JPH0787319B2 - Amplifier circuit - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an amplifier circuit with a switch that can very easily cut off a motor drive current or a large-current audio signal.

[Background technology]

Japanese Patent Application Laid-Open No. 12380 / 52-12 discloses an electronic circuit having the following circuit configuration. That is, the amplifier for input signal amplification, the complementary transistor whose base is driven by the output of this amplifier, and the current setting impedance connected to the emitter of this complementary transistor are combined, and the output current from both collectors of this complementary transistor is combined. It is an electronic circuit designed to be obtained.

The present inventor has made various technical studies on the electronic circuit as described above from the viewpoint of cutting off the output current as necessary. As a result, in order to cut off the output current supplied to the load, a mechanical switch such as a relay switch may be simple, but it is expensive, and the electronic device using the switch is expensive, which is not preferable. I realized that.

[Object of the Invention]

An object of the present invention is to provide an amplifier circuit with a switch, which is obtained by modifying / developing the electronic circuit as described above, and can control passage or non-passage of an output current supplied to a load by a switch means having a small current capacity. is there.

The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

[Outline of Invention]

To briefly describe the outline of the invention disclosed in the present application,
It is as follows.

That is, a switch means is provided on the input side of a current mirror circuit that obtains an output current n times as large as the input current, and a small current input side current is connected / disconnected by opening / closing this switch means. The object of the present invention of simply controlling is achieved.

〔Example〕

FIG. 2 is a circuit diagram of an amplifier circuit with a switch according to an embodiment of the present invention. In the following, for reference, the reference example of FIG. 1 will be described first before describing the embodiment of FIG.

Features of the amplifying circuit with a switch reference example shown in FIG. 1 is in contact disconnects the input current of the current mirror circuit 1 by the switch SW, the load of the output current Iout of the high current which is amplified by n times R _L
It controls the passage and non-passage to.

That is, the control voltage V _C is supplied to the base of the transistor Q ₁ that performs voltage-current conversion. Resistor R ₁ is a switch SW
Is turned on, the current mirror circuit 1
Is to determine the amount of the input side current I ₁ of. The current mirror circuit 1 is composed of a diode Q ₂ and a multi-emitter transistor Q _3, and has an output current Io.
ut is amplified to I ₁ · n.

According to the above circuit configuration, by switching the switch SW to the open state, the current path of the input current I ₁ of a small current is cut off, the output current Iout of a large current cannot be obtained, and the output current to the load R _{L is} not output. Iout is not passed.

Further, by switching the switch SW to the closed state, the input side current I ₁ flows and the large output current Iout passes through the load R _L.

Therefore, since the switch SW connects and disconnects the input side current I ₁ of a small current, the switch SW may be extremely low cost and simple, and the production cost of the electronic device using the switch SW can be significantly reduced. The switch SW is not limited to a mechanical switch, and an electronic switch may be used.

Next, the embodiment shown in FIG. 2 will be described.

The amplifying circuit with switch shown in this embodiment is composed of a semiconductor integrated circuit, and circles enclosing numbers are external connection terminals.

The feature of this embodiment resides in that push-pull amplification can be performed for the input signal Vin, and connection / disconnection control of the output voltage Vout is performed via the voltage-current conversion resistor _RA .

That is, when the input signal Vin is supplied while the switch SW is switched to the closed state, the output voltage V _D amplified by the operational amplifier 10 is obtained, but the amplification degree is the resistance Rf ₁ ,
It is determined by the ratio of Rf ₂ . Now suppose that the output voltage V _D
Is the positive polarity illustrated by the white background, the voltage
V _A becomes a voltage level determined by V _A = V _D + V _F Q ₁₁ , and the base current is supplied to the transistor Q ₁₄ via the constant current circuit CS ₁ . The transistor Q ₃₄ operates in the ON state, and the current I ₁₁ flows through the diode Q ₁₃ that forms the current mirror circuit 21. Since the diode Q ₁₃ and the transistor Q ₁₇ forming the current mirror circuit 21 are multi-emitters, the output current Iout _A of I ₁₁ · n proportional to the emitter area is output.
Is supplied to the load R _L via the output capacitor C ₁ .

