Basic semiconductor physics, diodes, the nonlinear diode model, load line analysis, large signal diode models, offset diode model, transistors, large signal bjt model, load line analysis, small signal model and transistor amplification. Contd notes and anderson2 sections part 2 preface and sections 5. Making the usual assumptions calculate the peak current in the main switch. Introduction to semiconductors, doping, generationrecombination, te carrier concentrations. Basic electronics notes on vi characteristics of zener. Rectifier diodes are a vital component in power supplies where they are. A diodes iv characteristic is shown in figure 6 below.
Although it was ine of the first types of diode ever made, the schottky diode is widely sued because it is able to provide a very low forward voltage drop. Since the reverse saturation current, is is typically very small 109 to 1015 a, the expression. As a result the schottky barrier diode is used in a varity of applications from rf design to power. Use the diode equation for that state to solve the circuit equations and find i d and v d 3. Due to this properties a diode can be used for several applications like rectifiers, sampling circuits, demodulators, logic gates and so on. Use the diode equation for that state to solve the circuit equations and find i.
The schottky diode or schottky barrier diode is used in a variety of circuits. Diodes and diode circuits tlt8016 basic analog circuits 20052006 5 assumed states for analysis of ideal diode circuits example 3. This causes a excess drift current, and can be amplified to act as. Aug 31, 2008 lecture series on electronics for analog signal processing i by prof. Zener diode operates in reverse bias rb at the zener voltage v z. Zener diodes with glass or black resin encapsulation. Although there are many different types of diode which use the same basic structure of an area of ptype material meeting an area of ntype material, the different types are optimised to provide different characteristics which can be used in a variety of ways in many. Piv is the peakinversevoltage of the diode forward bias occurs when the ptype block is connected to the positive terminal of the battery and the ntype is connected to the negative terminal of the battery, as shown below. Peak inverse voltage peak inverse voltage piv across the diode. It acts as a diode, which can serve in electronics as a rectifier, logic gate, voltage regulator zener diode. To overcome this problem we make one terminal of the transistor common to both input and output terminals. A zener diode is a type of diode that permits current to flow in the forward direction. Lecture notes microelectronic devices and circuits.
The type of diode also has some importance in defining the forward voltage drop. The relationship is obtained by applying kvl and it is vs vg r im. A zener diode is a special diode that is optimized for operation in the breakdown region. They are both devices that allow current to flow only in one direction. A check valve presents a small resistance if the pressure p 0, but blocks the ow i. Note to those familiar with a diode turn on voltage. At first glance, this looks like an insulator but the actual behavior is far more interesting, if we apply external voltages properly n n p collector emitter base moderately doped lightly doped, and very thin heavily doped. Every diode has a maximum reverse voltage breakdown voltage that cannot be exceeded without diode damage. The rectifier described above is used as the freewheel diode in a step down switching dcdc converter which is delivering 10a at 12v from a 48v supply. Appnotes and technical articles and documentations offer analysis, design ideas, reference designs, and recommendations to better implement diodes incorporateds products. Zener diodes diodes that can be made to conduct backwards. Zener diode is a reversebiased heavilydoped pn junction diode which operates in the breakdown region. The semiconductor diode is a widely used electronics component found in many electronic circuit designs today. Separating out the dc or bias analysis and the signal analysis is a technique we will use extensively d d d s r r r.
Diodes and diode circuits tlt8016 basic analog circuits 20052006 8 half wave rectifier with smoothing capacitor figure 3. A zener diode is a type of diode that permits current to flow in the forward direction like a normal diode, but also in the reverse direction if the voltage is larger than the breakdown voltage known as zener knee voltage or zener voltage. Special types of diodes called zener diodes are designed to operate in the zener breakdown region. Diodes and transistors pdf 28p this note covers the following topics. Determine the polarity of the voltage across the diode, then replace the diode with. Diodes in the first lecture, we discussed linear circuit components resistors, capacitors, and inductors we found that we could build some electronic circuits using only these devices however, much of electronics in particular. The pn junction is a versatile element, which can be used as a. By using an led and a zener diode we can create a circuit which gives turns on the led when a voltage exceeds a certain value. Poissons equation, work function, ms energy band diagrams lecture 9. This effect, called zener breakdown, occurs at a precisely defined voltage, allowing the diode to be used as a precision voltage reference. Yellow and green indicator leds, an infra red photodiode. Smith detector zsimilarly to a solar cell, light hits a pn diode, and electrons and holes are generated. Radhakrishna rao, department of electrical engineering,iit madras. Excess populations and minimum carrier lifetime, photoconductivity.
A pn junction is the metallurgical boundary between the n and pregions of a semiconductor crystal. Diodes and transistors university of california, berkeley. A zener diode is a pn junction semiconductor device designed to operate in the reverse breakdown region. Would you recommend that this diode be used in a circuit which switches at 200khz. Typically, a silicon diode will have a vf around 0. Zero current flows in a reversebiased ideal diode i.
