JPH09200001A - Voltage controlled oscillator circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To change continuously an oscillating frequency of a oscillation circuit by providing a voltage converter circuit that converts a received control voltage into a voltage whose variable range is within an unsaturation region of a transistor(TR) for control. SOLUTION: The voltage controlled oscillator circuit is made up of an input circuit for a control voltage given to the gate of a control P-channel TR 21 and provided with a resistor voltage divider circuit consisting of resistors 22, 23 that divide a voltage between a control voltage input terminal 24 and a fixed voltage input terminal 25 to provide the divided voltage to the gate of the control P-channel TR 21. The resistance of the resistors 22, 23 is decided properly for each TR being a component of the oscillator circuit. Then the variable range of the received control voltage is set within the unsaturation region of the TR 21. Thus, the oscillating frequency is continuously changed over the variable range of the control voltage.

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 capable of changing an oscillation frequency by changing a control voltage.

[0002]

2. Description of the Related Art FIG. 2 shows, as a conventional voltage controlled oscillator circuit, a circuit composed of a ring oscillator composed of three stages of inverters. In the figure, the ring oscillator section includes three P-channel transistors (hereinafter, referred to as “Pc
1 and 3, and 5 and three N-channel transistors (hereinafter, abbreviated as “Nch-Tr”) 2, 4, and 6. Pch-Tr1 and Nch-
Tr2, Pch-Tr3 and Nch-Tr4, and Pc
Three sets of h-Tr5 and Nch-Tr6 constitute respective inverters.

Reference numeral 7 is a fixed voltage side Pch-Tr, and 8 is a control voltage side Pch-Tr. Nch-Tr
9 and 10 form a Carrent Miller. Similarly, Pch-Trs 11 and 12 also constitute a Carrent mirror. Pch-Trs 13 and 14, and Nch-Trs 15, 16 and 17 are transistors for controlling the current flowing through each inverter of the ring oscillator. The capacitors 18, 19 and 20 are
This is for determining the delay value of the ring oscillator.

In the voltage controlled oscillator circuit having the above-mentioned structure, an inverter composed of Pch-Tr1 and Nch-Tr2, an inverter composed of Pch-Tr3 and Nch-Tr4, and Pch-Tr5 and Nch-Tr6.
A ring oscillator composed of a three-stage inverter of the inverter composed of oscillates. The oscillation frequency of this ring oscillator is determined as follows.

The current flowing between the drain and source of the fixed voltage side Pch-Tr 7 and the control voltage side Pch-T
The sum of the current flowing between the drain and source of r8 is Nch
-Flow to Tr9. The current flowing between the drain and source of Tr8 is controlled by the control voltage applied to the gate of Tr8. Since Tr9 forms a current mirror with Tr10, an equivalent current flows in Tr10, and the current also flows in Pch-Tr11 for use. Tr1
Since 1 composes a Prentch-Tr12 and a current mirror, an equivalent current flows through Tr12. And
Tr12 for Pch-Tr13 and 14 for current control
Currents proportional to the size ratio with (11) respectively flow. Similarly, a current proportional to the size ratio with Tr10 (9) flows through the Nch-Trs 15, 16 and 17 for current control.

In this way, the current values flowing through the inverters formed by Tr1 and 2, the inverters formed by Tr3 and 4, and the three-stage inverters formed by Tr5 and 6, respectively, and the delay capacitor 18,
The values of 19 and 20 determine the oscillation frequency. Each of the capacitors 18, 19 and 20 determines the delay time of each stage as the load capacity of the inverter of each stage forming the ring oscillator.

Therefore, the oscillation frequency changes by changing the control voltage, which is the gate voltage of the control voltage side Pch-Tr 8, to change the current flowing through each inverter of the ring oscillator. Further, by changing the set value of the fixed voltage which is the gate voltage of the fixed voltage side Pch-Tr7, the value of the current flowing through each inverter of the ring oscillator also changes, so that the oscillation frequency differs even with the same control voltage. . That is,
It is possible to obtain a plurality of oscillation frequency vs. control voltage characteristics using the fixed voltage, which is the gate voltage of the fixed voltage side Pch-Tr 7, as a parameter.

