JP2660978B2 - Electronic switch circuit - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic switch circuit using a transistor as a non-contact switch, for example, an electronic switch used as a part of an electronic switching device in a television or a video tape recorder. It relates to a switch circuit.

2. Description of the Related Art In recent years, televisions and video tape recorders are equipped with an electronic switching device for variously controlling an image state and an audio state. For example, the switching device is operated by operating a remote control device or the like. Is operated.

The electronic switch circuit used in this type of switching device is configured by using a plurality of transistors as non-contact switches, and outputs a plurality of switching control signals for switching between an audio signal and a muting signal in a television, for example. Such a transistor is known, and utilizes a function in which a transistor is turned on / off by changing a base voltage with respect to an emitter.

[Problems to be Solved by the Invention] However, it is necessary to set and add each base voltage for accurately turning on / off a plurality of transistors accurately, and the voltage setting circuit requires special contrivance. is necessary.

In particular, in recent years, the number of electronic devices operated by a low-voltage power supply has been increasing from the viewpoint of miniaturization and low power consumption. In order to achieve this, an electronic switch circuit is required in which the circuit design tends to be complicated, the setting of the switching instruction voltage is simple, and the switching operation is reliably performed.

Furthermore, in recent electronic devices, circuits have been integrated as much as possible,
In particular, there is a tendency to use LSIs, and electronic switch circuits are required to have a circuit configuration suitable for the use of LSIs.

The present invention has been made under such circumstances, and an object of the present invention is to provide an electronic switch circuit in which setting of a switching instruction voltage is extremely simple and a reliable switching operation can be obtained.

[Means for Solving the Problems] In order to solve such problems, the present invention provides a first differential amplifier switch including a first transistor and a second transistor that operate on an input signal; A second differential amplifier switch including a third transistor and a fourth transistor operated by the first differential amplifier switch; a constant current source is connected to each of the second differential amplifier switches; And depending on the input signal level,
The third transistor or the fourth transistor operates, and one of the constant current sources operates.

[Operation] The present invention provided with such means can be determined by the first reference voltage of the first differential amplifier so as to be switched at a desired input signal level, and the switching level of the constant current source is Since the switching level is determined by the second reference voltage of the second differential amplifier, the switching level can be set more freely than in the conventional case.

Examples Hereinafter, the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing one embodiment of an electronic switch circuit according to the present invention.

The base of the transistor Tr ₁ is input signal V ₃ of GND～V _CC is input at an input terminal in Figure 1. Transistor Tr
₁ and Tr ₂ are differential amplifiers, and when the input signal V ₃ <reference voltage V ₁ , the transistor Tr ₁ operates, and the base of the transistor Tr ₃ Voltage. Transistor Tr ₃ and Tr ₄ are related base voltage by the differential amplifier is V ₂ <V _4.

That is, when V ₃ <V ₁ , Tr ₃ operates, and the current Io ₁ from the first current source is output. Next, when V ₃ > V ₁ , the transistor Tr ₂ operates, Becomes By keeping the relationship of V ₂ <V ₄ ′, when V ₃ > V ₁ , Tr ₄ operates and the current Io ₂ is output from the second current source.

[Effect of the Invention] As described above, according to the present invention, V ₁ for determining the input switching level is used.
It can be determined value and the value of V ₂ to determine the constant current source freely.

Therefore, the allowable value of the input voltage can be widened, and an accurate switch operation can be obtained even at a low voltage.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of an electronic switch circuit according to the present invention. Transistor Tr ₁ ...... first transistor transistor Tr ₂ ...... second transistor transistor Tr ₃ ...... third transistor transistor Tr ₄ ...... fourth transistor transistor Tr ₅ ...... fifth transistor transistor Tr ₆ ...... Sixth transistor Transistor Tr ₇ … Seventh transistor Transistor Tr ₈ … Eighth transistor Io ₁ … Current from the first current source Io ₂ …… Current from the second current source R ₁ , R ₂ … Tr ₃ bias resistor 1,2 …… Constant current source

Claims (1)

(57) [Claims] An input terminal, a first current output terminal, and a second current output terminal, wherein the first current output terminal and the second current output terminal are connected to each other according to a voltage applied to the input terminal. An electronic switch circuit for outputting a current from any one of the first and second differential amplifier switches having first and second transistors forming a differential pair, wherein a base of the first transistor is the input terminal. A first reference voltage is input to the base of the second transistor, and the second transistor performs an ON operation in accordance with a comparison result between the voltage supplied to the input terminal and the first reference voltage; A first differential amplifier switch that operates OFF, and third and fourth transistors that form a differential pair;
The base of the third transistor is connected to the second transistor, and the base of the fourth transistor is connected to the second transistor.
And a second differential amplifier switch to which a reference voltage of
The third transistor is turned off when the second transistor is turned on according to the comparison result with the reference voltage of
A second differential amplifier switch in which when the fourth transistor is turned on and the second transistor is turned off, a third transistor is turned on and the fourth transistor is turned off; A first current source that operates when the transistor is turned on and outputs a current to the first current output terminal;
An electronic switch circuit comprising: a second current source that operates when the fourth transistor performs an ON operation and outputs a current to the second current output terminal.