* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download ET 238B - Diodes
Three-phase electric power wikipedia , lookup
History of electric power transmission wikipedia , lookup
Resistive opto-isolator wikipedia , lookup
Current source wikipedia , lookup
Power electronics wikipedia , lookup
Voltage regulator wikipedia , lookup
Stray voltage wikipedia , lookup
Schmitt trigger wikipedia , lookup
Power MOSFET wikipedia , lookup
History of the transistor wikipedia , lookup
Voltage optimisation wikipedia , lookup
Shockley–Queisser limit wikipedia , lookup
Surge protector wikipedia , lookup
Photomultiplier wikipedia , lookup
Switched-mode power supply wikipedia , lookup
Buck converter wikipedia , lookup
Alternating current wikipedia , lookup
Mains electricity wikipedia , lookup
Device Peripherals ET 238B Introduction Overview • Items to be covered • • • • • • Syllabus Review Lab Safety The PN Junction Diodes Transistors OP-Amps Purpose of the course • An intermediate course • Covers the design, theory and operation of electronic slot machines, casino management systems, player tracking systems, linked machines, local and wide area progressive systems. • Students will implement their design of an electronic slot machine • Who should take the course • Slot Technology students at CSN , Slot attendants in casinos and those that want to be slot Technicians that have a analog and digital electronics, employees of slot machine manufacturers, Etc. • Outcomes • Per syllabus Purpose of the course • Syllabus Review • Contact Information • Grading • Weekly Topics and Schedule Lab Safety • Precautions when working on slot machines – Appendix C handout • Remove all metal objects to reduce the possibility of electrical shock • Don’t make contact between voltages on wires and other objects – including yourself • Power should be turned off adding/removing electronic components • Helps prevent shocks and equipment damage Lab Safety • Precautions when working on slot machines – Continued • Disconnect machine before changing operating voltage/frequency settings • 110 V - 220V operation • 50 or 60Hz operation • Hopper containing coins can be very heavy • Handle all glass and sheet metal carefully • Ensure all used electrical outlets are correctly wired ET 238B - PN Junction • Atomic Structure • Characteristics • Smallest particle of an element - anything smaller is the element • Bohr Model Reference • Atomic Number • Equals the number of protons and the normal number of electrons • Determines location on Periodic Table Reference • Electron Shells and Orbits • Electrons closer to nucleus have lower energy than those further away ET 238B - PN Junction • Atomic Structure • Electron Shells and Orbits • Energy Levels • Electrons aren’t randomly dispersed • They are in different Shells (orbits) • Electrons in the same orbit have the same or nearly the same levels of energy • Reference Image • Number of electrons in each shell • Ne = 2n2, n = the shell number, (k = 1, L = 2, etc.) • Starts with Shell 1 closest to the nucleus • Valence Electrons • In outermost shell have the highest energy and are less tightly bound to the atom than closer electrons • Key to chemical and electrical properties of the element Image from: http://superstem.org/newsite/EELS.htm ET 238B - PN Junction • Atomic Structure • Electron Shells and Orbits • Ionization • The protons and electrons have equal and opposite charges • Protons are + Electrons are • When an atom absorbs energy the energy levels of electrons is raised • If the energy rise is large enough the electrons can chan levels • The necessary step is lowest for the electrons in the outer shell, the Valence Shell • If an electron gains enough energy to leave the valence shell - It is a free electron. • If an atom loses an electron I has a positive charge - if it gains an electron it has a negative charge ET 238B - PN Junction • Semiconductors, Conductors & Insulators • Conductors • Characteristics • Easily conducts electricity (also heat) • Examples of better conductors • Copper • Silver • Gold • Aluminum • Energy Gap • Small gap between Valence level and conduction level (free electrons) -- See Figure 1-5c on page 6 • See the Diagram of a copper atom Figure 1-6b on page 7 • Insulators • Characteristics • Materials that don’t usually conduct electric current ET 238B - PN Junction • Semiconductors, Conductors & Insulators • Insulators • Characteristics • Examples • Usually compounds not elements • e.g. rubber, paper, plastics • Energy Gap • Has the largest gap • Semiconductors • Characteristics • Not a good conductor or insulator • Examples • Silicon • Germanium ET 238B - PN Junction • Semiconductors, Conductors & Insulators • Semiconductors • Characteristics • Examples • carbon • compounds, e.g., gallium arsenide • Single element semiconductors all have four Valence Electrons • Energy Gap • Medium size gap between Valence level and conduction level (free electrons) -- See Figure 1-5b on page 6 • See the Diagram of a silicon atom Figure 1-6a on page 7 • Silicon vs Germanium • See Reference Diagrams of both • Reference ET 238B - PN Junction • Semiconductors, Conductors & Insulators • Silicon vs