How P-N Junction Diode Is Work In Reverse Biasing ?

When the P-region or Anode of the diode is connected to the negative terminal of the external DC source and N-region or Cathode of the diode is connected to the positive terminal of the external DC source. At that time we can say that the Diode is in "Reverse Biased" condition.

The Reverse Biased condition is indicated in the Fig.15a.

 
                                                         Fig.15a

When a diode is reverse biased, holes in the p-regions are attracted towards the negative terminal of the external DC supply and electrons in the n-regions are attracted towards the positive terminal of the external DC supply.

Due to movements of electrons and holes away from the junction, "the width of the depletion region increases". This happens due to the creation of the more numbers of immobile ions.

Due to more numbers of immobile ions opposite the junction, "the barrier potential will increase".

We know that the p-region consists of a small number of electrons and n-region consists of a small number of holes. These minority charge carriers get some thermal energy and crossed the junction and produce some current.

This current is know as "Reverse Saturation Current" Which indicated in Fig.15b.

                                                         Fig.15b

 

The End.

 

Also look out;

Post-13 Biasing Of A P-N Junction Diode(With External Bias)

Post-14 How P-N Junction Diode Is Work In Forward Biasing ?



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How P-N Junction Diode Is Work In Forward Biasing ?

When the P-region or Anode of the diode is connected to the positive terminal of the external DC source and N-region or Cathode of the diode is connected to the negative terminal of the external DC source. At that time we can say that the Diode is in "Forward Biased" condition.

The Forward Biased condition is indicated in the Fig.14a.

 
                                                               Fig.14a

When the Diode is in Forward biased condition, the free electrons from n-side are pushed towards the p-side. Similarly the holes from p-sides are pushed towards the n-side.

With increase in the external supply voltage V, more and more number of holes and electrons start traveling towards the junction.

Thus the holes will start converting the negative ions into the neutral atoms and the electrons will start converting the positive ions into the neutral atoms. Therefore we can say that "the width of the Depletion Layer or Region will reduce".

Due to reduction in the depletion region width, the barrier potential will also reduce. Then At a particular value of V the Depletion region will collapse. There are no traveling of holes and electrons.

                                                             Fig.14b

The large number of majority carrier crossing the junction produces a current called as the "Forward Current" which indicated in the Fig.14b.

The End.


Also look out;

Post-15 How P-N Junction Diode Is Work In Reverse Biasing ?

Post-13 Biasing Of A P-N Junction Diode(With External Bias)

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Biasing Of A P-N Junction Diode (With External Bias)

When the P-N Junction is formed, the depletion region gets created and movement of electrons and holes stops. Thus the current flowing through an unbiased P-N Junction is zero.

To make current to flow we have to Bias the P-N Junction Diode. Biasing is the process of applying external DC voltage to the semiconductor diode.

When the external voltage is not applied to the diode, the P-N Junction will remain in the state of equilibrium. Therefore there is no current flowing through it.

To make the current to flow, it is necessary to "Bias" the diode. The biasing can be two types;

[1] Forward Bias

To know how diode work in this condition, visit below post;

Post-14 How P-N Junction Diode Is Work In Forward Biasing ?

[2] Reverse Bias

To know how diode work in this condition, visit below post;

Post-15 How P-N Junction Diode Is Work In Reverse Biasing ?


Also look out below post;

Post-8 Formation of P-N Junction Diode(Without External Bias)




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How To Interface 5x7 Led Dot Matrix Segment By AT89C51 ?

Simply to explain the working principle of our 5x7 Led Dot Matrix Panel we introduced the one block/segment operation of this 5x7 Led Dot Matrix Panel. Thus we will understand the functionality of different Integrated Circuits pins and how different logic are passing through that pins. We also observed the decorder/demultiplexer‘s and octal buffer/line driver‘s logic variation at instant of time in simulation.

 

The simple Proteus simulation block diagram of this is as shown in Fig.12a

 Fig.12a

Here we used the common anode 5x7 Led Dot Matrix Module. Thus we applied the +Vcc or high logic to the row and ground or low logic to the column of 5x7 Led Dot Matrix Module. 

In Micro-controller we used Port0 as a selection of column to providing ground or logic low and Port2 providing data bus to the row of 5x7 Led Dot Matrix Module. 

For that concept we make the data code of the character ‘A’ which write as below.

             Unsigned array column = {0x7Eh, 0x7Dh, 0x7Bh, 0x77h, 0x6Fh}

             Unsigned array row = {0x81h, 0xF6h, 0xF6h, 0xF6h, 0x81h}

When micro-controller is sending the 0x7Eh data at Port0 at that time micro-controller is also sending 0x81h data at Port2. This both data are synchronized to each other. This are Shown in Fig. This synchronization is always in same manner to all five data of the array.

 Fig.12b

The 0x81h data is provided to the transistor switching circuit. When we applied 0 at the base terminal at that time the transistor will work as a switch. 

It means the collector voltage is applied is directly available to the emitter pin and through that it reach at the row pins of the 5x7 Led Dot Matrix Module. The working of the transistor as a switch is shown in Fig.12c

Fig.12c

Also the connection diagram of 5x7 Led Dot Matrix Modules to the Micro-controller through the transistor is as shown in Fig.12c 

In the 5x7 Led Dot Matrix Modules, one led dot consumes 10ma current. Therefore the whole segment having 350(35x10ma) current is required. There is a problem now because the micro-controller is not provided that much current therefore do not interface to the 5x7 Led Dot Matrix Module directly.

