JPS5922431A - Voltage controlled oscillation circuit - Google Patents

Abstract

PURPOSE:To make an input control voltage proportional to the frequency of an oscillated output, by changing a common emitter current of a pair of transistors(TRS) constituting a current switching circuit with a control voltage and supplying a collector current of one TR to a capacitor. CONSTITUTION:TRsQ1, Q2 constitute a differential amplifier, and the collector of the TRQ1 is connected to the base of the TRQ2 via a resistor R2. TRsQ3, Q4 constitute a current switching circuit, and the base and the collector of the TRQ3 are connected to a pin 3 together with the base of the TRQ1. One end of a capacitor C1 is connected to the pin 3. TRsQ5, Q6 form a current mirror circuit, which is connected to a power supply VB via resistors R3, R4. A control voltage VC is inputted from a pin 6 and an output F is obtained from the pin 2. When a voltage VP of the pin 3 is smaller than a voltage VA of a point A, the charging operation is made and when the VP is larger than the voltage VA, the discharge operation is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a voltage controlled oscillation circuit, and more particularly, to a voltage controlled oscillation circuit that can obtain an oscillation output according to an input control voltage.

[Technical background of the invention]

As shown in FIG. 1, a conventional voltage controlled oscillator circuit includes a first transistor QI and a second transistor Q! (Hereinafter, it will simply be referred to as a transistor, and the subscript numbers will be 1st, 2nd, etc.
) and a control voltage V. is input to bin 1 of the integrated circuit via terminal 6, resistor R+. Is the control voltage v0 input to bin 1 the transistor Q? , Q8. The on/off status of the transistors Q8 and Q4 whose emitters are connected in common is determined by the voltages P and v^ at the bin 3 and the point A. Transistor Q! by a current mirror circuit consisting of transistors Qll and Q6. A current mirror current is formed from the collector current of , and charges the capacitor CI connected to the bin 3. The oscillation output F is output from the collector of transistor Q2 via bin 2.

In the figure, transistors Q+o, Q++r, and Q+t constitute a constant current source, and transistors Q and Qlg constitute an output circuit. Also, bin 4 is a power supply v
B, pin 5 is connected to reference potential point G.

[Problems with background technology]

Frequency f of oscillation output F at pin 2 and control voltage V at pin 1 of the conventional voltage controlled oscillator circuit shown in FIG.

However, there is a relationship between V, the voltage vA at bin 3, the voltage a at point A, the proportionality constant Io, and the common emitter current as shown in equation (1), and the control voltage V. and the frequency f are not proportional, and the common emitter current factor. is the power supply v! +
Depends on. Therefore, when the control voltage V0 of pin 1 shown in Fig. 2 (4) is at the level V, , V, the switching time of the potential at point A becomes longer or shorter as shown in Fig. 2 (C)K. 2
As shown in Figure (B), the charging waveform at pin 3 will be distorted. Therefore, the frequency f of the P20 oscillation output F is also equal to the control voltage V of FIG. 2(4), as shown in FIG. 2(I)). It will not melt in proportion. Note that charging operation occurs when the voltage vP at pin 3 is smaller than the voltage vA at point A. In this case, transistors Qs and Qs are on, and transistor Q+ is on.
, Qt is turned off. When both voltages vP and vA are equal, they are inverted due to positive feedback. In discharging operation, the voltage ■P is vA
becomes larger, transistors Qi and Q+ are turned on, and transistor Q4+Q! is turned off. The charging time is transistor Q.

The discharge time is determined by the collector current of , the current mirror ratio of the transistors QlI and Qa, and the capacitance of the capacitor CI, and the discharge time is determined by the control voltage vc, the capacitance of the resistor R1, and the capacitor CI.

[Purpose of the invention]

The present invention has been made in view of the above points, and it is an object of the present invention to provide a voltage controlled oscillation circuit in which the input control voltage and the frequency of the oscillation output have an accurate proportional relationship.

[Summary of the invention]

The present invention provides a differential amplifier comprising a first transistor and a second transistor, one end of which is connected to the base of the capacitor. This differential amplifier operates as a positive feedback amplifier. Further, the third and fourth common emitter currents are changed by a control voltage. The third and fourth transistors constitute a current switching circuit.
The collector current of the transistor becomes a current mirror current and is supplied to the capacitor.

Therefore, the charging and discharging paths are the same and are exactly proportional to the control voltage.

[Embodiments of the invention]

An embodiment of the voltage control circuit according to the present invention will be described below with reference to FIG.

In Figure 3, transistors Q+ and Q! is a differential amplifier. In this differential amplifier, the collector of the transistor Q+ is connected to the base of the transistor Q+ via a resistor Rt.

