CN100446420C

CN100446420C - Circuit device for eliminating signal leakage

Info

Publication number: CN100446420C
Application number: CNB2004100151243A
Authority: CN
Inventors: 谢明志
Original assignee: Hongfujin Precision Industry Shenzhen Co Ltd; Hon Hai Precision Industry Co Ltd
Current assignee: Hongfujin Precision Industry Shenzhen Co Ltd; Hon Hai Precision Industry Co Ltd
Priority date: 2004-01-10
Filing date: 2004-01-10
Publication date: 2008-12-24
Anticipated expiration: 2024-01-10
Also published as: CN1642007A

Abstract

The present invention relates to a circuit device for eliminating signal electric leakage, which comprises at least one circuit unit for eliminating electric leakage, wherein the circuit unit for eliminating electric leakage comprises a field effect transistor; the source electrode of the field effect transistor is connected with a signal line carrying the electric leakage, the gate electrode is connected with a direct current power supply in series by a resistor R1, the drain electrode is connected with the direct current power supply in series by a resistor R2 and the drain electrode outputs signal that the electric leakage is eliminated by an output terminal. The circuit device of the present invention can reduce expenses for eliminating leakage currents and guarantee that the functions of an original signal line and high-low quasi-positions can not be changed.

Description

The circuit arrangement that leaks electricity in the erasure signal

[technical field]

The present invention relates to the circuit arrangement that leaks electricity in a kind of erasure signal, particularly relate to a kind of field-effect transistor that adopts and come the circuit arrangement that leaks electricity in the erasure signal.

[background technology]

In Design of Digital Circuit, electric leakage (Electric Leakage) problem exists always, as shown in Figure 1, is the signal transmission schematic diagram that has electric leakage.Because have leakage current in A system 1, then it can send B system 2 to by transmission line, and these leakage currents can cause and have unnecessary noise in the signal of transporting to B system 2, or because the galvanomagnetic effect of electric leakage, and cause the misoperation of B system 2.

For eliminating these leakage currents, generally need to adopt custom-designed IC; The general purpose I C (as 7404 etc.) that perhaps is used for isolating electric leakage isolates electric leakage and keeps original signal.But, can cause waste so adopt IC to handle because the cost of IC is generally than higher, and need only isolate several electric leakage signal lines sometimes in design.

[summary of the invention]

In order to solve above-mentioned technical problem, the invention provides circuit arrangement simply a kind of and erasure signal electric leakage cheaply.The circuit arrangement that leaks electricity in this erasure signal, it can receive the signal that last system has electric leakage, and the signal that will eliminate electric leakage is transferred in next system, this circuit arrangement comprises: the circuit unit of at least one elimination electric leakage, and the circuit unit of this elimination electric leakage includes a field-effect transistor, an input, an output, one first resistance and one second resistance; Wherein, this input links to each other with the holding wire that one of last system has electric leakage, is used to receive the signal that has electric leakage; The source electrode of this field-effect transistor links to each other with input, and its grid is by this first resistance and a direct current power series, and its drain electrode is connected in series with this DC power supply by this second resistance; And the drain electrode of this field-effect transistor is connected with output, exports the signal of eliminating electric leakage to next system.

Wherein, it is identical to have the number of holding wire of electric leakage in the number of the circuit unit of erasure signal electric leakage and the last system.

Wherein, field-effect transistor is the MOSFET pipe, and its model is 2N7002, and the resistance of first resistance, second resistance is 8.2K Ω.

By circuit arrangement provided by the present invention, can reduce and eliminate the required expense of leakage current, and can guarantee that the function of original signal line and high low level can not be changed.

[description of drawings]

Fig. 1 is the signal transmission schematic diagram that has electric leakage.

Fig. 2 is an enforcement environment schematic diagram of the present invention.

Fig. 3 is the circuit theory diagrams that circuit is eliminated in electric leakage among Fig. 2 of the present invention.

[embodiment]

As shown in Figure 2, be enforcement environment schematic diagram of the present invention.In embodiment provided by the present invention, be an electric leakage elimination circuit 3 to be set eliminate between A system 1 and B system 2 from the electric leakage in the signal of A system 1.From the signal that has electric leakage that A system 1 is exported, through the effect of electric leakage elimination circuit 3, electric leakage wherein can be eliminated.

As shown in Figure 3, be the circuit theory diagrams that circuit is eliminated in electric leakage among Fig. 2.Adopt field effect transistor (Field-Effect Transistor in the present invention, FET) switching characteristic realizes the elimination of leaking electricity, rather than employing triode (Transistor), be because triode is the Flow Control assembly, if the employing triode then may produce misoperation because of the cause of leakage current.And field effect transistor is voltage-controlled assembly, so it is not influenced by the input of leakage current can.In an embodiment of the present invention, and employing metal oxide semiconductor field effect tube transistor (Metallic OxideSemiconductor Field-Effect Transistor, MOSFET).And the number of employed MOSFET pipe, determined by the line number signal that has electric leakage, the relation that it is identical with the line number signal that has electric leakage, promptly each MOSFET pipe can be eliminated the electric leakage on the signal line, when the holding wire increase that has electric leakage, needed MOSFET pipe increases thereupon.In an embodiment of the present invention, adopted two MOSFET pipes, the electric leakage of two holding wires has been eliminated.

