitor 12.

Next, the base electrode of the transistor 18 is supplied with a bias voltage through the resistor 7 and the transistor 1
A bias voltage is applied to the base electrode 9 through the resistor 8. The two bias voltages (Vb) are common, and the other terminals of the resistors 7 and 8 are connected to each other.

Vb is connected to the current source 1 grounded to GND, the collector terminal and the base terminal are connected to the emitter terminal of the transistor 20 connected to VCC, and a bias voltage is supplied.

Here, when the current value of the current source 1 is Ic, the base-emitter voltage of the transistor is (1)
It is represented by a formula.

[0017]

[Equation 1] In the equation (1), k is Boltzmann's constant 1.38 × 10
^ -23 and T are absolute temperatures, and Is is the reverse saturation current of the transistor 20.

As shown in the equation (1), Vb is a bias point that is a constant voltage drop from VCC.

Although the present invention has been described using the NPN transistor, the present invention is not limited to this and can be replaced with an active element such as a MOS transistor or a MIS transistor which can realize a negative resistance.

[0020]

Since Vb can always be set to a voltage which is a constant voltage drop from Vcc, the two transistors 18 and 19 for generating a negative resistance supplied as a bias to the base electrode have their respective bases. , Emitter,
Even if the voltage between the collector terminals changes in VCC, it is always constant. Therefore, the circuit element that determines the frequency of the voltage controlled oscillation circuit does not fluctuate with respect to VCC, so that fluctuations in oscillation frequency with respect to the power supply voltage can be reduced. Further, since Vb is supplied from the so-called emitter follower circuit of the transistor 20, even if β of the transistor decreases and the base current of the transistors 18 and 19 increases, the fluctuation of the transistor occurs. Since the bias current can be supplied without lowering the voltage of Vb, a sufficient voltage is not given to the transistors forming the current sources 2 and 3, which has not been considered in the conventional circuit, and the occurrence of oscillation failure is eliminated. it can.

[Brief description of drawings]

FIG. 1 is a voltage controlled oscillator circuit according to the present invention.

FIG. 2 is a conventional voltage controlled oscillator circuit.

[Explanation of symbols]

1-3 ... Current source, 5-8 ... Resistor, 9, 10 ... Inductor, 11-15 ... Capacitor, 16, 17 ... Variable capacitance,
18 to 20 ... Transistor.

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 5J081 AA02 BB01 CC18 CC35 DD02                       DD11 DD24 EE02 EE03 EE18                       FF01 FF21 FF23 GG01 KK02                       KK09 KK22 LL05 MM01

Claims (5)

[Claims] 1. A power supply point, which is a terminal to which an inductor is connected, for a bias voltage of the transistor in a resonance circuit composed of an inductor and a capacitor and a transistor connected as a positive feedback circuit. An oscillating circuit that is supplied from a device that provides a constant voltage drop connected to the. 2. The oscillator circuit according to claim 1, wherein the transistor is a bipolar transistor having an NPN structure, and the base terminal and the collector terminal are commonly connected to the element for providing the constant voltage drop. 3. The oscillator circuit according to claim 1, wherein the transistor is a MOS transistor, and the element for providing the constant voltage drop has a source terminal and a drain terminal commonly connected. 4. Oscillation of a circuit type comprising two or more inductors having one terminal commonly connected, a capacitor and a negative resistance circuit connected to each inductor, and feeding power to a common connection point of the inductors. In the circuit, the negative resistance circuit is composed of a plurality of transistors, the collector of one transistor to the base terminal of the other transistor,
Each of them is connected via a capacitor, and the base of each transistor is connected via a resistor to the emitter terminal of a transistor whose collector terminal is connected to the common connection point of the inductor, and also via a current source. Oscillator circuit grounded. 5. The oscillator circuit according to claim 1, wherein the capacitance element can be made variable by a control signal.