Germanium • Reference (continued) • The valence shell for silicon is closer than the one for germanium • Third shell for silicon and fourth for germanium • Germanium requires less energy to free valence electrons than silicon - thus lower threshold voltages • Silicon devices are more stable at high operating temps • Heat will cause less free electrons than in germanium devices • Covalent Bonds • Both Silicon and Germanium crystals use covalent bonding - If they are pure. • See diagram for Silicon - Reference ET 238B - PN Junction • Covalent Bonds • Characteristics • Shares a valence electron with each of the neighboring silicon atoms • Stabilizes the crystal structure • Conduction in Semiconductors • Characteristics • Semiconductors always have electrons in the conduction band (free) at a temperature of absolute zero with no other external excitation • Conduction Electrons and holes • At room temperature an intrinsic silicon crystal • Has a number of free electrons called conduction electrons • Has a number of electron holes ET 238B - PN Junction • Conduction in Semiconductors • Conduction Electrons and holes • At room temperature an intrinsic silicon crystal • Recombination is when a free electron losses energy and fills a hole • The creation of electron-hole pairs and recombination occurs randomly in an unexcited crystal • Electron and hole current • Characteristics • When an electric potential is placed across the silicon crystal • Electron and apparent hole movement isn’t random • Electron flow -Electron Current • The Positive potential of the applied voltage attracts the thermally generated free electrons • Happens in the conduction band ET 238B - PN Junction • Conduction in Semiconductors • Electron and hole current • Hole flow - Hole Current • Happens in the Valence band • Electrons in the valence band with out enough energy cannot leave the valence band • However they can move through the valence band of the crystal structure and get closer to the external - charge • N-Type & P-Type Semiconductors • Characteristics • Conductivity of silicon and germanium can be drastically increased by adding impurities • Called Doping • Used to increase either the number of holes or electrons • Two types of impurities N and P ET 238B - PN Junction • N-Type & P-Type Semiconductors • N-Type Semiconductors • N stands for the negative charge on an electron • Impurities with five valence electrons are added • e.g. arsenic (As), phosphorus (P), bismuth(Bi), antimony (Sb) • The impurity integrates into of covalent bonded crystal • The fifth electron in its valence band becomes a free electron • Electrons are the majority carriers and carry more charge • P-Type Semiconductors • P stands for the positive charge on an atom in the crystal • Impurities with three valence electrons are added • e.g., boron (B), indium (In), gallium (Ga) • The impurity integrates into of covalent bonded crystal • The lack of a fourth valence electron results in a hole • Holes are the majority carriers and carry more charge ET 238B - Diodes • Diode • Characteristics • Part of the same crystal is doped with P-Type material and part with N-Type • A junction is formed where the materials meet • There is no charge on either the N or P regions • Number of electrons equals the number of protons • Depletion Region Formation • Before the junction between the “n & p” regions is formed both regions have zero net charge • Just as the junction is formed • The n regions losses free electrons to the p region • Leaves holes and a net positive charge • The newly arrived electrons combine with p region holes • Leaves a net negative charge ET 238B - Diodes • Diode • Depletion Region Formation • The net negative and positive charged areas are free of charge carriers >>> Depletion region • The depletion region grows until the negative charge on the ptype side repels any further electrons crossing the junction • Barrier Potential • Measure of the voltage potential across the depletion region in volts • The net positive and negative charges on both sides of the junction create an electronic field • Forward Bias • Condition that allows significant current through a diode • Requirements • VBIAS > Barrier potential ET 238B - Diodes • Biasing the Diode • Forward Bias • Requirements • VBIAS + is connected to the P material and VBIAS - is connected to the N region • Process • After the electrons from the N region enter the P region they have lost energy and inter a available hole • Those electrons are then in the Valence Band • The electrons then move through the common valence band to the positive charge applied to the P region • Effectively the holes flow towards the junction • Reverse Bias • Condition that prevents significant current through a diode • Requirements • + of the reverse bias voltage is connected to the N region ET 238B - Diodes • Biasing the Diode • Reverse Bias • Requirements • - of the reverse bias voltage is connected to the P region • Initial Currents • Reverse voltage is applied then: • Electrons flow in the N region to the attached + potential • Holes flow to the attached - potential • Depletion region grows • The resulting initial rush of current