MOSFET pipe in Fig. 3, note is made Q1 and Q2 respectively.The concrete annexation of this circuit is as follows:

Signal line from A system 1 links to each other with the source electrode (Source) of Q1 by input, and this holding wire has electric leakage.Can input to from the source electrode of Q1 the Q1 so have the signal of electric leakage, Q1 can eliminate action to these electric leakages.The grid of Q1 (Gate) links to each other with a direct current power supply (VCC) by a resistance R 1, and the drain electrode of Q1 (Drain) links to each other with VCC by a resistance R 2, and draws an output line from its drain electrode, and the signal of eliminating electric leakage is transferred to B system 2.Can be considered as a circuit unit of eliminating electric leakage to Q1 and connected resistance R 1 and resistance R 2.And the connected mode of the connected mode of MOSFET pipe Q2 and Q1 is similar.The source electrode of Q2 links to each other with another holding wire that has electric leakage from A system 1.The grid of Q2 links to each other with VCC by a resistance R 3, and the drain electrode of Q2 links to each other with VCC by a resistance R 4, and draws an output line from its drain electrode, and the signal of eliminating electric leakage is transferred to B system 2.In an embodiment of the present invention, Q1 and Q2 all adopt 2N7002 model MOSFET pipe, and the resistance of R1, R2, R3 and R4 is selected 8.2K ohm for use, and VCC is+5 volts.

Below concise and to the point its operation principle of narration.In this embodiment, the MOSFET pipe uses as switching tube, because the high input impedance of MOSFET pipe and voltage-controlled characteristic make the elimination electric leakage become possibility.With Q1 is example, and when the signal (from the A system) when be low level of input, then because the source electrode of Q1 is a low level, so voltage is greater than zero between the lock source of Q1, then Q1 is in conducting state, so the drain electrode of Q1 is output as low level, transfers to the B system; In like manner, when the signal of input when being high level, then because the source electrode of Q1 is a high level, so voltage is less than zero between the lock source of Q1, then Q1 is in cut-off state, thereby the drain electrode of Q1 is output as high level (+5 volts), transfers to the B system.The operation principle of Q2 is identical with Q1.Because the MOSFET pipe has voltage-controlled characteristic, the signal that transfers to the B system is only relevant with the voltage of original signal, and irrelevant with the electric current of original signal, the leakage current in the original signal can not transfer in the B system by the MOSFET pipe, so eliminated the electric leakage in the original signal.And accurate position and original function that circuit 3 can not change original signal are eliminated in this electric leakage.

The above-mentioned one embodiment of the invention that only provide wherein also can be selected the field effect transistor of other type for use.Wherein the number of MOSFET pipe depends on the number of the holding wire that has electric leakage, and is not only limited to two; The selection of the model of Q1 and Q2 and R1～R4 resistance can be adjusted according to actual conditions, but needs to guarantee to make Q1 and Q2 work on off state.

Claims

1. the circuit arrangement that leaks electricity in the erasure signal, it can receive the signal that last system has electric leakage, and the signal that will eliminate electric leakage is transferred in next system, it is characterized in that this circuit arrangement comprises:

The circuit unit of at least one elimination electric leakage, the circuit unit of this elimination electric leakage includes a field-effect transistor, an input, an output, one first resistance and one second resistance; Wherein: this input links to each other with the holding wire that last system one has electric leakage, is used to receive the signal that has electric leakage; The source electrode of this field-effect transistor links to each other with input, and its grid is by this first resistance and a direct current power series, and its drain electrode is connected in series with this DC power supply by this second resistance; And the drain electrode of this field-effect transistor is connected with output, exports the signal of eliminating electric leakage to this next system.

2. the circuit arrangement that leaks electricity in the erasure signal as claimed in claim 1 is characterized in that, the number of holding wire that has electric leakage in the number of the circuit unit of erasure signal electric leakage and the last system is identical.

3. the circuit arrangement that leaks electricity in the erasure signal as claimed in claim 2 is characterized in that, field-effect transistor is the MOSFET pipe.

4. the circuit arrangement that leaks electricity in the erasure signal as claimed in claim 3 is characterized in that, MOSFET pipe model is 2N7002.

5. the circuit arrangement that leaks electricity in the erasure signal as claimed in claim 4 is characterized in that, the resistance of first resistance, second resistance is 8.2K Ω.

6. the circuit arrangement that leaks electricity in the erasure signal as claimed in claim 1 is characterized in that, DC power supply is+5 volts.