What is Diode: Definition and 567 Discussions

A diode is a two-terminal electronic component that conducts current primarily in one direction (asymmetric conductance); it has low (ideally zero) resistance in one direction, and high (ideally infinite) resistance in the other. A diode vacuum tube or thermionic diode is a vacuum tube with two electrodes, a heated cathode and a plate, in which electrons can flow in only one direction, from cathode to plate. A semiconductor diode, the most commonly used type today, is a crystalline piece of semiconductor material with a p–n junction connected to two electrical terminals. Semiconductor diodes were the first semiconductor electronic devices. The discovery of asymmetric electrical conduction across the contact between a crystalline mineral and a metal was made by German physicist Ferdinand Braun in 1874. Today, most diodes are made of silicon, but other semiconducting materials such as gallium arsenide and germanium are also used.

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  1. N

    Engineering Help with a circuit problem (Zener Diode)

    Homework Statement In the circuit below, a zener diode (VON = 0.7V, VZ = -5.7 V) is in series with two resistors. Determine the current (I) if Vs is: a) 6V b) 4V c) 0.2V d) – 0.2V e) – 4V f) – 6V [PLAIN]http://img809.imageshack.us/img809/6995/zenerdiodecircuit.png Homework Equations I was...
  2. R

    Diode Malfunction: 1N4007 Troubleshooting at 900V

    Hello. I use 1N4007 diodes in a voltage multiplier near the maximum authorized 900 V (max reverse 1000 V). Some don't work and I replace them, but ... With an ohmeter they look correct and more using them with medium voltage ( 200 V ) they work perfectly. So they aren't destroyed, could someone...
  3. C

    Engineering How Do You Determine Reverse Saturation Current in Diode Circuits?

    Homework Statement Homework Equations The Attempt at a Solution Just want to know whether I have the right idea: so to determine the reverse saturation current (IS), I just determine it for each value of VD that was given? So finding IS for 0.6, 0.65, 0.7 etc? The question...
  4. K

    Designing a power supply with a center tapped-transformer and a zener diode.

    Homework Statement Design a full-wave regulated power supply using a 5:1 center-tapped transformer and a 7.5 V, 1 W Zener diode. The power supply must provide a constant 7.5 V to a load varying from 120 to 450 . The input voltage is 120 V(rms), 60HZ.Homework Equations The Attempt at a Solution...
  5. H

    Diode placement and AC waveform across load?

    Hi all. A transformer is driven with a square wave pulse. The transformer has three secondary coils all in series, a diode is placed between two of them which is forward biased during the on time. The coils are used to charge a capacitor and limit current. When the transformer is pulsed...
  6. Femme_physics

    Industrial electronics. Question with coils and diode.

    Homework Statement http://img198.imageshack.us/img198/1421/vintm.jpg Given that k = 2 A) Draw in a qualitative manner the following letters Vin, VP, Vs, Uxy, UR1, UR2, UD B) Calculate the power in R2 C) Calculate the average current through R1 The Attempt at a SolutionI'll start with a...
  7. L

    Calculating BJT Base Current with Zener Diode

    What is the BJT base current if the base is connected to a zener diode like in the circuit here - http://www.satcure-focus.com/tutor/page5.htm With a voltage divider it's thevenin's equivalent. But with zener, should I consider it as a voltage source?
  8. R

    Clippers:series circuit with diode

    hello!...I'd like to ask what are the importance of a clipper in a series circuit with diode.What is an input signal because I've read it in the book of boylestad and still i don't understand what is it.what part of the circuit that is being clip?please...it would be helpful for my report.
  9. A

    In diode why there is creation of depletion region?advanced thanks.

    in diode why there is creation of depletion region? advanced thanks.
  10. N

    Understanding the Physics of Resonant Tunneling Diodes

    Hello :) , Does anyone know some good paper or book from were it's possible to learn physics behind of work of resonant tunneling diode(RTD)? In last semester I had course in ˝microelectronics and nanoelectronics˝ and we studied basic principle on which RTD works, and it was very interesting...
  11. O

    Help: Diode doesn't behave as it should when connected to coil

    It's pretty straightforward. I built a circuit to energize a coil and connected a diode in parallel to make sure the discharge won't harm the transistor. The diode is in working order, I've tested it with a multimeter and found that it has a high resistor value when forward-biased and it doesn't...
  12. L

