JPH0918296A - Oscillation circuit - Google Patents

Abstract

PURPOSE: To provide the oscillation frequency which can obtain a fixed oscillation frequency against the change of the ambient temperature. CONSTITUTION: This oscillation circuit is provided with a first transistor TR 3, a second TR 5, a third TR 6, a fourth TR 7, and a bias circuit 9 which gives a bias so as to make first and fourth TRs and second and third TRs alternately conductive in accordance with the output signal from a first load 1 and/or that from a second load 4. A limiter is provided which is provided with PN junction elements 23 and 26 and plural resistances 21 and 22 and divides the voltage generated from PN junction elements by plural resistances 21 and 22 and uses the divided voltage to limit the output signal level generated in the first load and/or the second load.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oscillating circuit using a multivibrator, and more particularly to an oscillating circuit capable of obtaining a constant oscillating frequency even when ambient temperature changes.

[0002]

2. Description of the Related Art An oscillation circuit using a multivibrator is known. Since an oscillator circuit using a multivibrator can be configured by using only a capacitor as an oscillator, it is optimal for making the oscillator circuit into an IC. As long as the capacitance value of the capacitor is about the same, it can be built in the IC.

FIG. 2 is a circuit diagram showing an oscillator circuit using such a multivibrator. The first transistor (3) has a collector connected to a first load (1) and an emitter connected to one end of a capacitor (2). ) And the collector is second
The emitter is connected to the load (4) and the emitter is the capacitor (2).
A second transistor (5) connected to the other end of the capacitor, a third transistor (6) having a collector connected to one end of the capacitor (2) and forming a current source, and a collector having the other end of the capacitor (2). A fourth transistor (7) that is connected to the above to form a current source, a fifth transistor (8) that supplies a constant current to the third or fourth transistor (6) (7), and the first load (1) And / or the first and fourth transistors (3) and (7) and the second and third transistors (5) and (6) are alternately turned on in response to the output signal of the second load (4). Bias circuit (9) for applying bias and output terminals (10) (11)
And

Next, the principle of oscillation will be briefly described.
It is assumed that the point A in FIG. 2 is at the “H” level and the point B is at the “L” level. Then, the potential on the emitter side of the transistor (12) rises and becomes "H" level as a whole.
Further, the potential on the emitter side of the transistor (13) is lowered and becomes "L" level as a whole.

Therefore, an "L" level voltage is applied to the bases of the first and fourth transistors (3) (7), and the bases of the second and third transistors (5) (6) are applied. An "H" level voltage is applied. When an "H" level voltage is applied to the bases of the second and third transistors (5) and (6), the current I flowing through the fifth transistor (8) that supplies a constant current flows through both transistors. It will be.

Then, the capacitor (2) is charged in the direction shown, and the emitter voltage of the second transistor (5) rises. When the emitter voltage of the second transistor (5) rises, the second transistor (5) turns off. Then, the voltage at the point B becomes the “H” level, the potential on the emitter side of the transistor (13) rises, and the voltage becomes “H” as a whole.
Level.

Then, the first and fourth transistors (3)
An "H" level voltage is applied to the base of (7), and the first and fourth transistors (3) and (7) are turned on. First
When the fourth transistors (3) and (7) are turned on, the point A
Voltage becomes "L" level, the potential on the emitter side of the transistor (12) decreases, and becomes "L" level as a whole.

Therefore, the capacitor (2) is charged in the opposite direction to the illustrated direction, and the same operation is repeated. That is, the first and fourth transistors (3)
(7) and the second and third transistors (5) and (6)
The bias circuit (9) operates so as to alternately conduct and, and as a result, an oscillation output signal is obtained at the output terminals (10) and (11).

The oscillation frequency F of the oscillation output signal obtained at the output terminals (10) and (11) is

[0010]

[Equation 2]

## EQU1 ## Where I is the constant current value of the fifth transistor (8), C is the capacitance value of the capacitor (2), and V is the amplitude of the signal generated in the first load (1) and the second load (4). Is. Therefore, according to the circuit of FIG. 2, it is possible to configure an oscillation circuit using a multivibrator.

[0012]

However, when the oscillation circuit of FIG. 2 is integrated into an IC, the oscillation frequency F fluctuates when the ambient temperature rises. In the circuit of FIG. 2, the element whose value fluctuates with temperature is VBE which is the PN junction voltage of a transistor or a diode.
There is resistance. The rate of each variation is as follows for each degree, and the change in the resistance value has a relatively greater effect.

VBE = −2.0 mV / ° C. R = + 0.15% / ° C. When the voltage of the reference power source (14) in FIG. 2 is VB, the PN junction voltage is VBE, and the resistance value of the resistor (15) is R3, The constant current value I of the fifth transistor (8) is

[0014]

(Equation 3)

## EQU1 ## In the equation (3), the change in the voltage VBE is larger than the change in the resistance R3, so that the value of the equation (3) increases as the temperature rises. Therefore, the fifth
The constant current value I of the transistor (8) increases. on the other hand,
Amplitude VPP of the signal generated in the second load (4) of equation (2)
Is determined by the current flowing through the second load (4) and is as follows.

[0016]

(Equation 4)

However, R5 is the resistance value of the second load (4). In the equation (4), the voltage VBE decreases as the temperature rises, so the amplitude VPP increases. As an example, VBE
Substituting = 0.7V and R3 = R5 = 500 ohms into equation (4), if there is a temperature change of 100 degrees, the change is as follows.

Normal temperature +100 degrees Specific current I 600 micro A 869 micro A + 45% Amplitude VPP 0.6V 1V + 66% As a result, the rate of increase of the amplitude VPP is larger than that of the current I. It gets smaller when it rises.

