Diode theory diode as a conductor when a voltage is applied current will flow. Smith detector zsimilarly to a solar cell, light hits a pn diode, and electrons and holes are generated. Electronics 1 lecture 9 free download as powerpoint presentation. Lecture 16 the pn junction diode ii mit opencourseware. The circuit above shows an example of diodeimplemented or gate. Write down all circuit equations and simplify as much as possible 2. Making the usual assumptions calculate the peak current in the main switch. Transistors now that we know about diodes, lets put two of them together, as follows.
For more protection consider the following clipping circuit. Special diodes varactor diodes diodes and diode circuits. Large signal switching of diode 32 as long as the stored charge is positive forwardbias diode voltage across diode is smallfew 10 mv kt 1 ev n n n a p p p e sd storage time ie pw n p n w n. The characteristic curve for the tunnel diode is made up from several different elements normal diode current. 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. Special diodes zener diodes diodes and diode circuits. When v in is greater than zero, the diode shorts, so v out 0. Ee105 fall 2014 microelectronic devices and circuits. Some of the more common specialpurpose diodes are i zener diode ii lightemitting diode led iii photo diode iv tunnel diode v varactor diode and vi shockley diode.
Biasing the field effect transistor transductance curves. Zero current flows in a reversebiased ideal diode i. Note to those familiar with a diode turn on voltage. A zener diode exhibits almost the same properties, except the device is specially designed to have a reduced breakdown voltage. Radhakrishna rao, department of electrical engineering,iit madras. Every diode has a maximum reverse voltage breakdown voltage that cannot be exceeded without diode damage. Ch3 diode circuits 12 inputoutput characteristics when v in is less than zero, the diode opens, so v out v in. Lecture series on electronics for analog signal processing i by prof.
The pn junction excited by a constantcurrent source i in the reverse direc tion. The diode is said to be forward biased when the anode is more positive than the cathode. Junction capacitance is present in all reverse biased diodes because of the depletion region. A diode can be used as a temperature measuring device, since the forward voltage drop across the diode depends on temperature.
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. Light emitting diode led graz university of technology. Part 5 large signal complete model and small signal limited use models of a diode reading. The transductance curve of a jfet is a graph of output current i d vs input voltage v gs as shown in fig. All the diodes that weve been looking at up till this point, if we operate them in reverse voltage they either look like an open circuit or, if you put too much.
Pn junction diode and characteristics of pn junction diode. Natarajan, department of physics, iit madras for more courses visit. Ee lecture handouts pdf format download adobe acrobat to read pdf files. It acts as a diode, which can serve in electronics as a rectifier, logic gate, voltage regulator zener diode. This causes a excess drift current, and can be amplified to act as a receiver for optical signals from an optical fiber. 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. 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. A pn junction diode is a twoterminal electronics element, which can be classified as either step graded or linear graded. The depletion region shrinks allowing current to flow. Peak inverse voltage peak inverse voltage piv across the diode. 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. Pn junction diode 7 diode equation where i s reverse saturation current a v d voltage applied to diode v q electronic charge 1.
Figure 5 depicts the real diode iv characteristic for a fairly typical silicon diode for positive diode voltages. The ideal diode characteristic equation is known as the shockley equation, or simply the diode equation. Pn junction diode is one of the fundamental elements in electronics. Diodes and diode circuits tlt8016 basic analog circuits 20052006 8 half wave rectifier with smoothing capacitor figure 3.
How is the bandgap related to the photon frequency. Alan doolittle 2 2 ln ln ln i a d bi a i d p n bi n n n q kt v n n n q kt n x n x q kt v movement of electrons and holes when forming the junction for nand1015cm3 in silicon at room temperature, vbi0. The ideal diode will have zero resistance when forward biased, however real diodes require that the forward bias exceed a threshold voltage v f before forward conduction begins. From the shockley ideal diode equation given above, it appears the voltage has a positive temperature coefficient at a constant currentbut depends on doping concentration and operating temperature. Recipe for solving diode circuits state of diode is unknown before solving the circuit 1. Diodes and diode circuits tlt8016 basic analog circuits 20052006 5 assumed states for analysis of ideal diode circuits example 3. Aug 31, 2008 lecture series on electronics for analog signal processing i by prof. The pn junction and the diode effect, current in the diode, the pn diode as a circuit element, circuit applications of ordinary diodes, power supplies, power supply filtering, split power supply, diode gate, diode protection. Would you recommend that this diode be used in a circuit which switches at 200khz. Copy rights 2002 highspeed information transmission lab. Page 1 1 lecture 21, slide 1 eecs40, fall 2003 prof.
P type and n type semiconductors, takenseparately are of very limited use. A diode is a twoterminal electronic component that conducts current primarily in one direction. Texas instruments transistor and diode databook 1st ed 1973 datasheets for diodes from 1n251 on and transistors from 2n117 on acrobat 7 pdf 34. And you may recall that when we looked at a diode we have the n. Fast recovery epitaxial diodes fred characteristics applications examples. Since the reverse saturation current, is is typically very small 109 to 1015 a, the expression. When the diode is in forward conduction, the voltage drop across the diode is. Also the zener diode or voltage reference diode topology is designed in a way that the diode exhibits a controlled breakdown and allows the current to keep the voltage across the zener diode close to the breakdown voltage. Tlv431 description features typical application circuit pin. A diodes iv characteristic is shown in figure 6 below. King varactor diode voltagecontrolled capacitor used in oscillators and detectors e.
Zero voltage drop occurs across a forwardbiased ideal diode i. Determine the polarity of the voltage across the diode, then replace the diode with. This is the current that arises as a result of the tunnelling effect. Basic diode electronics introduction to diodes the pn junction the pn junction is a homojunction between a ptype and an ntype semiconductor. The problem with matrix circuits is that, when several notes are pressed at once, the current can flow backwards through the circuit and. Due to this properties a diode can be used for several applications like rectifiers, sampling circuits, demodulators, logic gates and so on. If we join a piece of p type material to a pieceof n type material such that the crystalstructure remains continuous at the boundary. And were looking, now, at a device called a varactor diode. 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. Circuit symbol for the device is also shown with the \inward arrow depicting the ptype material side. Mack adjunct associate professor lecture 7 the junction diode chris mack, 20 1.
Pn junction diode 2 diode introduction a diode is formed by joining an ntype semiconductor with a ptype semiconductor. A zener diode is much like a standard diode in many respects, except that it is designed to operate in and notice here the reverse breakdown region of its operating curve. When the diode is negative biased, no current can flow in the r, so vout 0. Use the diode equation for that state to solve the circuit equations and find i d and v d 3. This is the normal or expected current that would flow through a pn junction diode. Pn junction diode 1 ee105 fall 2014 microelectronic devices and circuits prof. Connect inductorfreewheeling diode here, minimizing track length at this pin to reduce emi. The tlv431 can be used as a replacement for zener diodes in many applications requiring. Diode circuits tutorial pdf 25p this note covers the following topics. I d i sevdvt 1 as described in the last slide, i d is the current through the diode, i s is the saturation current and v d is the applied biasing voltage. Solid state devices lecture 15 pn diode characteristics. 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.