JPH0548418U - Double wave detection circuit - Google Patents

Abstract

(57) [Abstract] [Purpose] To realize a dual-wave detection circuit with high design flexibility and cost reduction. In a dual-wave detection circuit using a current mirror circuit in an output stage of a detection signal, at least one of voltage shift elements for equalizing collector voltages of two transistors forming the current mirror circuit is provided. Provided between the collector of the transistor and the output terminal.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a detection circuit, and more particularly to a double wave detection circuit that detects both positive and negative AC waves.

[0002]

[Prior Art]

 FIG. 2 is a circuit diagram showing the configuration of a conventional example of a double-wave detection circuit.

In the circuit shown in FIG. 2, an input circuit is composed of capacitors C21, C22, C23, resistors R21, R22, R23, R25, a coil L21 and a transistor Q21, and diodes D21, D22, D23, resistors R24, R26. , R27, R28, and transistors Q22, Q23, Q24, Q25 form a detection circuit.

Explaining the configuration of the input circuit, the emitter of the transistor Q21 is connected to the input terminal T21 via the resistor R21 and the capacitor C21, and is also connected to the −15V power source via the resistor R22. The base of the transistor Q21 is grounded via the resistor R23. The collector of the transistor Q21 is connected to the + 15V power source via the coil L21 and the resistor R25, and is also connected to the emitters of the transistors Q21 and Q22 via the capacitor C23. The midpoint between the coil L21 and the resistor R25 is grounded via the capacitor C22.

On the other hand, in the detection circuit, the respective emitters of the transistor Q23 and the transistor Q24 are connected to the + 15V power source through the resistors R26 and R27, respectively. The bases of the transistors Q23 and Q24 and the collector of the transistor Q23 are connected to the collector of the transistor Q22, and the collector of the transistor Q24 is connected to the output terminal T22. The emitters of the transistor Q22 and the transistor Q25 are connected to the capacitor C23. The base of the transistor Q22 is grounded via the capacitor C22, and the base of the transistor Q25 is grounded via the resistor R24. Three diodes D21, D23 and D22 are provided in the forward direction between the base of the transistor Q22 and the base of the transistor Q25. The collector of the transistor Q25 is connected to the output terminal T22, and the output terminal T22 is grounded via the resistor R28.

When an AC signal is input to the input terminal T21 of the double wave detection circuit, a waveform as shown in FIG. 3A in which the AC signal is amplified appears in the emitters of the transistors Q22 and Q25.

When an AC signal is input to each of the emitters of the transistor Q22 and the transistor Q25 that form the detection circuit stage, the transistor Q25 operates when the input is positive, and the transistor Q22 operates when the input is negative. In response to each of these operations, a current mirror circuit composed of a transistor Q23 and a transistor Q24 and operating as an output stage operates, and an input AC signal as shown in FIG. The detected waveforms of both waves appear.

In the above double-wave detection circuit, it is necessary to use transistors having the same characteristics as the transistors Q23 and Q24 that form the current mirror circuit so that the same collector current flows. However, the collector voltage of each transistor is different, and the collector loss and heat generation amount are also different. As a result, a temperature difference occurs between the transistors, and the characteristics of the transistors also differ, resulting in different collector current values flowing through the transistors.

For example, when resistors R26 and R27 having a resistance of 100Ω are used, respectively, a collector current of 5 mA flows through each transistor, and when a waveform of 1 V (PP) appears at the output terminal T22, the forward voltage drop is reduced to 0. When it is set to 0.6V, the collector voltage of the transistor Q23 becomes 13.9V. On the other hand, since the collector voltage of the transistor Q24 is set to about 1 V, the collector loss of each of the transistors Q23 and Q24 is about 3 mW and 68 mW, which causes a large difference in heat generation amount. Therefore, there is a difference in the time required for each transistor to reach a thermal equilibrium state, and during this period, the characteristics of each transistor (mainly VEB characteristics) differ and the output voltage becomes unstable. I will end up.

Conventionally, in order to reduce the rate of change in the characteristics of each transistor due to the difference in the amount of heat generation as described above, a transistor having a large heat capacity is used as a transistor forming a current mirror circuit, and the characteristics are sharp. It was prevented from changing to.