[0008]

The conventional voltage controlled oscillator circuit as described above has the control voltage side Pch-Tr8.
In the non-saturation region, the oscillation frequency can be changed by changing the control voltage which is the gate voltage of Pch-Tr8. However, Pch-T
In the cut-off region and saturation region of r8, Pch-
Even if the gate voltage of Tr8 is changed, the oscillation frequency cannot be changed. On the other hand, when such a transmission circuit is viewed from the outside as a black box, it is preferable that the transmission frequency continuously changes, preferably linearly, in the variable range of the control voltage applied to the transmission circuit.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a voltage controlled oscillator circuit in which the above-mentioned conventional problems are improved and the oscillation frequency continuously changes over the entire variable range of the control voltage applied to the oscillator circuit. And

[0010]

A voltage controlled oscillator circuit according to the present invention includes a ring oscillator including a plurality of stages of inverters, and a control transistor for changing an oscillation frequency by controlling a current flowing through each inverter. An input terminal for a control voltage applied to the control transistor and a fixed voltage input terminal for setting an operating parameter of the control transistor, wherein the control voltage input terminal and the control transistor are provided. In between, a voltage conversion circuit for converting the input control voltage so that the variable range thereof falls within the non-saturation region of the control transistor is provided.

With such a configuration, the oscillation frequency can be continuously changed over the entire variable range of the control voltage without requiring an additional circuit outside the oscillation circuit. Various known circuits can be used as the voltage conversion circuit, but as the simplest preferable circuit example, the voltage between the control voltage input terminal and the fixed voltage input terminal is divided to control the control circuit. It can be configured by a resistance voltage dividing circuit applied to the transistor for use.

[0012]

1 is a circuit diagram of a voltage controlled oscillator circuit according to a preferred embodiment of the present invention. In the figure,
The same circuit elements as those in the conventional example shown in FIG. 2 are designated by the same reference numerals. The ring oscillator consisting of three stages of inverters and the circuits around it are exactly the same as in the conventional example of FIG.

The voltage-controlled oscillation circuit according to the present invention shown in FIG. 1 differs from the conventional example shown in FIG. 2 in that a control Pch-Tr is used.
It is an input circuit of the control voltage given to the gate of 21. That is, the resistor 2 for dividing the voltage between the control voltage input terminal 24 and the fixed voltage input terminal 25 and applying it to the gate of the control Pch-Tr 21.
A resistive voltage divider circuit consisting of 2 and 23 is provided.
Accordingly, the fixed voltage side Pch in the conventional circuit of FIG.
-Tr7 has been deleted. By appropriately determining the values of the resistors 22 and 23 in accordance with the characteristics of each transistor constituting the oscillator circuit, the variable range of the input control voltage falls within the non-saturation range of the control Pch-Tr 21. The oscillation frequency can be continuously changed over the entire variable range of the control voltage.

Instead of the resistance voltage divider circuit as described above, the control voltage is converted by a voltage conversion circuit such as an OP amplifier so that its variable range falls within the non-saturation region of the control transistor. Good.

[0015]

As described above, the voltage controlled oscillation circuit according to the present invention does not require an additional circuit outside the oscillation circuit,
The oscillation frequency can be continuously changed over the variable range of the control voltage.

[Brief description of drawings]

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

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

[Explanation of symbols]

1,3,5 P-channel transistor of ring oscillator section 2,4,6 N-channel transistor of ring oscillator section 9,10 N-channel transistor for current mirror 11,12 P-channel transistor for current mirror 12, 13, 14 Current limiting P-channel transistor 15, 16, 17 Current limiting N-channel transistor 18, 19, 20 Delay capacitor 21 Control P-channel transistor 22, 23 Voltage divider resistor 24 Control voltage Input terminal 25 fixed voltage input terminal

Claims (2)

[Claims] 1. A ring oscillator including a plurality of stages of inverters, a control transistor for changing an oscillation frequency by controlling a current flowing through each inverter, and an input terminal for a control voltage applied to the control transistor. A voltage-controlled oscillation circuit having a fixed voltage input terminal for setting an operating parameter of the control transistor, wherein a control voltage input between the control voltage input terminal and the control transistor is A voltage controlled oscillator circuit comprising a voltage conversion circuit for converting the variable range so that the variable range is within the non-saturation region of the control transistor. 2. The resistance voltage dividing circuit according to claim 1, wherein the voltage conversion circuit divides a voltage between the control voltage input terminal and the fixed voltage input terminal and applies the divided voltage to the control transistor. Voltage controlled oscillator circuit.