On the other hand, if the output voltage V _D has the negative polarity illustrated by the black background, the voltage V _B becomes V _B = V _A −V _F Q ₁₂ and the transistor Q
_A bias voltage is supplied to ₁₅ to operate it in an on state, and a current I ₁₂ flows through a diode Q ₁₆ forming the current mirror circuit 22. Diode Q ₁₆ and current mirror circuit
Since the transistor Q ₁₈ constituting 22 is a multi-emitter, the output current Iout _B of I ₁₂ · n proportional to the emitter area flows through the load R _L.

By the way, if you want to cut off the output currents Iout _A and Iout _B ,
Turn off the switch SW. In this case, one end of the resistor R _A is opened, the current paths of the currents I ₁₁ and I ₁₂ are cut off, and neither of the output currents Iout _A and Iout _B can be obtained. Therefore, by cutting off the small currents I ₁₁ and I ₁₂ , the passage of the large current output currents Iout _A and Iout _{B to} the load R _L ,
Non-passage can be controlled.

FIG. 3 is a circuit diagram of the second reference example.

The feature of the second reference example is that the current amount of the input side current I ₂₁ of the current mirror circuit 1 is the current I _1N supplied from the current source 31.
It is in the point of being controlled by.

That is, the switch SW is provided for the same purpose as in the first reference example, and the current I _1N is set to a desired current value instead of the resistor R ₁ . Therefore, when the switch SW is on, the output current Iout _A becomes I ₂₁ · n. In the second reference example as well, by connecting and disconnecting the input current I ₂₁ having a small current, passage or non-passage of the output current Iout having a large current to the load R _L can be controlled.

〔effect〕

(1) By connecting / disconnecting the input side current path of the small current on the input side of the amplifying means which performs 1: n current amplification, the output side current of the large current can be controlled, and the above connection / disconnection is performed. The effect of reducing the cost of the switch means is obtained.

Although the invention made by the inventor has been specifically described based on the embodiments, the invention is not limited to the above embodiments, and various modifications can be made without departing from the scope of the invention. Needless to say.

For example, the switch SW may be either a mechanical switch or an electronic switch.

In addition to the current mirror circuits 1, 11 and 12, other transistors may be replaced with MOSFETs.

Further, although two power supplies are used in the embodiment, one power supply may be used. In this case, one end of the resistor R _A is Apply the voltage of EP.

[Field of application]

In the above description, the present invention made mainly by the present inventor has been described with respect to a switch non-amplifying circuit which is a field of use which is the background of the present invention, but the present invention is not limited thereto.

For example, it can be used for a motor drive circuit and an audio device. In addition, it can also be used for industrial electronic devices that control high power.

[Brief description of drawings]

FIG. 1 shows a circuit diagram of an amplifier circuit with a switch showing a basic technical idea as a first reference example, and FIG. 2 shows a concrete circuit diagram of an amplifier circuit with a switch which is an embodiment of the present invention. FIG. 3 is a circuit diagram of an amplifier circuit with a switch which is a second reference example. 1,11,12 …… Current mirror circuit, I ₁ ,, I ₁₁ ,, I ₁₂ ,, I ₂₁ ……
Input side current, Iout, Iout _A , Iout _B ...... Output current, Q ₁ , Q ₃ , Q
₁₄ , Q ₁₅ , Q ₁₇ , Q ₁₈ …… Transistor, Q ₂ , Q ₁₃ , Q ₁₆ …… Diode, _RL …… Load, 10 …… Operational amplifier.

Claims (1)

[Claims] 1. An input signal is received by each base electrode,
The first and second transistors of different conductivity types whose respective emitter electrodes are connected to each other, and the first transistor connected between the collector electrode of the first transistor and the first terminal of one polarity of the power source. A first diode to which a forward current is applied by the collector current of the first diode and its conductivity type to the same conductivity type as that of the second transistor, and a base-emitter bias voltage thereof is applied to the first diode by a terminal voltage of the first diode. It is connected between a first current mirror circuit including a multi-emitter transistor and a collector electrode of the second transistor and a second terminal of the other polarity of the power supply, and a forward current is given by the collector current of the second transistor. The second diode and its conductivity type are the same conductivity type as the first transistor, and A second current mirror consisting of a second multi-emitter transistor whose base-emitter bias voltage is given by the terminal voltage of the diode and whose collector is connected to the output terminal together with the collector of the first multi-emitter transistor. A circuit and a resistor and switch means connected in series between a common emitter electrode of the first and second transistors and a ground potential point, and output to the output terminal by the switch means. An amplifier circuit characterized in that the output current is controlled by a switch.