Components the diode


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Components the diode

  1. 1. The Rectifier DiodeThe diode will pass electric current in one direction only.It is used in power supplies as a rectifier to convert AC voltages toDC voltages.The diode is the simplest form of semiconductor device used inelectronics and is formed using a single P-N junction.conventional current flowCathode -Anode +NPelectron flow
  2. 2. Simple Rectifier CircuitThe simplest rectifier circuit is called the ‘Half-Wave’ rectifier as itonly converts one half cycle.Since current passes in one direction only, the negative portion ofthe waveform is blocked.0 t+-VoViI D-acmainssupply+ViVodc(unsmoothed)voltageVF
  3. 3. Rectifier Diode CharacteristicsThe rectifier diode has a low resistance in the forward direction and a very highresistance in the reverse direction. It therefore passes current in one directiononly.A diode which is reverse-biased will not pass a significant current, however ifthe reverse voltage rating is exceeded the diode will break down. This voltage iscalled the maximum reverse voltage (VRRM ).VFIF(mA)-IR(µA)ForwardbiasVR0.4 0.6ReversebiasbreakdownVoltage(VRRM )silicongermanium
  4. 4. The Rectifier Diode – CharacteristicsActivitySilicon Diode (1N4001)Select your components and instruments place them on the breadboard.Connect the components to form the circuit shown using link wire.Set power supply voltage to 15 voltsAdjust current from 0 to 20mA in 2mA steps and record your resultsGermanium diode (OA91)Repeat the above for the germanium diode.R1470ΩDC POWERSUPPLY15VVR11kΩVFMulti-meter set tovolts(2V)++IFObjective: To measure and compare the characteristics of a silicon andgermanium rectifier diode.R1470Ω+-TESTDIODEMulti-meter set tocurrent(100mA)
  5. 5. The Rectifier Diode – Characteristics ActivityBreadboard layout and ConnectionsSelect your components and instruments place them on the breadboardas shown and connect the test instruments.AmmeterIF-+VoltmeterVF+ -DC PowerSupply+15vR1470ΩVR11kΩ- TESTDIODE
  6. 6. The Zener DiodeThe Zener diode is a silicon junction diode designed to operate in thereverse conduction mode and provide a stable voltage across its terminals.It is used to provide a reference voltage in comparator circuits, powersupply circuits and constant current sources.It can also be used to provide a regulated supply to a load but haslimitations where the load can change.conventional current flowCathode +Anode -
  7. 7. Zener Diode ApplicationsThe zener diode provides a stable voltage (VZ) from a varying source voltage (VI).Circuit analysisILOADIZR+-+-VZITVIVRIT = IZ + IL amps ohmsR =VI - VZITVR = VI - VZ voltsR+-+-Regulated (Fixed)output voltage,(VO )Unregulatedinput voltage(VI )Typical application
  8. 8. Zener Diode CharacteristicsThe zener diode will pass electric current in both directions, however it isusually operated in the reverse bias mode.Its resistance is high in the ‘reverse’ direction until the zener breakdown voltage(VZ ) is reached. At this point the diode conducts as its resistance becomes verylow, maintaining a constant voltage across its terminals.VFIF(mA)-IR(mA)ForwardbiasVR 0.6VReversebiasZener breakdownVoltage(VZ )Breakdowncurrent(IZ )
  9. 9. Diode Types and MarkingsDiode types range from small signal glass and general purpose ceramic to highcurrent stud mounted.Applications include power supply rectifiers, protection and detector circuitsfor radio tuning.Diodes are identified using an alphanumeric code and the cathode is identifiedby a bar.Package styles range from miniature glass bead to large metal stud. Studmounted styles print the diode symbol orientated to identify the polarity.1 watt rectifierdiode30 watt rectifierdiodeGermaniumsignal diode
  10. 10. The PN JunctionA p-n junction is a piece of semiconductor material in which part of the material is p-typeand part n-type.At the junction donated electrons called majority carriers diffuse into the p-type materialand the acceptor holes diffuse into the n-type materialThe area in the region of the junction becomes depleted of holes and electrons due tore-combination and is called the depletion layer.Impurity atoms(fixed)p - type material n - type materialHoles(mobile carriers)Electrons(mobile carriers)Electrons(negative charge carriers)Holes(positive charge carriers)Depletion layer