quickly decreases • Reverse Current • Flows due to minority carriers in N and P regions • Holes and electrons • Carries are thermally generated electrons and at a higher energy level than the conduction band of the N region • Thus they can easily transition to the N region & fill a Hole ET 238B - Diodes • Biasing the Diode • Reverse Bias • Reverse Breakdown • Occurs when the applied reverse bias voltage is to large • Results in an avalanche current • These high currents can cause heat damage to a diode ET 238B - Diodes Copied from: http://en.wikipedia.org/wiki/Image:Rectifier_vi_curve.GIF ET 238B - Diodes • V-I Characteristics of Diodes • Forward Bias • See V-I curve on the previous slide • At any point along the curve you can take Voltage/Current values to calculate the dynamic (aka AC resistance) resistance (r’d) of the diode • Knee voltage • Nominally 0.6 to 0.7V for silicon • Nominally 0.2 to 0.3 V for germanium • red light-emitting diodes (LEDs) can be 1.4 V or more and blue LEDs can be up to 4.0 V. • Reverse Bias • See V-I curve on the previous slide • The knee voltage is the reverse breakdown voltage (VBR) • Found in Manufacture’s specifications • Above VBR the current rapidly increases ET 238B - Diodes • V-I Characteristics of Diodes • Temperature Effects on V-I Characteristics • Forward Biased • As the temperature rises the energy level of the electron in the N region rises a lower Forward Bias voltage is required • Reverse Biased • The reverse current increases, but still is very small • Diode Models • Structure and Symbol • Symbol • Conventional current follows with the implied diode arrow • Electron current flow is against the arrow • P region is known as the Anode and the Cathode is on the N region side of the pn-junction ET 238B - Diodes • Diode Models • Structure and Symbol • Electron current flow is against the arrow • P region is known as the Anode and the Cathode is on the N region side of the pn-junction ET 238B - Diodes • Major uses for Diodes • Basic DC Power Supply • Half-Wave Rectifiers • Full-Wave Rectifiers • Power Supply Filters and Regulators • Diode Limiting and Clamping Circuits • Voltage Multipliers ET 238B - Diodes • Zener Diodes • Characteristics • Major application - providing a constant reference voltage for voltage regulators • Zeners maintain near constant DC voltages under proper conditions • Designed to operate in the reverse break-breakdown region • Zener Breakdown • Two types of break down are used by Zener Diodes • avalanche breakdown • Usually have a breakdown voltage of over 5 volts • zener breakdown • Usually have a breakdown voltage of 5 or less volts ET 238B - Diodes • Zener Diodes • Zener Breakdown • Voltage Ranges • Commercially available voltages range from 1.8 to 200V • Tolerances range from 1% to 20% • Breakdown Characteristics • As VR (the reverse Voltage) increases very little current flows until the knee of the curve is reached • Knee known as the Zener Voltage • As Current increases the Zener Voltage VZ slowly increases • Remains very close to the VZ • Zener Regulation • Zener diode current must be at least = to the zener knee (IZK) current to maintain the constant voltage across it • Currents greater than the maximum rating (IZM)will damage the diode ET 238B - Transistors • Transistor Structure • Major Components • Three Doped Semiconductor Regions • Either a p-type region between two n-type regions (npn) • Or a n-type region between two p-type regions (pnp) • Separated by two pn junctions • Basic Transistor Operation • Must be biased to operate as an amplifier • Usually DC biases that are necessary for AC amplification ReverseVoltage ReverseVoltage Some images from “The Electronics Club Web site Forward Voltage Forward Voltage ET 238B - Transistors • Basic Transistor Operation • Must be biased to operate as an amplifier • Usually DC biases that are necessary for AC amplification • For both types the BE junction is forward biased • The CB junction is reverses biased • Currents • Conventional current flow is assumed. • Emitter-Base Junction • The junction has a forward voltage applied across the PN or NP junction • PNP • Positive voltage applied to the P Emitter and the negative side of the voltage to the N Base ET 238B - Transistors • Currents • Emitter-Base Junction • PNP • Positive voltage applied to the P Base and the negative side of the voltage to the N Emitter • Collector Base Junction • Major function of the junction is to remove chares from the Base • To function the junction must be reversed biased • PNP Biasing • The P Collector is connected to the negative side of the reverse voltage and the positive side is connected to the N Base. • NPN Biasing • The N Collector is connected to the positive side of the reverse voltage and the negative side is connected to the P Base. ET 238B - Transistors • Transistor action • Three factors for the Collector current to be controlled by the Base Emitter current • The emitter needs heavy doping to supply free electrons • The base only has light doping and is very thin • The collector voltage is relatively high • Usually 98% to 99% of the charges supplied by the Emitter to the Base provide the collector