A point contact diode with glass encapsulation and a schottky diode. Diodes in the first lecture, we discussed linear circuit components resistors, capacitors, and inductors we found that we could build some electronic circuits using only these devices however, much of electronics in particular digital electronics depends upon nonlinear devices. As nouns, the terms diode and rectifier are almost interchangeable. The ideal diode characteristic equation is known as the shockley equation, or simply the diode equation. Figure 5 depicts the real diode iv characteristic for a fairly typical silicon diode for positive diode voltages. Zero voltage drop occurs across a forwardbiased ideal diode i.
When the diode is negative biased, no current can flow in the r, so vout 0. Zener diodes are designed to operate in the reverse breakdown region. The active portion of a zener diode is a semiconductor pn junction. Although there are many different types of diode which use the same basic structure of an area of ptype material meeting an area of ntype material, the different types are optimised to provide different characteristics which can be used in a variety of ways in many electronic. What is the difference between the diode and the rectifier. A diode may be thought of as an electrical counterpart of a directional valve \check valve. Zener diode is on when it operates on the zener region, i. Zener diode made specially to operate in the reverse breakdown region. Such junctions show a pronounced rectifying behavior.
Diode circuits and applications technology innovation and. Recipe for solving diode circuits state of diode is unknown before solving the circuit 1. They are also called pn diodes in analogy with vacuum diodes. Iv characteristics, practical ohmic contacts, smallsignal capacitance pn junction diodes lecture 10. Transistors now that we know about diodes, lets put two of them together, as follows.
For the zener diode we are using a model with a breakdown voltage vz and an. This reverse breakdown called zener breakdown occurs very sharply. Diode behavior forward bias exponential behavior reverse bias breakdown controlled breakdown. Diodes and diode circuits tlt8016 basic analog circuits 20052006 11 3. A specific diode s vf depends on what semiconductor material its made out of. Base, emitter and collector but when we connected it in a circuit, we require four terminals. Currentvoltage characteristic of a zener diode with a breakdown voltage of 17 volt. Zener diodes the simplest of all voltage regulators is the zener diode voltage regulator. For more protection consider the following clipping circuit.
A simple zener diode voltage regulator in the voltage regulator the zener diode operates in the breakdown region, which ensures approximately constant voltage across it. Technical information, application notes and articles. Ee lecture notes university of california, berkeley. Zener diode characteristics in the forward region, the zener diode acts like a regular silicon diode, with a 0. Diode theory diode as a conductor when a voltage is applied current will flow. Basics currentvoltage characteristic of a zener diode with a breakdown voltage of 17 volt. Lecture 24 mosfet basics understanding with no math. Lecture 24 mosfet basics understanding with no math reading. Basic diode electronics introduction to diodes the pn junction the pn junction is a homojunction between a ptype and an ntype semiconductor. Includes details of pn junction operation which is not covered in this course.
Lecture 1 introduction to semiconductors and semiconductor. Alan doolittle lecture 24 mosfet basics understanding with no math reading. The breakdown voltage of a zener diode is carefully set by controlling the doping level during manufacture. The main characteristic of a pnjunction or a diode is that for positive voltages forward bias the diode is conduction, whereas for negative voltages reverse bias the current flow is blocked. Hbd854 zener theory and design considerations handbook. Write down all circuit equations and simplify as much as possible 2.
Lightemitting diodes leds in a diode formed from a direct bandgap semiconductor, such as gallium. Wei es154 lecture 8 18 perform the small signal analysis of the diode circuit biased with v dd by eliminating the dc sources and replacing the diode with a small signal resistance the resulting voltage divider gives. The iv characteristics of a zener diode and the corresponding constantvoltage model are shown below. Zener diode definition, vi characteristics, and breakdown. This is the voltage required to reach a flat band diagram and sets an upper limit typically an overestimate for the voltage that can be applied to a diode before it burns itself up. Pn junctions consist of two semiconductor regions of opposite type. Light emitting diode led graz university of technology. This causes a excess drift current, and can be amplified to act as a receiver for optical signals from an optical fiber. The large amount of current that will then flow could destroy the diode. Many types of diode are used for a wide range of applications. The transductance curve of a jfet is a graph of output current i d vs input voltage v gs as shown in fig. Electronic devices chapter 3 special purpose diodes the zener diode a major application for zener diodes is as a type of voltage regulator for providing stable.
The reverse breakdown of a pn junction may occur either due to zener effect or avalanche effect. This causes the holes to move toward the depletion region and the free electrons to move toward the depletion region. Alan doolittle intel develops worlds smallest, fastest cmos transistor santa clara, calif. Biasing the field effect transistor transductance curves.
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