    Phase Shift effect on diode conduction time

    Ok, so let's say I have a simple half-wave rectifier like the one shown in the image below: http://img585.imageshack.us/img585/1904/unledmwc.jpg When it comes to the analysis of the circuit, during the positive cycle of the input voltage, the diode is forward biased and the output voltage...
  13. S

    Past exam questions: BJT and Diode

    Homework Statement [PLAIN]http://dl.dropbox.com/u/14490370/bjt.png Homework Equations beta=Ic/Ib By 'ON' I think the lecturer means the saturation region and by 'OFF' he means cut off. The Attempt at a Solution a. My reasoning is Ib= (Vs-Vbase...
  14. R

    What is the Maximum Power Dissipation for a Zener Diode Regulator?

    Homework Statement The following is a diagram of dc power supply with a Zener diode regulator. For what load current is the power dissipation of the Zener diode maximum? How would you find the approximate value of this maximum power dissipation...
  15. D

    Engineering Solving Diode Logic Circuits: 4V, B=2V, C=3V

    EDIT: I was being stupid and forgot the first diode would turn off after i worked out stuff for diode C, thanks anyway, solution found!Hi I'm having some trouble getting the correct output voltage when i model the diodes using a voltage ofset and resistors. A = 4V, B = 2V, C = 3V Using Voltage...
  16. J

    PF vs frequency in 3phase diode rectifier

    i have an assignment on PF vs frequency in 3phase diode rectifier the DR want me to draw a graph and stuff but I am not sure how 2 do it or if it does affect the PF. thank you
  17. O

    Potential barrier of Silicon Diode

    As we know the potential barrier of silicon diode is 0.7V at "Normal Temperature" But if the Temperature is 120 degree Centigrade then what will happen? 1) the Potential Barrier will increase 2) Decrease 3) Remain Same Please Explain also!
  18. F

    Creating a Voltage Transfer Characteristic (VTC) for a Zener Diode Circuit

    http://img847.imageshack.us/img847/1922/capturevq.jpg I need help starting this. So far I am getting Voh = +10V from the zener diode, and Vol = -10V, the upper and lower saturation limits based on the zener diodes Then for threshold values I am getting an upper threshold Vth = -R1/R2 * Vol =...
  19. R

    Finding the Right RF VHF Diode for GSM Signal Amplification

    Dear Experts, I am looking for some rf vhf diodes. could you recommend a particular model for me? I am quite new to this diode. Are these synonymously called microwave diode / MOSFET / rectifiers / field effect transistor? I am confused what should be the right diode to amplify gsm...
  20. L

    Understanding Clamping Diodes: Voltage Conditions and Operational Behavior

    I am trying to understand when clamping diode (at TTL gate input) works and when it does not. The voltage is -2v at cathode and 0v at anode. Fwd bias condition, but the diode does not condut, until the current is reduced. Why so? Initially I thought it was because of the fast rise/fall times...
  21. U

    Diode I-V Characteristic At High Frequency

    Hi i wonder if the diode I-V characteristics will be as usual at it is operated at high frequency? Some one told me that it will be not the same. There will be a some kind of hysteresis loop will appear in the curve. Can anyone ensure me about that or give me a useful link about that topics?
  22. PainterGuy

    Please have a look on these diode circuits

    hello everyone, i am in disagree with someone over the calculations in the circuits i will discuss with you. circuit #1: here is the diagram:- http://img156.imageshack.us/img156/2734/diodecircuit.jpg do you find it correct? please check it carefully. the circuit will only conduct...
  23. I

    Engineering Help with Diode Circuit with Current/Voltage through Diode

    Homework Statement For the circuit shown in Fig. 4.26 both diodes are identical. Find the value of R for which V=80mV Homework Equations I'm not quite sure what equation to use here. If you look at the wiki page on diodes http://en.wikipedia.org/wiki/Diode it might be Shockleys...
  24. T

    How Does a Magnetic Field Affect a P-N Diode?

