JPH0823264A - Voltage controlled oscillation circuit - Google Patents

Abstract

PURPOSE:To improve lock characteristic of jitters or the like by providing a stable oscillation frequency by compensating a base current to be consumed by a delay amount control part by providing a voltage/current conversion circuit inside a ring oscillation voltage controlled oscillator circuit. CONSTITUTION:A ring oscillation voltage controlled oscillator circuit 10 adds voltage/current conversion circuits 12 equipped with base current correcting circuits 11 to current control terminals V2 at the differential parts of (n) stages of differential amplifiers 6. The circuit in Figure uses a Wilson's current mirror circuit composed of three transistors Q8, Q9 and Q10 and two resistors R1 and the current mirror circuit of a PNP transistor composed of two transistors Q13 and Q14 and two resistors R3. A voltage control terminal Vcont increases its impedance, and the oscillation frequency of the oscillator circuit 10 can be controlled only by the voltage. Even when the voltage/current conversion circuit 12 is connected to a current control terminal V1 at the emitter follower of the oscillator circuit 10, the similar effect can be provided.

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 can be applied to, for example, a voltage controlled oscillator circuit arranged in a PLL (Phase Locked Loop) circuit.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG.
It comprises a phase comparator 1, a charge pump 2, a lag lead filter 3 and a voltage controlled oscillator circuit 4. This PLL
The voltage controlled oscillator circuit 4 in the circuit 5 is an oscillator circuit capable of changing the oscillation frequency by controlling the voltage.

Here, the phase comparator 1 inputs the reference frequency fr from the outside of the PLL circuit 5 and the oscillation frequency fp output from the voltage controlled oscillation circuit 4, and compares the two phases. After that, the phase comparator 1 outputs an up signal or a down signal to the charge pump 2 according to the phase comparison result.

At this time, when the phase comparator 1 outputs an up signal, the charge pump 2 causes a current corresponding to the up signal to flow into the lag lead filter 3 and stores an electric charge (voltage) in the capacitance C in the lag lead filter 3. When the phase comparator 1 outputs a down signal, the charge pump 2
Draws out a current corresponding to the down signal from the lag lead filter 3 and reduces the electric charge (voltage) stored in the capacitance C in the lag lead filter 3. In this way, the voltage of the voltage control terminal Vcont of the voltage controlled oscillator circuit 4 is controlled. After that, the oscillation frequency fp output from the voltage controlled oscillator circuit 4 is locked to the reference frequency fr by the feedback loop.

Here, the voltage controlled oscillator circuit 4 is a voltage controlled oscillator circuit which self-oscillates by free discharge, or, as shown in FIG. 4, a differential amplifier 6 of n stages is fed back to cause self-oscillation and propagation. There is a ring oscillation type voltage control oscillation circuit 8 or the like in which the delay control circuit 7 controls each differential amplifier 6. The oscillation frequency of the ring oscillation type voltage control oscillation circuit 8 controls the amount of propagation delay (delay) at each stage by changing the current of the emitter follower of the differential amplifier 6 or the differential section by the propagation delay control circuit 7.

[0006]

By the way, the above-mentioned PL is used.
The voltage controlled oscillator circuit 4 arranged in the L circuit 5 includes
A ring oscillation type voltage controlled oscillator circuit 8 as shown in FIG. However, when the oscillation frequency fp of the PLL circuit 5 is locked to the reference frequency fr, the impedance of the current control terminal Vcont becomes high impedance,
Although there is no output current from the charge pump 2, since the base current flows through the transistor in the voltage controlled oscillator circuit 4, the electric charge (voltage) stored in the capacitor C in the lag lead filter 3 decreases, and the control voltage terminal Vcont There is a problem that the control voltage drops. Further, because of this, the oscillation frequency of the voltage controlled oscillator circuit 4 is not stable, so that there is a problem that a jitter or the like occurs and a stable locked state cannot be maintained.

