Zener diode
Page 1 of 2
Light Emitting Diode :

       In  a  forward  biased  diode  free  electrons  cross  the  junction  and
      enter    into    p-layer    where    they    recombine    with    holes.    Each
      recombination radiates energy as electron falls from higher energy
      level to  a  lower energy level.  Fig39.  In  ordinary diodes this energy
      is  in  the  form  of  heat.  In  light  emitting  diode,  this  energy  is  in  the
      form  of  light.  Ordinary  diodes  are  made  of  Ge  or  Si  this  material
      block  the  passage  of  light.  LEDs  are  made  of  different  materials
      such  as  gallium,  arsenic  and  phosphorus.  LEDs  can  radiate  red,
      green, yellow, blueorange or infrared (invisible).
Typical LED current is between 10 mA to 50 mA
Seven Segment Display :

        It  contains  seven  rectangular  LEDs.  Each  LED  is  called  a  Segment.  External  resistors  are  used  to  limit  the
        currents to safe Values. It can display any letters A, B, C, D, E, F, I, H, L, P, U. Fig40.a
http://nptel.iitm.ac.in/courses/Webcourse-contents/IIT-ROORKEE/BASIC-ELECTRONIC...   5/18/2009


Zener diode
Page 2 of 2
The seven segment display are of two types common anode and common cathode. Fig.40.b

                                                                                          <> 
http://nptel.iitm.ac.in/courses/Webcourse-contents/IIT-ROORKEE/BASIC-ELECTRONIC...   5/18/2009

Posted in Posted by waytofeed at 9:42 AM