PN junction

• Trivalent - 3 valence electron atom

  • Boron
  • Gallium
  • Indium
• Tetravalent - 4 valence electron atom

  • Germanium
  • Silicon
• Pentavalent - 5 valence electron atom

  • Antimony
  • Arsenic
  • Phosphorus
• Two types of extrinsic materials

  • N-type
  • P-type
• Introducing impurity elements that have 5 valence electrons

  N-type materials
• Introducing impurity elements that have 3 valence electrons

  P-type material
• In 1904, John Ambrose Fleming invented the 


  Vacuum tube
• a vacuum tube contained how many electrodes?

  2
• in 1906, Lee Dee Forest added a 3rd electrode called control grid and the 


  triode
• triode was used as an amplifier and a switch
• application of triode created a new era with the invention of

  the crystal radio sensor
• Diode consists of the barrier potential, the small forward dynamic resistance and the large internal reverse resistance

  Complete diode model
• adds the barrier potential to the ideal switch model

  practical diode model
• is a simple switch. When the diode is forward biased, it can act like a closed (on) switch. When the diode is reversed biased, it act like an open (off) switch

  Ideal Diode model
• Focused single colour light source in the compact disc player

  laser diode
• Light sensor in remote control circuit

  Photo diode
• variable capacitor in a tune circuit

  varactor diode
• oscillator circuit in an oscilloscope

  tunnel diode
• Indicator light in electronic circuit

  LED
• Voltage regulator in power supply circuit or voltage clipper in power supply circuit


  zener diode
• Signal sensor in diode

  Signal diode
• Rectifying power supply circuit

  Power diode
• rectifier = penerus
• It is the maximum allowable voltage in the reverse bias region, at which diode resistance changed abruptly from very high impedance to very low impedance

  Break down voltage
• It is a very small current due to drift current in the diode in the reverse bias region. 


  Saturation current
• Saturation current is very low due to 


  High impedance of the depletion region.
• It is also called the knee region


  threshold voltage
• the part of the reverse region where the diode impedance is very low, and the current passing through the diode is very high


  break down voltage
• It is the operation region at which the potential applied to anode is more positive than that applied to the cathode


  forward region
• it is the operation region at which anode potential is more negative than cathode potential


  Reverse region
• The polarity of applied voltage which causes charge to flow through the diode is called

  forward bias
• the polarity of applied voltage which cant produce any current is called

  reverse bias
• the joint between the p type and n type material is called

  PN junction