Electronics Technology Fundamentals Chapter 17 Introduction to Solid State Components: Diodes

Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved Semiconductors – P1 Semiconductors – atoms that contain four valence electrons valence

Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved. 3 It’s actually a little more complicated Atomic Orbitals by Wikipedia orbitals.com Orbitals by Chemguide Visualizing Orbitals by Hyperphysics

Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved Semiconductors – P2 Charge and Conduction Conduction Band – energy band above the valence shell Conduction Band An electron that absorbs energy and “jumps” from the valence band to the conduction band is said to be in an excited state Explaining Semiconductor Energy Bands (We’ll pretend the orbits are round otherwise the drawing is too complex)

Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved Semiconductors – P3 Covalent Bonding – the method by which some atoms complete their valence shells by “sharing” valence electrons with other atoms Covalent Bonding (Bringing atoms close to each other changes the orbital shapes into even more complex patterns)

Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved Semiconductors – P4 Conduction Electron-Hole Pair Recombination

Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved Doping – P1 Doping – the process of adding impurity atoms to intrinsic silicon to increase its conductivity Doping Trivalent: three valence electrons Pentavalent: five valence electrons Trivalent Impurity Pentavalent Impurity Aluminum (Al) Gallium (Ga) Boron (B) Indium (In) Phosphorus (P) Arsenic (As) Antimony (Sb) Bismuth (Bi)

Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved Doping – P2 N-Type Materials N-Type Materials Electrons – majority carriersmajority carriers Holes – minority carriers

Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved Doping – P3 P-Type Materials P-Type Materials Holes – majority carriers Electrons – minority carriers

Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved The PN Junction – P1The PN Junction PN Junction – n-type an p-type materials joined together

Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved The PN Junction – P2 Electron Diffusion Depletion Layer Barrier Potential

Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved Bias – P1 Bias – a potential applied to a pn junction to control the width of its depletion layer Forward Bias

Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved Bias – P2 Forward Bias (Continued) Bulk Resistance (R B ) V F ~ 0.7 V for silicon V F ~ 0.3 V for germanium

Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved Bias – P3 Reverse Bias

Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved Bias – P4 Reverse Bias (Continued)

Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved PN Junction Diodes – P1 Diode – a two-electrode (i.e., two-terminal) component that acts as a one-way conductor Diode Insert Figure 17.15

Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved PN Junction Diodes – P2 Diode (Continued)

Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved PN Junction Diodes – P3 Ideal Diode Characteristics – would act as a simple switch Ideal Diode Characteristics Reverse Biased (Open Switch) – has infinite resistance, zero reverse current, and drops the applied voltage across its terminals Forward Biased (Closed Switch) – has no resistance, and therefore, no voltage across its terminals

Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved PN Junction Diodes – P4 The Practical Diode Forward Voltage (V F ) Knee Voltage (V K ) 0.7 volts for silicon 0.3 volts for germanium Insert Figure 17.19

Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved PN Junction Diodes – P5 Practical Circuit Analysis

Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved Diode Ratings – P1Diode Ratings Peak Reverse Voltage (V RRM ) – the maximum reverse voltage that won’t force the diode to conduct Reverse Breakdown Voltage 1N Datasheet

Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved Diode Ratings – P2 Average Forward Current (I 0 ) – the maximum allowable value of dc forward current (check datasheet) Forward Power Dissipation (P D(max) ) – the maximum power dissipation when forward biased (check datasheet)

Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved Other Diode Characteristics – P1 Bulk Resistance (R B ) The natural resistance of the diode p-type and n-type materials Effects the forward operation region of the diode curve Not a simple quantity (but can be approximated by a single value)

Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved Other Diode Characteristics – P2 Bulk Resistance (R B ) (Continued) A Thevenin equivalent circuit (Good enough for most analysis)

Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved Other Diode Characteristics – P3 True Diode Curve A Thevenin approximation (good enough for most circuit analysis)

Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved Other Diode Characteristics – P4 Reverse Current (I R ) A very small amount of minority current that passes through the diode when it is reverse biased Made up of two independent currents Reverse Saturation Current (I S ) Surface-Leakage Current (I SL )

Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved Other Diode Characteristics – P5 Diode Capacitance Varactor diode or Varicap

Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved Other Diode Characteristics – P6 Temperature Effects on Diode Operation (forward bias)

Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved Other Diode Characteristics – P7 Temperature Effects on Diode Operation (reverse bias)

Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved Diode Specifications – P1 Spec Sheet Organization Maximum Ratings Table Electrical Characteristics Table 1N4001 (rectifier diode) 1N4001 1N914 (small signal diode) 1N914

Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved Diode Specifications – P2 Diode Identification K = cathode (+ for reverse bias) A = anode (+ for forward bias)

Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved Zener Diodes – P1 Zener Diode – designed to work in the reverse breakdown region of its operating curve Zener Diode Reverse Breakdown Voltage (V BR ) Application: Voltage Regulator Zener Voltage (V Z ) How to use a zener diode OnSemi

Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved Zener Diodes – P2 Zener Diode (Continued)

Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved Zener Diodes – P3 Zener Operating Characteristics Zener Knee Current (I ZK ) Maximum Zener Current (I ZM ) Zener Test Current (I ZT )

Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved Zener Diodes – P4 Zener Operating Characteristics (Continued) Insert Figure 17.35

Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved Zener Diodes – P5 Zener Operating Characteristics (Continued) Zener Impedance (Z Z ) – the zener diode’s opposition to a change in current

Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved Zener Diode Ratings – P1 Maximum Ratings dc Power Dissipation (P D ) – used to find I ZM

Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved Zener Diode Ratings – P2 Power Derating Factor – maximum power dissipation rating decreases when the operating temperature increases

Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved Zener Diode Ratings – P3 Electrical Characteristics Tolerance in electrical ratings indicated by the letter following the component number A – ±5% No number – ±10%

Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved Light-Emitting Diodes – P1 Light-emitting diodes (LEDs) – emit light when sufficiently forward biasedLEDs How Stuff Works LightEmittingDiodes.org

Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved Light-Emitting Diodes – P2 Light-emitting diodes (LEDs) (Continued) Insert Figure (Anode is positive when forward biased)

Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved Light-Emitting Diodes – P3 LED Characteristics Forward Voltage: +1.2 to +4.3 V (typical) Reverse Breakdown Voltage: -3 to –10 V (typical)

Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved Light-Emitting Diodes – P4 Current-Limiting Resistors – do not exceed the maximum current rating of the LED where V out(pk) = the peak output voltage of the driving circuit V F = the minimum rated forward voltage for the LED I F = the maximum forward current rating for the LED

Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved Light-Emitting Diodes – P5 Current-Limiting Resistors (Continued)

Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved Light-Emitting Diodes – P6 Multicolor LEDs Biasing determines color Contain two diodes that are connected in reverse parallel Typical Colors Red – one polarity Green – other polarity Yellow – if switched fast enough between the two polarities

Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved Diodes: A Comparison

Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved Diode Testing – P1 Testing PN-Junction Diodes Resistance Check

Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved Diode Testing – P2 Testing PN-Junction Diodes Diode Test

Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved Diode Testing – P3 Testing Zener Diodes In many cases, a zener diode cannot be tested like a regular pn-junction diode A zener diode can be tested by measuring the voltage across its terminals while the component is in the circuit under test

Electronics Technology Fundamentals, 3 rd ed. Paynter and Boydell © 2009 Pearson Higher Education, Upper Saddle River, NJ All Rights Reserved Diode Testing – P4 Testing LEDs Normally testing is not necessary The most common cause of LED failure is excessive current. When this occurs, a discoloration of the component occurs which is easy to recognize