[0019]

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and includes a first transistor having a collector connected to a first load and an emitter connected to one end of a capacitor, and a collector having a second load. Connected to the other end of the capacitor, a second transistor connected to the other end of the capacitor, a collector connected to one end of the capacitor to form a current source, and a collector connected to the other end of the capacitor for the current source. So that the first and fourth transistors and the second and third transistors are alternately turned on in accordance with an output signal from the fourth transistor and the first load and / or the second load. In an oscillation circuit including a bias circuit for applying a bias, PN
A junction element and a plurality of resistors are provided, a voltage generated from the PN junction element is divided by the plurality of resistors, and the divided voltage is used to limit an output signal level generated in the first and / or the second load. The feature is that a limiter is provided.

[0020]

According to the present invention, in the multivibrator type oscillation circuit, a limiter for limiting the output signal level generated in the first and second loads is provided so that the amplitude of the oscillation output signal changes according to the temperature change. I have to. for that reason,
Even if the current value I that determines the oscillation frequency of the oscillation circuit fluctuates due to temperature, the amplitude V of the oscillation output signal works to suppress the change, so that the oscillation frequency of the oscillation circuit becomes constant as a whole. .

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an oscillator circuit of the present invention.
(20) is a resistor (21) (22), a transistor (2)
3) to (25) and a diode (26), which is a limiter for limiting the voltage level at points A and B.
In FIG. 1, the same circuit elements as those in FIG. 2 are designated by the same reference numerals and the description thereof will be omitted.

With respect to the current I1 flowing through the emitter of the transistor (23), when the value of the resistor (21) is R1 and the PN junction voltage of the transistor or diode is VBE,

[0023]

(Equation 5)

## EQU1 ## Then, set the value of the resistor (22) to R
2. When the power supply voltage is Vcc, the transistor (24)
The limiter voltage VL generated at the emitter of (25) is

[0025]

(Equation 6)

The voltage at points A and B does not drop below this voltage. When the voltage at the point A and the voltage at the point B can be expressed by the equation (6), the amplitude VPPL of the oscillation signal generated in the first load (1) and the second load (4) is

[0027]

(Equation 7)

## EQU1 ## In the equation (7), the resistance R1 is set to 6K ohms and the resistance R2 is set to 700 ohms.
Then, a positive coefficient is applied to the voltage VBE.
Further, since the fluctuations of the resistors R1 and R2 in the equation (7) due to the temperature change are canceled out, the fluctuation factor of the equation (7) is the voltage V
BE only. Under these conditions, the amplitude VPPL becomes smaller as the temperature rises. As the amplitude VPPL decreases, the oscillation frequency F of the oscillation output signal obtained at the output terminals (10) and (11) of the equation (2) increases.

Therefore, the oscillation frequency F becomes constant. At this time, the magnitude of the change of the voltage VBE depends on the resistances R1 and R1.
It can be arbitrarily changed by the ratio of 2. Specifically, equation (7)
The value of is substituted into the equation (2), the temperature is differentiated, and the ratio of the resistors R1 and R2 is set so as to be constant. In the equation (7), if the resistance R2 is set to be larger than that of the resistance R1, the voltage VBE has a negative coefficient. By doing so, when the temperature rises, the amplitude V
It is also possible to increase the PPL.

[0030]

As described above, according to the present invention, in the multivibrator type oscillation circuit, the limiter for limiting the output signal level generated in the first and second loads is provided, and the amplitude of the oscillation output signal is controlled by the temperature. Since the change is made according to the change, even if the current value I that determines the oscillation frequency of the oscillation circuit fluctuates due to temperature, the amplitude V of the oscillation output signal works to suppress the change. The oscillation frequency of the circuit is constant.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an oscillator circuit of the present invention.

FIG. 2 is a circuit diagram showing a conventional oscillator circuit.

[Explanation of symbols]

 (3) First transistor (5) Second transistor (6) Third transistor (7) Fourth transistor (9) Bias circuit

Claims (3)

[Claims] 1. A first transistor having a collector connected to a first load and an emitter connected to one end of a capacitor, and a second transistor having a collector connected to a second load and an emitter connected to the other end of the capacitor. A third transistor having a collector connected to one end of the capacitor to form a current source, a fourth transistor having a collector connected to the other end of the capacitor to form a current source, the first load and / or the second load An oscillating circuit including a bias circuit for applying a bias so as to alternately conduct the first and fourth transistors and the second and third transistors according to an output signal from the PN junction element and a plurality of PN junction elements. And dividing the voltage generated from the PN junction element by the plurality of resistors and using the divided voltage. Oscillating circuit, characterized in that a beauty or limiter for limiting the output signal level generated in the second load. 2. The oscillator circuit according to claim 1, wherein the reference voltage of the limiter is set so as to increase according to an increase in ambient temperature. 3. A first transistor having a collector connected to a first load and an emitter connected to one end of a capacitor, and a second transistor having a collector connected to a second load and an emitter connected to the other end of the capacitor. A third transistor whose collector is connected to one end of the capacitor to form a current source, a fourth transistor whose collector is connected to the other end of the capacitor to form a current source, and a constant current to the third or fourth transistor 5th to supply
A transistor, and a bias circuit for applying a bias so as to alternately conduct the first and fourth transistors and the second and third transistors in response to the output signals of the first load and / or the second load. , And the oscillation frequency F is Here, I is a constant current value of the fifth transistor, C is a capacitance value of the capacitor, and V is an amplitude of a signal generated in the first load and / or the second load. In the oscillation circuit defined by, a limiter for limiting the output signal level generated in the first and second loads is provided, and the amplitude V is changed by changing the amplitude V when the constant current value I fluctuates according to an increase in ambient temperature. An oscillation circuit characterized in that the oscillation frequency F is constant.