current • The remaining 1% to 2% provide the Base current • Electrode Currents • IEmitter = IBase + ICollector IE = IB + IC • Base current controls Collector current • This is the reason transistors can amplify signals ET 238B - Transistors • Base current controls Collector current • Walk through • Increased Forward voltage on Base Emitter junction causes more base current • More Base current means more majority carriers are in the Base region to be injected into the collector • Thus more base current yields more Collector current • Note the Collector currents are usually between 50 to 100 times the Base currents Image from Biplolar Junction Transistor Theory by Chuck McManis http://www.mcmanis.com /chuck/ ET 238B - Transistors • Typical Amplifier configurations • Common Emitter Image from Thomas L. Floyd Electronic Devices, 6e and Electronic Devices: Electron Flow Version, 4e ET 238B - Transistors • Typical Amplifier configurations • Common Collector • Used to supply larger loads with current Image from Thomas L. Floyd Electronic Devices, 6e and Electronic Devices: Electron Flow Version, 4e ET 238B - Transistors • Typical Amplifier configurations • Common Base • Characteristics • • • • Provides High Voltage Gain and no phase shift Maximum Current Gain - 1 Low Input Impedance Input applied to Emitter Circuit Image from Thomas L. Floyd Electronic Devices, 6e and Electronic Devices: Electron Flow Version, 4e ET 238B – OP-Amps • Integrated Circuit Operation Amplifiers • OP-Amps for short • OP Amp Development • Originally contained only bipolar transistors • Many OP-Amps have Junction field-effect transistors inputs • Draw extremely small currents compared to bipolar • Many have complementary MOS output transistors on outputs • Output voltages can reach within millivolts of the supply voltages • Called BiMOS • Specialized OP-Amps • High Current and/or High Voltage ET 238B – OP-Amps • Specialized OP-Amps • • • • • • Sonar send/receive modules Multiplexed amplifiers Programmable gain amplifiers Automotive instrumentation and control Radio/audio/video ICs ADCs and DACs • General Purpose OP-Amp • Circuit Symbol and Terminals • Figure to the right • • • • Reference Designator - per drawing Negative and Positive Supply Terminals Inverting input terminal - Negative terminal Non-inverting input terminal - Positive terminal LM741J ET 238B – OP-Amps • General Purpose OP-Amp • Simplified Circuitry of a 741 OP-Amp Image from a National Semiconductor data sheet. ET 238B – OP-Amps • General Purpose OP-Amp • Simplified Circuitry of a General Purpose OP-Amp • Input Stage - Differential Amplifier • The difference of the voltage across the Inverting and Noninverting Inputs Ed • Very high gain amplifier • Intermediate Stage - Level Shifter • Shifts the DC level of Input stage to match the input requirements of the Output Stage • Specifically to bias the output stage • The biasing is necessary to allow the Input stage generated voltage to the Output almost unchanged • Output Stage - Push-Pull • Most common - pnp-npn circuit • Supports a high current output ET 238B – OP-Amps • OP Amp Terminals • Ideal OP-Amp Characteristics • Has infinite Gain • Has Infinite Input Resistance • Has Zero Output Resistance • Real Power Supply Terminals • Typically Three Power Supply Terminals • V+ Connected to the OP-Amp • V- Connected to the OP-Amp • Usually symmetrical +15V up to +18 • Can be unipolar • Power Supply Common Not directly connected to the OP-Amp • Return path for current back to the Power Supply • Connected through the load to the OP-Amp • May or May-not be connected to ground • Real Output Terminals • Single -ended output • Voltage referenced to the Power Supply Common ET 238B – OP-Amps • OP Amp Terminals • Real Output Terminals • Current Limits • Usually 5 to 10 mA • Voltage Limits • Output transistors need some of the supply voltage across the transistor • Otherwise it acts as a switch - not an amplifier • With bipolar transistors - 1 to 2 volts needed • With MOS Transistors a few millivolts are required • Thus w/bipolar and +15 Supplies +Vsat = +14V and - Vsat = -13V • Circuit Protection • Usually have circuits to limit output current to 25 mA for a short • Prevents burnout • Load Resistance limits - 2k ET 238B – OP-Amps • OP Amp Terminals • Input Terminals • + and - Terminals • Differential Input Terminals • Vout depends on the difference between the input terminals times the gain of the amplifier AOL. • Ed = {V + input} - {V - input} • • • • Both are measured with respect to common Vout = Ed times AOL. Polarity matches the input - If + Input more positive then + Out If - Input more positive then - Out • Input Bias Currents and Offset Voltage • Input Bias Currents • Small currents used to activate the input transistors • Offset Voltages • Small imbalance voltages on the input terminals ET 238B – OP-Amps • Open Loop Voltage Gain • Definition Vout = Ed times AOL • Typical circuits (per Nation Semiconductor’s OP-Amp Circuit Collection Application Note 31) www.national.com/an/AN/AN-31.pdf ET 238B – OP-Amps • Typical circuits (per Nation Semiconductor’s OP-Amp Circuit Collection Application Note 31) www.national.com/an/AN/AN-31.pdf