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Electrical presentation on pn diodes.


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pn diodes and its types explained nicely.

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Electrical presentation on pn diodes.

  1. 1. PN DIODES Atif Imam NIIT UNIVERSITY B.Tech(1st Year) CSE
  2. 2. SEMICONDUCTOR DIODE Theory of p-n junction . p-n junction as diode. Ideal diode. Volt-Current characteristics. Diode biasing Different types of Diodes.
  3. 3. Theory of p-n junction When a p-type semiconductor material is suitably joined to n-type semiconductor the contact surface is called a p-n junction. P N ++ Depletion region
  4. 4. p-n junction as diode  Also called as semiconductor diode .  The left side material is a p-type semiconductor having negative acceptor ions and positevely charged holes. The right side material is n-type semiconductor having positive donor ions and free electrons . Cathode Anode Symbol P Construction N
  5. 5.  When forward biased, a diode acts as a conductor and current flows  When reverse biased, a diode acts as an insulator and no current flows. Forward Biased Reverse Biased
  6. 6. IDEAL DIODE When the diode is ON, it acts like a short circuit and current flow When the diode is OFF, current is zero, so it acts like an open circuit
  8. 8. Diode Biasing Forward Biased Short circuit D D I R V R V Reverse Biased Open circuit D D I=0 V R V R
  9. 9. Types of Diodes • • • • • • • • Light Emitting Diode (LED) Avalanche Diode. Laser Diode. Schottky Diode. Zener Diode. Photo Diode. Varicap Diode or Varactor Diode. Rectifier Diode.
  10. 10. ZENER DIODE  It was named after Clarence Zener, who discovered this electrical property.  It Permits current in the forward direction as well as in the reverse direction if the voltage is larger than the breakdown voltage or “Zener knee voltage” or “Zener voltage”.  USES  Zener Diode Shunt Regulator.  Zener Diode as Peak Clipper.  Switching operation.
  11. 11. USES OF ZENER DIODE 1. Zener Diode Shunt Regulator 2. Meter Protection 3. Zener Diode as Peak Clipper 4. Switching operation.
  12. 12. Light-emitting diodes (LEDs)  Emits visible light when an electric current passes through it.  LED’s are essentially pn diodes operated in forward bias. Benefits Of LED: • Low power requirement. • High efficiency. • Long life. Applications: • • • • Indicator lights. LCD panel backlighting. Fiber optic data transmission. Remote control.
  13. 13. Photo Diode  A type of photo detector capable of converting light into either current or voltage.  Designed to operate in reverse bias. Incident light Front Contact Absorbtion in the depletion layer causes current to flow across the photodiode and if the diode is reverse biased considerable current flow will be induced Insulation p+ Active Area Depletion region n- region n+ Back Diffusion Back Metalization Rear Contact USES : Used in: • CD Players. • Smoke Detectors. • Light sensors • Various medical applications, such as detectors for computer tomography and pulse oximeters.
  14. 14. Tunnel Diode (Esaki Diode)  It was introduced by Leo Esaki in 1958.  Heavily-doped p-n junction  Impurity concentration is 1 part in 10^3 as compared to 1 part in 10^8 in p-n junction diode  Width of the depletion layer is very small (about 100 A).  It is generally made up of Ge and GaAs.
  15. 15. Thank You !