JPS6267920A - Voltage controlled oscillator - Google Patents

Abstract

PURPOSE:To obtain an oscillator always oscillated by constituting a transistor (TR) connected just after a control voltage input terminal so as to be triggered for the application of power thereby preventing disabled oscillation of an astable multivibrator. CONSTITUTION:When a power is applied to a power terminal 16, a potential is applied to a collector of TRs 7, 8 constituting the astable multivibrator. A current passes through a capacitor 4 at the same time momentarily and a potential is generated across a resistor 5. Thus, the base voltage of the TRs 7, 8 in the astable multivibrator reaches a ground level and below the base- emitter saturation voltage thereby facilitating the oscillation of the astable multivibrator. When the power voltage is kept applied, the oscillation of the astable multivibrator is continued and a signal at a control voltage input termi nal 1 is the base voltage of the TRs 7, 8 through the resistor 3 and the oscilla tion frequency of the astable multivibrator is controlled.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is directed to (1) a voltage controlled oscillator used for example as a subcarrier oscillator, especially a state in which the oscillation operation that occurs when the voltage controlled oscillator is turned on (this can be referred to as (2) This is related to the prevention of oscillation (called inability to oscillate).

[Conventional technology]

FIG. 2 is a circuit diagram showing a conventional voltage controlled oscillator.
In the figure, (1) is the control voltage input terminal, (7+j(
8) is a transistor that constitutes an astable multivibrator, +91, tin is a transistor f71,
(Base resistance that limits the signal input to 81, u,
02 is a capacitor that determines the oscillation period, 01, a
4) is a transistor (7).

(8) is the collector resistor, al is the oscillation output terminal, and (18 is the power supply terminal).

A conventional voltage controlled oscillator is configured as shown in -1. Next, the operation will be explained. When power is turned on to the power supply terminal OQ, a potential is applied to the base of the transistor (7) or (8) due to noise when the power is turned on. At this time, the base voltage ■5 is the base-emitter saturation voltage vB
When EG is reached, the transistor is generally turned on. Let us assume that the transistor in the ON state is transistor (8).

The collector voltage vc2 of the transistor (8) is
The emitter saturation voltage becomes V. vc2 is “E to CF2”
8, the charge accumulated in the capacitor aυ is discharged. The base voltage V of the transistor (7) is lowered to -(power supply voltage vcc+vB88), and the transistor (7) is turned off. Here, since the transistor (8) is in the ON state, the capacitor Q3
is charged through the resistor (9) by a signal input from the control voltage input terminal fi+. Also, the capacitor aυ is V
is charged by By charging the capacitor 03, the base potential vb of the transistor (7) increases.

increases and becomes equal to ■. When K8 becomes equal to vB8s, the transistor (7) is turned on. When the transistor (7) is turned on, the collector voltage vc,
is V. 88, the capacitor a2 discharges the accumulated charge, and V2 drops to -("cc+"BFi8), thereby turning the transistor (8) off. Transistor (because the power is in the ON state).

Capacitor aO is charged across resistor ill by the input voltage. Capacitor G'IJ is also charged by V. By charging the capacitor a+), the voltage ``b2'' rises to ■BES, resulting in the initial state. By repeating this operation, the transistors (71, (8)).

Alternately turn ON, ○FF l, and perform self-excited photography. The self-excited vibration is outputted from the oscillation output terminal 4.

[Problem that the invention seeks to solve]

Conventional voltage controlled oscillators are configured as described above, so in order to ensure that the astable multivibrator oscillates, one of the two transistors that make up the astable multivibrator must be in the OFF state when the power is turned on. without changing the base voltage to the base-emitter saturation voltage vB
There was a problem that it was necessary to make it less than IJ.

This invention was made to solve the above-mentioned problems, and by making the base potential of the transistors forming the astable multivibrator lower than the base-emitter saturation voltage when the power is turned on, The object is to obtain a voltage controlled oscillator that can always start oscillation.

[Failure to solve the problem]

The voltage controlled oscillator according to the present invention is used to lower the base voltage of the transistors forming the astable multivibrator to be equal to or lower than the base-emitter saturation voltage when the astable multivibrator is powered on.

This makes it easy to start the astable multivibrator's oscillation by lowering the base voltage to the ground level only when power is input using the switching operation of the transistor.

[Effect]

The voltage controlled oscillator according to the present invention detects a signal when the power is turned on using a capacitor and a resistor, uses this as a trigger to turn on the transistor, and thereby sets the base voltage of the transistor constituting the astable multivibrator to the ground level. This makes it easy to start oscillation.

〔Example〕

FIG. 1 shows an embodiment of the invention. ill, f7
1 to (1 [9 is exactly the same as the above-mentioned conventional device.Hereinafter, embodiments of the present invention will be explained with reference to the figures.
In the figure, (2) is a transistor for switching, (3) is a resistor for protecting against overcurrent when the signal from the control voltage input terminal port is connected to the ground level by transistor (2), 4) is the power terminal θe
capacitor to detect when the power is turned on. (
5) is a resistor that converts the signal detected by the capacitor (4) into the Lami pressure, and (6) is the base resistor of the transistor (2).

In the voltage controlled oscillator configured as described above, the transistor (7) constitutes an astable multivibrator when power is applied to the power supply terminal -.

A potential is applied to the collector of (8). At the same time, an instantaneous current passes through the canopy (4) and a potential is generated in the resistor (5). This potential passes through the base resistor (6) and turns on the transistor (2). Transistor (2
) is turned on, the signal at the control voltage input terminal (9) goes to the ground level through the resistor (3). At the same time, the base voltages of transistors +71 and (8) in the astable multivibrator also go to ground level.
The base-emitter saturation voltage is below.

This facilitates the oscillation of astable multi-pipe rakes.

Next, if the power supply voltage remains on, the astable multivibrator continues to oscillate. Also, a capacitor (4
), the potential of the base of transistor (2) is at ground level, and transistor (2) is in an OFF state. For this reason.

Since the transistor (2) has a high resistance, the signal from the control voltage input terminal Il+ passes through the resistor (3) and directly becomes the base voltage of the transistors (7) and (8).

Since the oscillation frequency of the astable multivibrator can be controlled, the operation is then equivalent to that of the conventional voltage controlled oscillator described above.

〔Effect of the invention〕

As explained above, according to this invention,
The transistor connected immediately after the control voltage input terminal is configured to switch when the power is turned on as a trigger, which prevents the astable multivibrator from being unable to oscillate and ensures constant oscillation even if the control voltage is constantly input. It has the effect of giving you something.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing a voltage controlled oscillator according to an embodiment of the present invention, and FIG. 2 is a circuit diagram showing a conventional voltage controlled oscillator. In the figure (11 is the control ml + voltage input terminal, (2) is the transistor, (3) is the resistor, (4) is the capacitor, (5) is the
) is resistance. (6) is a resistor, (71, +8) is a transistor that constitutes an astable multivibrator, +91, αl is,
base resistance. υυ, 02 is an oscillation capacitor, CII, H is a collector resistor, Q injection is an oscillation output terminal, (1) is a power supply terminal. Note that the same reference numerals in each figure indicate the same or equivalent parts.

Claims (1)

[Claims] Connect an astable multivibrator using a transistor and the collector to the input terminal of this multivibrator,
A transistor with its emitter grounded, a resistor connected to the base of this transistor, a capacitor connected between this resistor and the power supply, a resistor connected between the above resistor and ground, the input terminal of the multivibrator and the collector of the above transistor. A voltage controlled oscillator with a resistor connected in series between the point where it is connected and the newly added input terminal.