JPH09294019A - Oscillation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an oscillation device which has an ALC(automatic level control) function to set the output signal of an oscillator at a fixed level by controlling this signal level according to the output signal of a DC amplifier. SOLUTION: The emitters of the 1st and 2nd transistors TR 12 and 13 are connected in common to each other, and the output signals of phases opposite to each other are applied to the bases of both TRs from an oscillator. A capacitor 14 is charged by the signals produced at the common emitters of the TR 12 and 13. A 1st bias circuit 16 applies the bias to the TR 12 and 13 according to the output voltage of a voltage source 15, and a 2nd bias circuit 17 operates based on the output voltage of the source 15. Then the emitters of the 3rd and 4th TR 19 and 20 of a DC amplifier 18 are connected in common to each other, and the output voltage of the capacitor 14 is applied to the base of the TR 19 with the output voltage of the circuit 17 applied to he base of the TR 20 respectively. Thus, the output signal level of the oscillator is controlled according to the output signal of the amplifier 18.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ALC (automatic level control) for making the output signal level of an oscillator constant.
The present invention relates to an oscillator device having a function, and particularly to an oscillator device suitable for IC integration.

[0002]

2. Description of the Related Art A for keeping the output signal level of an oscillator constant
As an oscillator having an LC function, the device shown in FIG. 2 can be considered. The oscillator (1) in FIG. 2 has an oscillation loop inside and generates an oscillation output signal at the output terminal (2).
The oscillation output signal level of the oscillator (1) changes according to the control signal level of the control terminal (3).

In the initial state, the control signal level of the control terminal (3) is "L" level, and the oscillation output signal level thereof is high. This oscillation output signal is applied to the detection diode (7) through the DC blocking capacitor (4) and the DC voltage setting resistors (5) and (6). The diode (7) charges the capacitor (8) with the level-detected signal. Then, this charging voltage is applied to the positive input terminal of the DC amplifier (9). The voltage from the variable reference power source (10) is applied to the negative input terminal of the DC amplifier (9).
In the initial state, the setting is performed with an offset so that the voltage of the negative input terminal becomes high. Therefore, "L" level is generated at the output terminal of the DC amplifier (9). Therefore, the above-mentioned initial state is set.

From this state, when the oscillation output signal level increases, the charging voltage of the capacitor (8) gradually increases,
The level of the output terminal of the DC amplifier (9) becomes "H" level. Therefore, the oscillation output signal level stops increasing at a certain level and maintains that level. Therefore, according to the circuit of FIG. 2, an oscillation device having an ALC function for making the output signal level of the oscillator constant can be obtained.

[0005]

However, there is a problem that the circuit shown in FIG. 2 is not suitable for being integrated into an IC. First
In addition, in the circuit of FIG. 2, it is necessary to perform accurate level comparison by the DC amplifier (9), but it is difficult to generate an accurate error voltage because the two input signals have different temperature characteristics. There was a problem. PN inside the oscillator (1)
Temperature fluctuations in the junction voltage are particularly problematic.

Secondly, the DC blocking capacitor (4) is used in FIG. 2 in order to perform the level comparison as accurately as possible, but the use of the DC blocking capacitor (4) increases the chip area when integrated into an IC. There was a problem of inviting.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned points, and a first and a second oscillators in which an oscillator and an emitter are commonly connected to each other and output signals having mutually opposite phases are applied to a base. A second transistor, a capacitor charged by a signal generated in the common emitter of the first and second transistors, a current source, and a bias for biasing the first and second transistors according to the output of the current source. A first bias circuit, a second bias circuit that operates based on the output of the current source, and an emitter that are commonly connected to each other and an output voltage of the capacitor is applied to the base.
A direct current amplifier comprising a transistor and a fourth transistor to which the output voltage of the second bias circuit is applied, and the level of the output signal of the oscillator is adjusted according to the output signal of the direct current amplifier. It is characterized by

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of an oscillator according to the present invention, in which (11) is an oscillator and (12) (1).
3) The first and second emitters are commonly connected to each other and output signals of opposite phases of the oscillator are applied to the bases.
A transistor, (14) is a capacitor charged by a signal generated in the common emitter of the first and second transistors (12) and (13), (15) is a voltage source, and (16) is an output voltage of the voltage source. Accordingly, a first bias circuit for applying a bias to the first and second transistors (12) and (13), a (17) second bias circuit that operates based on the output voltage of the voltage source, and a (18) emitter A third transistor (19) commonly connected to each other and having an output voltage of the capacitor (14) applied to its base, and a fourth transistor having an output voltage of the second bias circuit (17) applied to its base.
A DC amplifier including a transistor (20).

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. The oscillator (11) in FIG. 1 is composed of a multivibrator using a differential amplifier. The two output signals of the differential amplifier show the same amount of change even when there is a temperature change. Then, the resistor (21) forming the first bias circuit (16)
The resistance value of (22) is set equal. Voltage source (1
A constant current flows through the constant current source (23) according to the voltage of 5). The constant current flows through the resistor (24) and the resistor (25), and voltage is generated at the points A and B, and the first bias circuit (1
6) and the second bias circuit (17). The voltage from point A passes through the resistors (21) (22) to the first and second
Bias is applied to the transistors (12) and (13).
Further, the voltage from the point B is supplied to the second bias circuit (17).

