CN1068739C

CN1068739C - Signal switching circuit

Info

Publication number: CN1068739C
Application number: CN 95105568
Authority: CN
Inventors: 郑雅安; 张茂权
Original assignee: Acer Computer Co Ltd
Current assignee: BenQ Corp
Priority date: 1995-05-31
Filing date: 1995-05-31
Publication date: 2001-07-18
Anticipated expiration: 2015-05-31
Also published as: CN1137200A

Abstract

The present invention relates to a signal switching circuit which comprises a first analog switch transistor, a first exchange transistor, a transistor, a second analog switch transistor and a second exchange transistor, wherein a first signal source is input into the base electrode of the first analog switch transistor; the collecting electrode of the first exchange transistor is connected with the base electrode of the first analog switch transistor by a resistor and an exchange signal is input into the base electrode of the first exchange transistor; the exchange signal is input into the base electrode of the transistor; a second signal source is input into the base electrode of the second analog switch transistor; the collecting electrode of the second exchange transistor is connected with the base electrode of the second analog switch transistor by a resistor and the base electrode is connected with the collecting electrode of the transistor; the emitting electrodes of the first analog switch transistor and the second analog switch transistor are mutually connected into an output terminal which outputs the first or the second signal source for the exchange signal.

Description

A kind of signal switching circuit

The present invention especially refers to avoid a kind of signal switching circuit of signal source phase mutual interference about a kind of signal switching circuit.

General monitor has two signalling channels usually at present, can accept signal source of different nature.

As shown in Figure 1, one monitor 11 links with a PC 13 and workstation1 5 simultaneously, to monitor 11, and workstation1 5 output BNC higher frequency signals 151 are to monitor 11 than low frequency signal 131 for PC 13 output DSB, and PC 13 links with networking 153 with workstation1 5.

As shown in Figure 2, a work station 21 reaches monitor 23 with its literal than low frequency (TEXT) data-signal by DSB holding wire 211, and figure (GRAPHICS) data-signal of its higher-frequency is reached monitor 23 by BNC holding wire 213.

No matter be the pattern of Fig. 1 or Fig. 2, monitor all is to accept the user to select to show DSB or BNC signal from the switching of monitor panel.

The technology of knowing, shown in the DSB and BNC commutation circuit of Fig. 3 red (RED) rifle, the switching of the microprocessor (not shown) of monitor output DBBNC signal 35 these circuit of control.When DBBNC signal 35 is 0V, transistor Q193 is by (CUTOFF), Q192 is saturated, and the base stage of Q100 and Q102 is about 0.8V, the current potential of diode D1 negative pole end is higher than the current potential of positive terminal, thus D1 for opening circuit, the base stage of Q100 is 1.8V, the emission of Q100 is 2.5V very, and Q100 is action (ACTIVE).On the other hand, the current potential of D2 negative terminal is lower than positive terminal potential, and D2 is a path, and the base potential of Q102 is promoted to 3.5V, and Q102 is for ending.The vision signal of BNC signal 31 inputs this moment is exported to the video circuit of next stage by R O/P holding wire 37.

Otherwise when DBBNC holding wire 35 was 5V, the vision signal of DSB holding wire 33 inputs was exported to the video circuit of next stage by R O/P holding wire 37.

The circuit of labor Fig. 3, we find because of capacity effect and stray capacitance between the collector among Q100, the Q102, base newspaper, to have the generation of interference (CROSSTALK) situation when two channel B NC and DSB have the high frequency video signal.For example monitor can produce the picture that disturbed by the BNC signal when display channel is DSB.Otherwise monitor can produce the picture that disturbed by the DSB signal when display channel is BNC.

The present invention seeks at the problems referred to above, a kind of a kind of signal switching circuit of avoiding the mutual interference of signal source phase is provided.

That is a kind of signal switching circuit provided by the invention comprises:

One first analog switch transistor, its tool base stage, emitter, collector electrode, base stage is imported first signal source in the AC coupled mode;

One first switching transistor, its tool base stage, emitter, collector electrode, the transistorized base stage of collector electrode mat one resistance and first analog switch links, and signal is switched in base stage input one;

One transistor, its tool base stage, emitter, collector electrode, base stage is imported described switching signal;

One second analog switch transistor, its tool base stage, emitter, collector electrode, base stage is imported the secondary signal source in the AC coupled mode;

One second switching transistor, its tool base stage, emitter, collector electrode, the transistorized base stage of collector electrode mat one resistance and second analog switch links, and base stage and aforementioned transistorized collector electrode link;

Wherein, the first analog switch transistor and the transistorized emitter of second analog switch connect to output mutually, and signal switching circuit is exported first signal source or secondary signal source in response to switching signal.