 Fig.12d

Thus we used one Line driver which driven the 5x7 Led Dot Matrix Modules’ columns. Here we used 74HC541 octal buffer/line Driver which is connected to the micro-controller’s Port0 and 5x7 Led Dot Matrix Modules’ columns which are shown in Fig.12d.

The c language program of display one character in the 5x7 Led Dot Matrix Modules is write below;

Program of display only one character in the 5x7 Led Dot Matrix Segment

#include

Void delay_ms ( int time );

Void main (void)

    {

       P1=0xFF;

       P2=0xFF;

    While (1)

        {

           P1=0x01;

           P2=0x01;

           delay_ms (1);

           P1=0x02;

           P2=0xEE;

           delay_ms (1);

           P1=0x04;

           P2=0xEE;

           delay_ms (1);

           P1=0x08;

           P2=0xEE;

          delay_ms (1);

          P1=0x10;

          P2=0x01;

         delay_ms (1); 

       }

}

Void delay_ms ( int time )

        {

         int i , j;

         for ( i=0; i

             for ( j=0; j<1275 font="" j="">

        }

The End.


Also visit below Post;

Post-10 Create A Character With Row Scanning Method In The LED Dot Matrix Display

Post-11 Create A Character With Column Scanning Method In The LED Dot Matrix Display




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Create A Character With Column Scanning Method In The LED Dot Matrix Display

Basic use of Led dot Matrix Module is used to display character in different different way. For that, How to generate a character in this segment? This is simple and first question raises in our mind.

If we talking about the generating character in Module, we satisfied the law of “Persistence of Vision”. In that law, our eye is detect the static character when at a time 1/16 different frames are moving in the segments. It means that the character display on the segment it is not steady in that one but it is scanning rows or column in segments.

Way of Scanning Techniques

There are some useful techniques by which we can done software multiplexing in 5x7 Led Dot Matrix Module. These are classifying in two methods which names as follows:

                      [1] Row Scanning Method
                      [2] Column Scanning Method

[2] Column Scanning Method

Suppose we want to display the alphabet A in the common anode 5x7 led dot matrix segment. We will first select the column C1 (which means C1 is pulled low in this case), and deselect other columns by blocking their ground paths (one way of doing that is by pulling C2 through C5 pins to logic high). 

Now, the first column is active, and you need to turn on the LEDs in the rows R2 through R7 of this column, which can be done by applying forward bias voltages to these rows. Next, select the column C2 (and deselect all other columns), and apply forward bias to R1 and R5, and so on.      

Therefore, by scanning across the column quickly (> 100 times per second), and turning on the respective LEDs in each row of that column, the persistence of vision comes in to play, and we perceive the display image as still.

 

Row/Col	C1	C2	C3	C4	C5
R1	0	1	1	1	0
R2	1	0	0	0	1
R3	1	0	0	0	1
R4	1	0	0	0	1
R5	1	1	1	1	1
R6	1	0	0	0	1
R7	1	0	0	0	1

Table-11

The Table-11 below gives the logic levels to be applied to R1 through R7 for each of the columns in order to display the alphabet ‘A’.

Fig.11a

By these techniques we will display the Character 'A' in the 5x7 Led Dot Matrix Display and it is look like as below;

Fig.11b

The End....

Also visit Post-10 to get idea about How Row Scanning Method is working in the LED Dot Matrix Display......

Post-10 Create A Character With Row Scanning Method In The LED Dot Matrix Display

God Bless Thx........

Create A Character With Row Scanning Method In The LED Dot Matrix Display

Basic use of Led dot Matrix Module is used to display character in different different way. For that, How to generate a character in this segment? This is simple and first question raises in our mind.

If we talking about the generating character in Module, we satisfied the law of “Persistence of Vision”. In that law, our eye is detect the static character when at a time 1/16 different frames are moving in the segments. It means that the character display on the segment it is not steady in that one but it is scanning rows or column in segments.

Way of Scanning Techniques

There are some useful techniques by which we can done software multiplexing in 5x7 Led Dot Matrix Module. These are classifying in two methods which names as follows:

                      [1] Row Scanning Method
                      [2] Column Scanning Method

[1] Row Scanning Method

Suppose we want to display the alphabet A in the common anode 5x7 led dot matrix segment. We will first select the row R1 (which means R1 is pulled high in this case), and deselect other rows by blocking their ground paths (one way of doing that is by pulling R2 through R7 pins to logic low).

Now, the first row is active, and you need to turn on the LEDs in the columns C2 through C4 of this column, which can be done by applying forward bias voltages to these columns. Next, select the row R2 (and deselect all other rows), and apply forward bias to C1 and C5, and so on.      

Therefore, by scanning across the column quickly (> 100 times per second), and turning on the respective LEDs in each row of that column, the persistence of vision comes in to play, and we perceive the display image as still.

Row/Col	C1	C2	C3	C4	C5
R1	0	1	1	1	0
R2	1	0	0	0	1
R3	1	0	0	0	1
R4	1	0	0	0	1
R5	1	1	1	1	1
R6	1	0	0	0	1
R7	1	0	0	0	1

Table.10

The Table.10 below gives the logic levels to be applied to R1 through R7 for each of the columns in order to display the alphabet ‘A’.

Fig.10a

By these techniques we will display the Character 'A' in the 5x7 Led Dot Matrix Display and it is look like as below;

 Fig.10b

The End....

Also visit Post-11 to get idea about How column Scanning Method is working in the LED Dot Matrix Display......

Post-11 Create A Character With Column Scanning Method In The LED Dot Matrix Display

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