    Homework Statement What happens when a P-N Diode is placed in a magnetic field? The Magnet is 1 Tesla and the voltage is 0.7 volts. Homework Equations The Attempt at a Solution On the internet I found that there is a Hall effect when a semiconductor is placed in a magnetic field...
  25. S

    Pn - junction diode experiment - varying heat

    Homework Statement This isn't exactly a problem, but I need help with an experiment. I've got to design an experiment to show a) the variation of voltage with a diode when the diode is in forward bias b) The variation of current (i think) with heat, keeping voltage constant. The thing is...
  26. B

    Electronics help recitifier with a zener diode

    Homework Statement Design a rectifier with a zener diode that satisfies the following: Primary voltage = 120V @ 60Hz VDC = 12V IR2 = 100 mA (R2 being the load) Vr(R2) <= .3V Homework Equations C=IDC/(2fVr) IDC=IR3 + IR1 The Attempt at a Solution I tried calculating the...
  27. P

    Ideal Diode: Exploring Negative Voltage Drop and Its Feasibility

    I am a little unsure about why the ideal diode can't have positive voltage drop... Looking back at my notes, it just simply says that "It's not a feasible solution" and that only when voltage drop is zero or negative can there be a solution.
  28. PainterGuy

    There will be current when diode is reverse biased

    hi everyone, please see fig 42.25 a and b on this google doc:--- https://docs.google.com/viewer?a=v&pid=explorer&chrome=true&srcid=0B_XrsbDdR9NEMDNhNzVhZTktNzZhMy00ZGI0LWEyZGYtM2RmMTA3MDQxMTlm&hl=en&authkey=CKP-7OsD i can understand the fig 42.25a and why the current flows. but i have...
  29. D

    What is the Function of a Diode in Protecting an NPN Transistor?

    Homework Statement The absolute max voltage rating for the base-emitter voltage is the lowest of all values. This low value means the B-E junction must be protected from a high reverse voltage. A diode is used for an npn transistor. Explain its function and conditions under which...
  30. F

    Forward biased diode operation

    Hello Forum, trivial questions: physics phenomena are usually explained via simple models. In DC electronics the water analogy is often adopted but breaks down when we move to AC. When a simple diode is forward biased DC current is able to flow in the circuit powered by a constant voltage...
  31. J

    Calculating η for a Diode: A Puzzling Experiment

    Homework Statement I have been doing an experiment, and I needed to calculate the value of η for a diode. The value should be between 0.5 and 1.0... The value for alpha obtained is 20. Homework Equations αV=ηeV/kT Where k is Boltzmann’s constant, eV is the electron volt, T is...
  32. K

    Understanding Current & Voltage in Circuits A & B w/ Diode and Battery

    So I'm trying to understand the relationship between current & voltage as well as the basic electricity laws and Diode operation. Attached are 2 circuit diagrams for reference. Assume that Diodes can withstand against whatever voltage/current the circuit generates. Can Anyone explain me what...
  33. D

    How Does Modifying the Load Resistor Affect a Zener Diode Circuit?

    Homework Statement What would happen if the load resistor was short-circuited. What would happen if the load resister was removed? -see attached diagram- Homework Equations P=Iin^2*R Pz=IzVz =(Iin-Iout)Vz=[((Vin-Vz)/R)-Iout]Vz The Attempt at a Solution I'm not sure about...
  34. Q

    Exploring P-N Diode Voltage Drops

    Homework Statement ok i was doing an experiment on p-n diodes i was asked to plot graph of voltage across resistor VS voltage of diode with a DC source varying from 0 to 30V resistor 1k ohm The Attempt at a Solution i understand the forward bias where the graph shows that the voltage across...
  35. F

    Fastest modulation: laser diode vs LED

    fastest modulation: laser diode vs LED... Hello Forum, in the telecomm industry, the most common and economical form of modulation is direct modulation, acting on the current operating LEDs or diode lasers. Using an external intensity modulator (OOK), like a super fast chopper, the...
  36. H

    Level shifting with a reverse biased small signal diode

    I have found a circuit that uses a BAS16 small signal diode to level shift a 5V (or 3.3V) TTL signal down to a 1.8V TTL signal. The cathode of the diode is on the high voltage side and the anode is on the low voltage side, so it looks like it is backwards compared to the direction of current...
  37. S

    Band diagram of pn-junction diode at low temperature

    Hi What could be the band diagram of pn-junction diode at very low temperature where dopant ionzation is completely frozen out? Would it still be like the band diagram at room temperature?
  38. H

    Diode in a series LC circuit and voltage at resonance?