Purpose of the present invention, feature and advantage will be elaborated in conjunction with the accompanying drawings by embodiment.

Brief Description Of Drawings

Fig. 1 discloses a monitor and is connected with a PC and work station respectively.

Fig. 2 discloses a monitor and a work station links and input BNC and DSB signal.

Fig. 3 discloses the commutation circuit of knowing.

Fig. 4 discloses commutation circuit of the present invention.

As shown in Figure 4, signal switching circuit of the present invention comprises: one first analog switch transistor Q100, one first switching transistor Q101, a transistor Q193, one second analog switch transistor Q102, one second switching transistor Q108.

The first analog switch transistor Q100 tool base stage, emitter, collector electrode, base stage is imported first signal source 41 in AC coupled (ac coupled) mode.

The first switching transistor Q101 tool base stage, emitter, collector electrode, the base stage of collector electrode mat one resistance R and the first analog switch transistor Q100 links, and base stage is imported a DBBNC switching signal 45.

Transistor Q193 tool base stage, emitter, collector electrode, base stage is imported described DBBNC switching signal 45.

The second analog switch transistor Q102 tool base stage, emitter, collector electrode, base stage is imported secondary signal source 43 in the AC coupled mode.

The second switching transistor Q108 tool base stage, emitter, collector electrode, the base stage of collector electrode mat one resistance R and the second analog switch transistor Q102 links, and the collector electrode of base stage and aforementioned transistor Q193 links.

The emitter of the first analog switch transistor Q100, the second analog switch transistor Q102 connects to R O/P output 47 mutually, and signal switching circuit is exported first signal source 41 or secondary signal source 43 to R O/P holding wires 47 in response to the DBBNC switching signal.

The magnitude of voltage in first signal source 41 or secondary signal source 43 is between 0 to 0.7 volt, and promptly the peak is to being 0.7V between peak value (peak to peak).

The first analog switch transistor Q100 and the second analog switch transistor Q102 are NPN transistor.

BNC signal 41 is output as example when being 0V with DBBNC switching signal 45 below, and effect of the present invention is described.

When DBBNC signal=0V, Q193, Q101 open circuit, the Q100 conducting, the Q108 conducting makes the base voltage of Q102 equal 0.2V, Q102 opens circuit, vision signal on the Q102 base stage is attenuated to 0.2V, can effectively the vision signal on the DSB passage 43 be decayed to 0.2V by 0.7V, makes the interference of 43 pairs of BNC signals 41 of this noise reduce to minimum.

Otherwise, when DSB signal 43 was exported when DBBNC switching signal 45 was 5V, can effectively the vision signal on the BNC passage 41 be decayed to 0.2V by 0.7V, make the interference of 41 pairs of DSB signals 43 of this noise reduce to minimum.

Claims

1, a kind of signal switching circuit comprises:

One first analog switch transistor (Q100), it has base stage, emitter, collector electrode, and this base stage is imported first signal source (41) in the AC coupled mode, and this collector electrode is connected with power supply;

One first switching transistor (Q101), it has base stage, emitter, collector electrode, and this collector electrode links by resistance and the transistorized base stage of first analog switch, and signal (45), this grounded emitter are switched in this base stage input one;

One transistor (Q193), it has base stage, emitter, collector electrode, and this base stage is imported described switching signal, and this collector electrode is connected with power supply;

One second analog switch transistor (Q102), it has base stage, emitter, collector electrode, and this base stage is imported secondary signal source (43) in the AC coupled mode, and this collector electrode connects power supply;

One second switching transistor (Q108), it has base stage, emitter, collector electrode, and this collector electrode links by resistance and the transistorized base stage of second analog switch, and the collector electrode of this base stage and described transistor (Q193) links, this grounded emitter;

Wherein, the first analog switch transistor and the transistorized emitter of second analog switch connect to output mutually, and signal switching circuit response switching signal is exported first signal source or secondary signal source to holding wire (47).

2, signal switching circuit as claimed in claim 1, wherein, the magnitude of voltage in first signal source or secondary signal source is between 0 to 0.7 volt.

3, signal switching circuit as claimed in claim 1, wherein, the first analog switch transistor and the second analog switch transistor are NPN transistor.