Transistors Q1 and Q4 constitute a current switching circuit, and the base and collector of transistor Qa are connected to bin 3 together with the base of transistor Q+. Further, one end of a capacitor CI is connected to the bin 3, and the other end is connected to a reference potential point. The common emitters of transistors Q and Qa are connected to the collector of transistor Q8. Also, the base of transistor Q4 is at point A and transistor Q!
is connected to the collector of transistor Q++ along with the base of Q++.

Transistors Q and Q6 are current mirror circuits υ,
The base and collector of transistor QlI are both connected to the collector of transistor Q4. The emitter is connected to the power supply vB via a resistor R3. The emitter of transistor Q6 is connected to power supply VB via resistor R4, and the collector is connected to bin 3. Further, the base is connected to the base of transistor Q6.

The operation of the circuit will be explained below. Frequency f of transmission output F and control voltage V. However, there is a relationship between a and b as shown in the proportionality constant equation (2), and the frequency f and the control voltage v0 are proportional. Here, the voltage vP at pin 3 is the voltage V at point A
When A is smaller than A, charging operation is performed, and transistors Q8 and Ql are on, and transistors Q4 and C2 are off. The charging path is resistor R+, transistor Qf, Qs, Q+
Qs * Qs and pin 3. Voltage VP and vA
When they become equal, they are instantaneously reversed due to positive feedback. During discharge, transistor QspQ1 is on, transistor Q*
, Qt is turned off. In this case, the voltage vP is larger than the voltage ■. Is the discharge path through resistor R1 and transistor Q? .

Qs, Qi and pin 3. The voltages at each part in this case are shown in FIGS. Pin 1 shown in Figure 4
Control voltage ■. When the voltage decreases from V level to V level, as shown in FIG. 4(B), the period of the charging/discharging waveform of pin 3 increases in accordance with the decreased level. Since the charging and discharging times are exactly the same, there is no distortion in the waveform of the oscillation output F at pin 2, as shown in Figure 4).

The voltage controlled oscillation circuit according to the present invention is the first one. a positive feedback differential amplifier comprising a second transistor; a current switching means comprising a third and fourth transistor; and a fifth transistor forming a current mirror current from the collector current of the fourth transistor.
Since it is an elliptical structure including a current mirror circuit consisting of a sixth transistor, it has the advantage that one path related to charging and discharging can be formed by the current mirror circuit.

As a result, it is possible to obtain an oscillation output with a frequency proportional to the control voltage with completely equal charging and discharging times.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a conventional voltage controlled oscillation circuit, FIG. 2 is a time chart showing waveforms of each part of FIG. 1, and FIG. 3 is a circuit diagram of an embodiment of the voltage controlled oscillation circuit of the present invention. FIG. 4 is a time chart showing waveforms at various parts in FIG. In the figure, numerals 1 to 5 are pins, Qt to QIs are transistors, R1 to R4 are resistors, and C1 is a capacitor. Procedure Amendment f (spontaneous) Commissioner of the Japan Patent Office 1, Indication of the case, Patent Application No. 1237/1988 2, Name of the invention Voltage controlled oscillator circuit 3, Person making the amendment Relationship with the case Patent Applicant (307 ) Tokyo Shibaura Electric Co., Ltd. 4, Agent Address: 1-1-6 Uchisaiwai-cho, Chiyoda-ku, Tokyo 100 Tokyo Shibaura Electric Co., Ltd. Tokyo Office Detailed explanation of the invention in the specification Column 6, Contents of amendments (1) Description Correct the statement on page 3, line 8. (2) Similarly, "Charging waveform" on the 18th line of page 3 is corrected to "Charging/discharging waveform." (3) Similarly, on page 4, lines 5 and 6, “Transistor Qa + Ql is on, transistor Q 4 * Q
2 is off, J'tr) transistor Q a + Q 1 is off, transistor Q 41 Q 2 is on." (4) Similarly, on page 7, lines 4 to 6, change "Transistors Qa and Ql are on, transistors Q4 and Qz are off" to "Transistors Q3 and Ql are off, and transistors Q4 and Qz are on." Naru,” he corrected. (5) Figure 1 of the drawings will be corrected as shown in the attached sheet.

Claims (1)

[Claims] A positive feedback differential amplifier includes a first transistor and a second transistor, each of which has one end of the capacitor connected to its base; 3. A current switching means consisting of a fourth transistor, and a fifth transistor and a collector connected to one end of the capacitor to operate with the collector current of the fourth transistor in order to supply the collector current of the fourth transistor to the capacitor as a current mirror current. 1. A voltage controlled oscillator circuit comprising: a current mirror circuit including a sixth transistor, and configured to change an oscillation frequency in accordance with changes in a common emitter current.