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Electrical presentation on pn diodes.
 

Electrical presentation on pn diodes.

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pn diodes and its types explained nicely.

pn diodes and its types explained nicely.

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  • When diode is FB and applied voltage increase from zero, hardly any current flos through the device in beginning. As soon as VB is reach, current through the diode increase with increase of battery voltage.When the diode is RB, majority carriers are blocked and a small current flow through diode. As the reverse voltage is increase from zero, the reverse current quickly reach saturation value, Io or leakage current. When reverse voltage exceeds a certain value called zener voltage Vz, leakage current increase sharply and the curve indicating zero resistance at this point.
  • Forward biased:When voltage is applied across a diode in such a way that the diode allows current, the diode is said to be forward-biasedReverse Biased:------When voltage is applied across a diode in such a way that the diode prohibits current, the diode is said to be reverse-biased
  • Light Emitting Diode (LED): It is one of the most popular type of diodes and when this diode permits the transfer of electric current between the electrodes, light is produced. In most of the diodes, the light (infrared) cannot be seen as they are at frequencies that do not permit visibility. When the diode is switched on or forward biased, the electrons recombine with the holes and release energy in the form of light (electroluminescence). The color of light depends on the energy gap of the semiconductor.Avalanche Diode: This type of diode operates in the reverse bias, and used avalanche effect for its operation. The avalanche breakdown takes place across the entire PN junction, when the voltage drop is constant and is independent of current. Generally, the avalanche diode is used for photo-detection, wherein high levels of sensitivity can be obtained by the avalanche process.Laser Diode: This type of diode is different from the LED type, as it produces coherent light. These diodes find their application in DVD and CD drives, laser pointers, etc. Laser diodes are more expensive than LEDs. However, they are cheaper than other forms of laser generators. Moreover, these laser diodes have limited life.Schottky Diodes: These diodes feature lower forward voltage drop as compared to the ordinary silicon PN junction diodes. The voltage drop may be somewhere between 0.15 and 0.4 volts at low currents, as compared to the 0.6 volts for a silicon diode. In order to achieve this performance, these diodes are constructed differently from normal diodes, with metal to semiconductor contact. Schottky diodes are used in RF applications, rectifier applications and clamping diodes.Zener diode: This type of diode provides a stable reference voltage, thus is a very useful type and is used in vast quantities. The diode runs in reverse bias, and breaks down on the arrival of a certain voltage. A stable voltage is produced, if the current through the resistor is limited. In power supplies, these diodes are widely used to provide a reference voltage.Photodiode: Photodiodes are used to detect light and feature wide, transparent junctions. Generally, these diodes operate in reverse bias, wherein even small amounts of current flow, resulting from the light, can be detected with ease. Photodiodes can also be used to generate electricity, used as solar cells and even in photometry.Varicap Diode or Varactor Diode: This type of diode feature a reverse bias placed upon it, which varies the width of the depletion layer as per the voltage placed across the diode. This diode acts as a capacitor and capacitor plates are formed by the extent of conduction regions and the depletion region as the insulating dielectric. By altering the bias on the diode, the width of the depletion region changes, thereby varying the capacitance.
  • Uses:1.Zener Diode Shunt Regulator or voltage regulator.. It may provide a constant voltage from a Source whose voltage may vary appreciably. A current limiting resistor Rs is connected serial to Zener diode, it is necessary in the circuit to limit the current in safe value.The voltage source Vs and resistor Rs is so selected such that the Zener diode operates in breakdown region. The diode voltage in this region, which is also the voltage across the load Rl is called Zener voltage, Vz and the diode current is called Zener current, Iz.The series resistor Rs absorbs the output voltage fluctuations so as to maintain voltage across the load constant. Zener diode is reverse connected to the input voltage whose variations are to be regulated.