Since the resistance values of the resistors (21) and (22) are set to be equal, the first and second transistors (12) (1)
The base voltage of 3) becomes equal. Point C and point D in FIG.
The DC levels are equal to each other, and AC signals having mutually opposite phases appear. The signal is applied to the first and second transistors (12).
Full-wave rectification is performed at (13) and the capacitor (14) is charged.

On the other hand, the DC signal at the points C and D is divided into a resistance ratio by the resistors (21) and (22) and the resistor (25) to change the voltage at the point A. Therefore, if the DC signals at points C and D fluctuate due to temperature fluctuations, the voltage at point A also fluctuates according to the resistance ratio. The fluctuation voltage of the DC signal at the point C and the point D is the first and second transistors (12) and (13).
And via the capacitor (14) to the base of the third transistor (19). The fluctuating voltage causes the control signal level of the control terminal (3) to malfunction. Therefore,
In the present invention, the variable voltage is also applied to the base of the fourth transistor (20).

That is, at the point A, a voltage in which the fluctuating voltage is attenuated by the resistance ratio is generated. So the resistance (25)
If the resistance ratio is set so that the value of A becomes relatively large, the voltage fluctuation close to the DC signal fluctuation at the points C and D is reflected at the point A.
Can be generated at any time. Then, the voltage obtained by adding the offset voltage at the resistor (24) to the voltage at the point A is supplied to the second bias circuit (17). The offset voltage is determined by multiplying the current value of the constant current source (23) and the resistance value of the resistor (24).

As a result, a DC amplifier (18) having a third transistor (19) and a fourth transistor (20)
Thus, the voltage fluctuations are canceled out. The voltage at the point C passes through the PN junction voltage of the first transistor (12) once,
Applied to the base of the transistor (19). On the other hand, the voltage from the point B is applied to the base of the fourth transistor (20) once through the PN junction voltage of the transistor (26). Therefore, there is no PN junction voltage fluctuation due to temperature fluctuation between points C and D and the control terminal (3).

Therefore, according to the circuit of FIG. 1, the adverse effect of the PN junction voltage fluctuation due to the temperature fluctuation can be significantly reduced. Due to the function of the resistor (24), the base voltage of the third transistor (19) is lower than the base voltage of the fourth transistor (20) in the initial state. Therefore, the third transistor (19) is turned off, and no current flows through the control terminal (3). Therefore, the oscillation level of the oscillator (11) increases to. Then, the charging voltage of the capacitor (14) increases, and the third transistor (19) turns on.
Then, the oscillation level of the oscillator (11) does not become large at a certain level and stabilizes.

Therefore, according to the circuit of FIG.
An oscillator having a function can be obtained. Although the capacitor (14) is arranged in the description of FIG. 1, it may be omitted. When the frequency of the oscillation output signal of the oscillator (11) is high, it can be charged by the emitter capacitance of the first and second transistors (12) and (13). A resistor may be used instead of the constant current source (23) shown in FIG. In this case, the fluctuating voltage generated at the point A is
Since the voltage is divided by 4), the transmission efficiency deteriorates. If the point A and the points C and D are set to the same DC voltage, the fluctuating voltage can be efficiently extracted.

[0016]

As described above, according to the present invention, two signals having mutually inverted phases are taken out from the oscillator, and full-wave rectification is performed by the differential type circuit. Therefore, the detection efficiency is good and the value of the rectifying capacitor can be reduced. Further, according to the present invention, since the differential input of the DC amplifier can be obtained using the same bias circuit as a reference, the temperature characteristic of the oscillation output signal is good and the variation is small. Therefore, there is no need to regenerate the direct current in the IC, and a direct current blocking capacitor is not required, which is suitable for IC implementation.

[Brief description of drawings]

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

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

[Explanation of symbols]

 (11) Oscillator (12) First transistor (13) Second transistor (16) First bias circuit (17) Second bias circuit (18) DC amplifier

Claims (2)

[Claims] 1. An oscillator, a first and a second transistor to which emitters are connected in common, and output signals of opposite phases of the oscillator are applied to a base, and a common emitter of the first and second transistors. A capacitor charged by a signal, a current source, a first bias circuit that biases the first and second transistors according to the output of the current source, and a second bias that operates based on the output of the current source. A direct current amplifier having a third transistor having an emitter commonly connected to each other and having a base to which the output voltage of the capacitor is applied; and a base having a fourth transistor to which the output voltage of the second bias circuit is applied. An oscillator, wherein the level of the output signal of the oscillator is adjusted according to the output signal of the DC amplifier. 2. An oscillator, first and second transistors to which emitters are commonly connected, and output signals of opposite phases of the oscillator are applied to the base by DC coupling, and a common emitter of the first and second transistors. A capacitor charged by a signal generated in the current source, a current source, a first bias circuit for biasing the first and second transistors according to the output of the current source, and an operation based on the output voltage of the current source DC amplifier including a second bias circuit, a third transistor having emitters commonly connected to each other and a base to which the output voltage of the capacitor is applied, and a fourth transistor having a base to which the output voltage of the second bias circuit is applied. And an offset voltage set so that the base voltage of the fourth transistor is higher than the base voltage of the third transistor. And a preparative means, oscillator being characterized in that to adjust the level of the output signal of the oscillator in response to the output signal of the DC amplifier.