[0011]

[Problems to be solved by the device]

 In the conventional double-wave detection circuit described above, a transistor with a heat capacity larger than necessary is used in the current mirror circuit in order to keep the rate of change in the characteristics of each transistor small. However, there is a problem in that the degree of freedom in design is low and the cost is high.

The present invention has been made in view of the problems of the above-described conventional techniques, and it is assumed that the transistors forming the current mirror circuit have the same amount of heat generation and the degree of freedom in design is high. It is an object of the present invention to realize a dual-wave detection circuit that has high cost and can reduce cost.

[0013]

[Means for Solving the Problems]

 The double-wave detection circuit of the present invention is a double-wave detection circuit in which a current mirror circuit is used in the output stage of the detection signal, and the collector voltages of the two transistors forming the current mirror circuit are equal. Is provided between the collector and the output terminal of at least one of the transistors.

[0014]

[Action]

 By providing the voltage shift element, the collector voltages of the two transistors forming the current mirror circuit become equal, and therefore the collector loss and the amount of heat generated in each transistor become equal. Therefore, the time until each transistor reaches the thermal equilibrium state and the changing state of the characteristics during that time are similar, and the output voltage is always stable.

[0015]

【Example】

 Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing the configuration of an embodiment of the present invention.

Configurations and operations of the resistors R11 to R18, the capacitors C11 to C13, the diodes D11 to D13, the coil L11, the input terminal T11, the output terminal T12, and the transistors Q11 to Q15 in FIG. 1 are the same as those in the conventional example shown in FIG. The resistors R21 to R28, the capacitors C21 to C23, the diodes D21 to D23, the coil L21, the input terminal T21, the output terminal T22, and the transistors Q21 to Q25 are the same as those of the resistors R21 to R28.

In the present embodiment, a Zener diode ZD11 which is a voltage shift element is provided between the collector of the transistor Q14 and the output terminal T12.

The Zener diode ZD11 has a zener voltage VD of approximately 12V. As in the conventional example shown in FIG. 2, when resistors R16 and R17 of 100 Ω are used, a collector current of 5 mA flows to each transistor, and a waveform of 1 V (PP) appears at the output terminal T12, If the forward voltage drop is 0.6V, the collector voltage of the transistor Q13 will be 13.9V. On the other hand, since the collector voltage of the transistor Q14 is set to about 13 V because the Zener voltage VD is applied, the collector loss of each of the transistors Q23 and Q24 is about 3 mW, and the heat generation amount is almost equal.

In the present embodiment configured as described above, the heat generation amounts generated in the transistors Q13 and Q14 forming the current mirror circuit are substantially equal to each other. Since the characteristics of each transistor during the period and during this period were almost the same, the fluctuation of the output voltage could be suppressed.

In the present embodiment, the Zener voltage VD of the Zener diode ZD11 is described as ≈12V, but this value may be determined by the output voltage value, the values of the resistors R16 and R17, and the current value. It may be selected so that the collector voltages of the transistors forming the mirror circuit are almost equal.

Further, as the voltage shift element, the Zener diode is described as being provided between the collector of one transistor and the output terminal, but it is conceivable to use a transistor or the like as the voltage shift element. It is not particularly limited. Further, each transistor may be provided with an element having a different shift voltage to accurately adjust the collector voltage.

[0023]

[Effect of the device]

 Since the present invention is configured as described above, it has the following effects.

Since it is not necessary to use a transistor having a larger heat capacity than necessary as a transistor forming the current mirror circuit, there is an effect that the degree of freedom in design can be increased and the cost can be reduced.

[Brief description of drawings]

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

FIG. 2 is a circuit diagram showing a configuration of a conventional example.

3A and 3B are waveform charts showing the operation of the conventional example shown in FIG.

[Explanation of symbols]

 C11 to C13 Capacitor R11 to R18 Resistance D11 to D13 Diode Q11 to Q15 Transistor L11 Coil T11 Input terminal T12 Output terminal ZD11 Zener diode

Claims (1)

[Scope of utility model registration request] 1. A dual-wave detection circuit using a current mirror circuit in an output stage of a detection signal, wherein at least a voltage shift element for equalizing collector voltages of two transistors forming the current mirror circuit is provided. A double-wave detection circuit provided between the collector and the output terminal of one transistor.