    A series LC circuit at resonance has a higher total voltage than the applied voltage due to voltage magnification. If a diode were inserted between L and C it would prevent the back and forth oscillation of energy, But would it prevent voltage magnification if the circuit were driven at...
  39. E

    Two Diode AND Gate - New to EE

    Hi, I am new to EE. On this page - http://hyperphysics.phy-astr.gsu.edu/hbase/electronic/diodgate.html#c1" - the very first circuit shows a diode-resistor AND gate. How does that work? I understand the OR gate shown right below it, but... the two inputs on this AND gate are connected to reversed...
  40. E

    How Is Resistance Calculated in Different Bias Regions of a Diode?

    Note: This is a past paper, I'm simply revising for an exam. But I thought that this was the best forum to stick it in. Homework Statement http://exampapers.cf.ac.uk/papers/engin/en1051/en1051a09.pdf Section A, Q1 c http://img684.imageshack.us/img684/9695/questionm.jpg Homework Equations...
  41. E

    How Do You Calculate Diode Parameters from Characteristic Points?

    Hi Please help me to solve the following problem: Homework Statement There are three points given on diode characteristic (1N4148 diode) Q1=(50uA, 0.6V) Q2=(500uA, 0.7V) Q3=(2mA, 0.75V) I have to calculate: Is - reverse bias saturation current n - emission coefficient...
  42. T

    Finding a TVS Diode for 137mV Back EMF Protection

    Hey, I'm trying to find a suitable diode to protect against some back EMF in my circuit, but I don't know much about them and so I'm having a really hard time finding one. If someone could look at what i need and then possibly send me a link i'd be so grateful. Requirements: back EMF = 137mV...
  43. D

    What is the function of D1 in this circuit?

    The attached circuit is not my design but I need to understand it completely. This is a circuit that supplies power to a sensor. When S1 is closed the power is removed from RL. What is the purpose of D1? In General, what happens if R1 were to short? I know the base would be subjected to the...
  44. M

    IV Characteristics of Simple Diode Circuits

    I'm trying to figure out what the IV characteristic curves are of some simple diode circuits. A) Diode and resistor in series. B) Diode and resistor in parallel C) Diode and resistor in parallel, and this combo in series with another diode reversed wrt. first diode. Its been a while...
  45. A

    Zener Diode connected in serie

    Hi. A circuit has two zener diodes connected in series. The voltage reaches the diode's reverse breakdown voltage (VzDiode1 and VZDiode2 are the same = 10V). The Vi of the all circuit is 8 V. / / 8v -----|<|----|<|---- Ground / / +...
  46. S

    Help with diode model in multisim

    I am trying to build a simple laser diode driver problem is, I built the circuit without taking the diode into consideration, and am getting the right current outputs (45mA for 0 bit and 90mA for a 1 bit) but every time I insert an LED just to kind of simulate the laser diode, I get some...
  47. M

    Pulsed laser diode driver - how it works?

    Hi everyone, I've been looking at the data sheet for a pulsed laser diode driver that I've been using, and I've managed to convince myself that there's a mistake. I was hoping that if I post my explanation of how the circuit shown in the data sheet works, that you guys can either confirm that...
  48. L

    Simple Diode Problem: Solving for Unknown Voltages using KCL and KVL

    Homework Statement [PLAIN]http://img27.imageshack.us/img27/4475/q12r.png Homework Equations KCL/KVL Mesh current, node voltage ohm's law The Attempt at a Solution for b) I understand how diodes work, and i'v deduced that diode 2 is definitely not conducting as the voltage on it's anode is...
  49. K

    What Happens to Voltage in Parallel Diodes Connected to an AC Source?

    two ideal diodes are are connected in parallel. this combination is connected across an ac source. the diodes r such that if one of them is forward biased other is reverse biased. now in the positive half cycle let us take that 1st diode if forward biased and the second reverse biased. if the...
  50. S

    Diode and retifier application?

    diode and retifier application?? i have a question are diode and rectifiers used in electrical transformers?
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