JPS6062233A - Semiconductor switching device - Google Patents

Abstract

PURPOSE:To perform effective switching between a video and an audio signal by connecting plural switching circuits which each have a transistor (TR) for buffer amplification, forward polarity connection diode, reverse-polarity two-stage serial diodes, constant current source driving circuit, and switch to a common load. CONSTITUTION:An input signal is inputted from a terminal 1 to the base of an NPN TR2 and a buffer-amplified signal is inputted from its emitter to the anode of a diode 3. The output of the diode 3 is inputted to the cathode of a diode 4, whose output is inputted to the cathode of a diode 5, the anode output of which appears as an output signal at the connection terminal 8 of the constant current source circuit 9 of the common load. The TR2 and diodes 3-5 are driven by the constant current source circuit 6 from the connection point of the diodes 3 and 4, and the connection point is controlled externally by a switch 7. Further, plural switch circuits each including an output terminal 8 connected to the forward polarity side of a diode group of diodes 4 and 5 are provided and the circuit 9 is used as a common load.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention 8A is a video signal and audio signal used in television and radio transmission equipment. The present invention relates to a semiconductor switching device for switching.

As a recent semiconductor switching circuit, a switcher circuit is known in which a complementary transistor operates as an emitter follower and the bias voltage of both transistors is controlled by a switching transistor to turn all signals on and off. The connected multi-input switcher had the disadvantage that the transmission characteristics of differential gain (1)G) and differential phase (DP) deteriorated.

In order to improve such drawbacks, the inventor of the present invention
Although a complete semiconductor switching circuit was proposed in Japanese Patent Application No. 57-231615, this proposal also had problems such as limitations on the load of DC level fluctuations.

The purpose of the present invention is to eliminate these defects, completely suppress variations in switch characteristics, improve switching crosstalk characteristics,
It is an object of the present invention to provide a semiconductor switching device in which G, Dr characteristics and DC offset temperature dependence characteristics are all improved, and output DC levels are matched.

The structure of the semiconductor switching device of the present invention includes a transistor for fully buffering and amplifying a signal, a first diode connected to the emitter or source of this transistor in a forward polarity,
A second diode group in which two diodes of the same reverse polarity are connected in series to the reverse polarity side of the first diode, and a second diode group with one end connected to the connection point between these first diodes and the second diode group. A plurality of switching circuits including a connected constant current source circuit, a switch circuit which is fully connected at one end to the connection point and can be externally controlled, and a blade terminal connected to the forward polarity side of the second diode group, Each output terminal of the switching circuit is characterized in that it is commonly connected to a constant current source circuit serving as a common load and serves as an output terminal.

Hereinafter, the present invention will be explained in detail with reference to all the drawings.

FIG. 1 is a circuit diagram of an embodiment of the present invention. In the figure, an input signal is input from an input terminal l to the base of an NPN transistor 2, and a buffered and amplified output signal is taken out from the emitter of the transistor 2.

This output signal is input to the anode of a diode 3 connected to the emitter of the transistor 2 with forward polarity, the signal is fully output from the cathode of this diode 3, this output signal is input to the cathode side of the diode 4, and this output signal is input to the cathode side of the diode 4. An output signal is taken from the cathode of the diode 4, inputted to the cathode of the diode 5 connected to this anode with forward polarity, and connected to the constant current source circuit 9 of the common load connected to the anode side of the diode 5. The blade signal is obtained at the output terminal 8.

In such a configuration, transistor 2. diode 3
．． Diode 4. The diode 5 is driven by a constant current source circuit 6 from the connection point between the diode 3 and the diode 4. Also, what is the connection point?

It is externally controlled by the switch circuit 7 to turn on or off.

Furthermore, by connecting all the output terminals of a second switching circuit that is the same as this semiconductor switching circuit, and turning on all switch circuits 7 of the second switching circuit by external control), the diode is reverse biased, and the first A semiconductor switching device is obtained in which the first switching circuit is turned on and the second switching circuit is completely turned off.

As explained above, in this explanation, after the second switching circuit? It is clear that by providing a plurality of semiconductor switching devices, it is possible to construct an entire semiconductor switching device with multiple inputs and one output. Further, in the present invention, the transistor 2. Since two diodes 4.5 are provided corresponding to the switching circuit of diode 3, it is possible to match the DCC level to be operated.
It is clear that the cutting V% property is further improved.

In addition, in this embodiment, the case of NPN) 7 resistor was explained, but PNP) transistor or F E
It is clear that a similar circuit can be obtained by using T = i and considering the forward and reverse polarity.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of an embodiment of the present invention. In the figure, 1...signal input terminal, 2...NPN
) transistor, 3-4-5...diode,
6.9...constant current source circuit, 7...sui, tuna circuit, 8...output terminal.

Claims (1)

[Claims] A transistor that fully buffers and amplifies the signal, a first diode connected to the emitter or source of this transistor with forward polarity, and two diodes with the same opposite polarity connected to the opposite polarity side of this first diode. a second group of diodes connected in series;
To the connection point with the diode group -S4? ! - equipped with a plurality of switching circuits including a constant current source circuit connected thereto, a switch circuit that is connected at one end to the connection point and can be externally controlled, and an output terminal connected to the forward polarity side of the second group of diodes; A semiconductor switching device characterized in that each output terminal of these switching circuits is commonly connected to a constant current source circuit serving as a common load to serve as an output terminal.