The present invention has been made in consideration of the above points, and it is possible to output a stable oscillating frequency and stabilize the oscillating frequency to improve the lock characteristic of a jitter or the like. It is intended to propose a circuit.

[0008]

In order to solve such a problem, according to the present invention, a plurality of stages of differential amplifiers (6) and the amount of current flowing through the differential amplifiers (6) are increased or decreased to reduce the amount of propagation delay. A ring oscillation type voltage control oscillator circuit including a delay amount control unit (7) for controlling is provided between a voltage control terminal (Vcont) for giving a propagation delay amount and the delay amount control unit (7), and controls the delay amount. A current correction unit (12) that supplements the base current consumed by the unit (7) is provided.

[0009]

A ring oscillation type voltage control comprising a plurality of stages of differential amplifiers (6) and a delay amount control section (7) for controlling the propagation delay amount by increasing or decreasing the amount of current flowing through the differential amplifier (6). In the oscillator circuit, a voltage control terminal (Vco
nt) and the delay amount control unit (7), and a current correction unit (1) that supplements the base current consumed by the delay amount control unit (7).
By providing 2), a stable oscillation frequency can be output.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings.

1 and 2 shown with the same reference numerals as in FIG.
Shows the configuration of the ring oscillation type voltage controlled oscillator circuit 10. The ring oscillation type voltage control oscillation circuit 10 has a configuration in which a voltage / current conversion circuit 12 having a base current correction circuit 11 is added to the current control terminal V2 of the differential section of the n-stage operation amplifier 6.

The voltage / current conversion circuit 12 includes two current mirrors (current reflecting mirrors) and two transistors Q1.
It is connected with 1 and Q12. The current mirror has a circuit configuration in which a current is applied to the collector side of a transistor whose collector and base are short-circuited, and the collector and base terminals are connected to the base terminals of other adjacent transistors.

Here, three transistors Q8, Q9,
A Wilson current mirror consisting of Q10 and two resistors R1 and a PNP transistor current mirror consisting of two transistors Q13 and Q14 and two resistors R3 are used. The current mirror of the PNP transistor is provided as the base correction circuit 11 in order to supplement the current of the base current flowing through the transistor in the input stage of the differential amplifier. Also, two transistors Q11, Q
Currents from the transistors Q14 and Q13 respectively flow in the bases of 12. At this time, the transistor Q1
The current values flowing through the bases of 1 and Q12 are equalized by the current mirror of the PNP transistor. Further, since the collector currents of the transistors Q11 and Q12 flow through the transistors Q8 and Q10 in the Wilson current mirror, the transistors Q11 and Q12 are the same transistor so that the collector currents become equal.

In the above structure, since the transistor Q14 in the base current correction circuit 11 is a part of the current mirror, a current equal to the current flowing in the transistor Q13 flows. The currents from the transistors Q14 and Q13 flow to the bases of the transistors Q11 and Q12. The transistors Q11 and Q12 are the same transistor, and since the currents flowing to the bases are the same, the respective emitter currents are also the same. The increase / decrease in the base current of the transistor Q11 is 1 / H _FE (H _FE is the forward current amplification factor) of the collector current flowing in the transistor Q11, and this current is composed of the transistors Q8, Q9, Q10 and the resistor R1. Transistor Q with Wilson current mirror
The emitter currents of 8 and Q9 become equal.

Here, the base current flows through the transistors Q6 and Q7 in the input stage of the differential amplifier, and the current control terminal V2 for controlling the propagation delay amount of the differential amplifier.
Current is drawn from the side. This current control terminal V2 is voltage /
Since it is connected to the current conversion circuit 12, this circuit 12
Therefore, the base currents of the transistors Q6 and Q7 are subtracted from the current flowing through. The voltage control terminal Vcont has a high impedance, and current does not flow out or flow in. Therefore, the oscillation frequency of the ring oscillation type voltage controlled oscillator circuit 10 can be controlled only by the voltage.