->Meter ProtectionZener diode may also find its applications in meter protection. The Figure shows how a Zener diode protect meters from excess voltage that is applied accidently.In this case Zener diode is connected parallel to meter. In case of accidental overload, most of the current will pass through the Zener diode and so the meter movement will be saved from damage.->Zener Diode as Peak ClipperZener diodes can be used to clip off the peak value of input wave form.Figure shows the circuit diagram for Zener as peak Clipper.For positive input half cycle diode D1 is Forward biased and acts like a short while diode D2 acts like an open uptoVz.Therefore diode D2 goes into breakdown and holds the output voltage constant at Vz till input voltage falls below Vz in the latter part of positive half cycle.->SWITCHING OPERATIONZener diode can produce a sudden change from Low current to High current, so it is useful for switching applications. It is quite fast in switching operations.- See more at: http://www.mycircuits9.com/2012/07/zener-diode-applications.html#sthash.7d6JGJqW.dpuf
  • Uses:1.Zener Diode Shunt Regulator or voltage regulator.. It may provide a constant voltage from a Source whose voltage may vary appreciably. A current limiting resistor Rs is connected serial to Zener diode, it is necessary in the circuit to limit the current in safe value.The voltage source Vs and resistor Rs is so selected such that the Zener diode operates in breakdown region. The diode voltage in this region, which is also the voltage across the load Rl is called Zener voltage, Vz and the diode current is called Zener current, Iz.The series resistor Rs absorbs the output voltage fluctuations so as to maintain voltage across the load constant. Zener diode is reverse connected to the input voltage whose variations are to be regulated.->Meter ProtectionZener diode may also find its applications in meter protection. The Figure shows how a Zener diode protect meters from excess voltage that is applied accidently.In this case Zener diode is connected parallel to meter. In case of accidental overload, most of the current will pass through the Zener diode and so the meter movement will be saved from damage.->Zener Diode as Peak ClipperZener diodes can be used to clip off the peak value of input wave form.Figure shows the circuit diagram for Zener as peak Clipper.For positive input half cycle diode D1 is Forward biased and acts like a short while diode D2 acts like an open uptoVz.Therefore diode D2 goes into breakdown and holds the output voltage constant at Vz till input voltage falls below Vz in the latter part of positive half cycle.->SWITCHING OPERATIONZener diode can produce a sudden change from Low current to High current, so it is useful for switching applications. It is quite fast in switching operations.
  • BENEFITS:Low power requirement: Most types can be operated with battery power supplies.High efficiency: Most of the power supplied to an LED or IRED is converted into radiation in the desired form, with minimal heat production.Long life: When properly installed, an LED or IRED can function for decades.APPLICATIONSIndicator lights: These can be two-state (i.e., on/off), bar-graph, or alphabetic-numeric readouts.LCD panel backlighting: Specialized white LEDs are used in flat-panel computer displays.Fiber optic data transmission: Ease of modulation allows wide communicationsbandwidth with minimal noise, resulting in high speed and accuracy.Remote control: Most home-entertainment "remotes" use LEDs to transmit data to the main unit.

Electrical presentation on pn diodes. Electrical presentation on pn diodes. Presentation Transcript

  • PN DIODES Atif Imam NIIT UNIVERSITY B.Tech(1st Year) CSE
  • SEMICONDUCTOR DIODE Theory of p-n junction . p-n junction as diode. Ideal diode. Volt-Current characteristics. Diode biasing Different types of Diodes.
  • 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
  • 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
  •  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
  • 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
  • V/I CHARACTERISTICS
  • 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
  • Types of Diodes • • • • • • • • Light Emitting Diode (LED) Avalanche Diode. Laser Diode. Schottky Diode. Zener Diode. Photo Diode. Varicap Diode or Varactor Diode. Rectifier Diode.
  • 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.
  • USES OF ZENER DIODE 1. Zener Diode Shunt Regulator 2. Meter Protection 3. Zener Diode as Peak Clipper 4. Switching operation.
  • 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.
  • 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.
  • 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.
  • Thank You !