According to the above configuration, by adding the voltage / current conversion circuit 12 having the base current correction circuit 11 to the current control terminal V2 of the differential section of the ring oscillation type voltage controlled oscillation circuit 10, the differential amplifier is provided. Since the base current consumed in the input stage is compensated by the base current correction circuit 11 in the voltage / current conversion circuit 12, a more stable oscillation frequency can be output.

In the above embodiment, the voltage / current conversion circuit 12 is connected to the current control terminal V2 of the differential section of the ring oscillation type voltage controlled oscillation circuit 10, but the present invention is not limited to this. Alternatively, the same effect can be obtained by connecting the voltage / current conversion circuit 12 to the current control terminal V1 of the emitter follower of the ring oscillation type voltage control oscillation circuit 10. In addition, the voltage / current conversion circuit 12 may be connected to the current control terminal V1 of the emitter follower of the ring oscillation type voltage control oscillation circuit 10 and the current control terminal V2 of the differential section.

Further, in the above-mentioned embodiment, the one using the current mirror of the PNP transistor as the circuit for correcting the base current has been described, but the present invention is not limited to this, and one capable of correcting the base current. If so, a circuit other than the current mirror of the PNP transistor may be used.

Although the ring oscillation type voltage controlled oscillator circuit 10 has been described in the above embodiments, the present invention is not limited to this and may be used in a PLL circuit having a voltage controlled oscillator circuit. Moreover, since the ring oscillator type voltage-controlled oscillator circuit 10 which is excellent in stability during locking, radio, or tuner portion of a television or the like, any frequency fully synchronized with the input frequency f _r by using a PLL circuit The same effect can be obtained by using it in a frequency synthesizer, a data clock recovery circuit for optical communication, etc.

[0020]

As described above, according to the present invention, a voltage / current conversion circuit having a base current correction circuit is provided in a ring oscillation type voltage controlled oscillator circuit, and a transistor in the ring oscillation type voltage controlled oscillator circuit is provided. By compensating for the base current consumed by, stable oscillation frequency can be output,
Locking characteristics such as jitter can be improved by stabilizing the oscillation frequency. Further, the time constant of the loop filter with respect to the noise band can be reduced, and the pull-in time can be shortened.

[Brief description of drawings]

FIG. 1 is a block diagram showing a ring oscillation type voltage controlled oscillator circuit according to an embodiment of the present invention.

FIG. 2 is a circuit diagram showing a ring oscillation type voltage controlled oscillator circuit according to an embodiment of the present invention.

FIG. 3 is a block diagram showing a basic structure of a PLL circuit.

FIG. 4 is a block diagram showing a conventional ring oscillation type voltage controlled oscillator circuit.

[Explanation of symbols]

1 ... Phase comparator, 2 ... Charge pump, 3 ... Lag lead filter, 4 ... Voltage controlled oscillator circuit, 5 ... PL
L circuit, 6 ... Differential amplifier, 7 ... Propagation delay control circuit,
8, 10 ...... Ring oscillation type voltage controlled oscillator circuit, 11 ......
Base current correction circuit, 12 ... Voltage / current conversion circuit, V
cont …… Voltage control terminal.

Claims (3)

[Claims] 1. A ring oscillation type voltage controlled oscillator circuit comprising a plurality of stages of differential amplifiers and a delay amount control section for controlling a propagation delay amount by increasing / decreasing a current amount flowing through the differential amplifiers. A voltage controlled oscillator circuit, comprising: a current correction unit provided between a voltage control terminal for giving a quantity and the delay amount control unit and compensating for a base current consumed by the delay amount control unit. 2. The voltage controlled oscillator circuit according to claim 1, wherein the current correction unit supplements a base current of a control unit that controls a current of a differential input stage of the delay amount control unit. . 3. The voltage controlled oscillator circuit according to claim 1, wherein the current correction unit supplements a base current of a control unit of the delay amount control unit that controls a current of an emitter follower output stage.