Diodes Definition and 190 Threads

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.

View More On Wikipedia.org
Recent contents Top users
  1. Nicholas moore

    Experts in Optics: Advice needed in working with SLDs

    I'm working on a project which will involve placing a superluminescent diode in a rocket, which will get launched in desert (obviously the SLD is just part of a greater system, the objective is not the operation of an SLD) What I need to know is if you think I could make, or where I can track...
  2. STEMucator

    What Diode Has a Low Turn-On Voltage and Through-Hole Termination?

    Hi. I'm wondering if anyone knows the model number of a diode, which has a low forward turn on voltage, and has through-hole termination. I am aware of the BAT54 Schottky diode series. The turn on voltage is as low as ##0.2 V## for some models, but the problem is they are surface mount...
  3. D

    Question about pn diodes and their lifetime

    I was wondering, does the lifetime of a diode depend on how long it takes for all the free P electrons to transfer over to the p holes? In other words, do the electrons that fall into the p holes ever return to the n side?
  4. R

    Engineering Circuits w/ Diodes: Understanding Magnitude & Frequency

    http://imgur.com/9Yhwya0 So for #1, would I approach this problem by first considering the positive power applied to the top, making the diode on the right opened, and thus vouput being 4volts. Then for the next part would the diode on the left be in reverse bias, thus opened, and the voutput...
  5. R

    Can I substitute a (2) CES388 Diodes for a RB480K

    Hi All, I am trying to wire up a fairly sensitive display that calls out for 2 RB480K diodes to be connected in series as a reference (GND C A C A). I was given CES388 diodes as a substitution but since I have installed them the display has not worked. To me, I'm a mechanical engineer, the...
  6. U

    Understanding Laser Diodes: Operation & I-V Curves

    can any tell me about laser diode, how it operate and I-v curve of laser diode?
  7. S

    Do I Need Flyback Diodes for an L293D and 5V DC Motor Circuit?

    Hello, do I need flyback diodes in circuit of L293D and 5V DC motor? Thanks!
  8. I

    The Current Load: Why Do Two Diodes in Parallel Not Share It?

    why do two diodes in parallel not share the current load?
  9. A

    Electric Field in Capacitors and Diodes

    Hello, Capacitor When a capacitor is connected to a voltage source, electrons will move from one plate and accumulate in the other in accordance to Q=CV. Due to the imbalance of charges (positive and negative ions) between the plates, an electric field exists that flow in the direction of the...
  10. Domenico94

    Diodes Exercises: Engineering Student Seeks Help

    HI everyone. I'm an engineering strudent, looking for online material with exercises on diodes...anyone can send me a link here with explanations of the various exercises? Thank you very much :)
  11. Q

    Finding output of voltage for certain input voltage diodes

    Homework Statement We have the circuit in the figure.I have to find the output graphically if the input is Vi=15sinwt. Homework Equations This type of exercise doesn't have any equations The Attempt at a Solution Heres the circuit http://i.imgur.com/ivixWzH.jpg For Vi<= -10 the diode is ON...
  12. Steven Ellet

    PN-junction diode vs light emitting diodes

    Is it advisable to use an LED instead of a PN-junction diode and what is the resistance of each (or do they vary)? The only reason I'm asking is LEDs are easier and cheaper to get. P.S. What I need it for, only needs a PN-junction diode.
  13. R

    Diodes and electromagnetic emmission Help?

    How would one go about figuring out what to dope a diodes pn junction with in order to create a desired electromagnetic wavelength ?
  14. ranju

    What sets the clipping voltage in junction diode clipper circuits?

    In the given attachment there is a circuit given..and we have to find the output voltage waveform.. I have attached the options also..because according to me the " when input coltage is less than 5 V , it acts as open , most of the input voltage appears in output.. while when input voltage...
  15. JasonHathaway

    Determining two diodes' currents

    Homework Statement Assuming that D1 and D2 are ideals, determine ID1 and ID2 according to the table below. Homework Equations Circuit Analyzing methods (KVL, etc...) The Attempt at a Solution I've confirmed my solutions for the first three cases with final answers of the book...
  16. PsychonautQQ

    Anyone know lots about Tunnel Diodes? I have a poorly phrased question

    Can somebody help me understand why it is possible to have a 100% transmission rate through both potential boundaries created by a tunnel diode, while the transmission rate through only one of the walls can be very small??
  17. T

    Engineering V & I in Circuit w/ Diodes: Step-by-Step Guide

    I have to find the V and I in the following Circuit. I am not sure how to approach this problem. If someone can help me with this step by step it will be great. Assume Forward voltage drop of 0.7 volts
  18. P

    Understanding Diodes in a Circuit

    I wanted to post a similar looking circuit but I couldn't find any, so I'll have to describe it unfortunately. Imagine a circuit where you have two resistors and you want to measure the voltage across each of those resisistors so you put a voltmeter parallel to each one. Except, instead of...
  19. K

    Engineering Circuit with Diodes, Capacitors, and Resistors

    Homework Statement Compute V3(t)-V4(t). The capacitors are initially discharged, the voltage source is turned on at t = 0, and the diodes’ forward voltage drop is negligible (Vf = 0). What is the value of V3(10s) – V4(10s)? Vi=4sin(2∏t) RC= 0.1s Homework Equations i (over...
  20. T

    Question about majority and minority concentrations in diodes

    In my notes package it shows that for a REV biased diode, in the p type side, the concentration of majority carriers (pp0 holes) increases as we get closer to the junction. However, I don't get how this makes sense, since the metal contact between the negative terminal of the source and the...
  21. V

    Voltage Regulator w/ Zener Diodes

    Homework Statement The diagram: http://images.fr1ckfr4ck.fastmail.fm/probB.jpg These zener diodes; Have a test current of 5mA when 6.8V is applied (V_z=6.8V, I_z=5mA) Have an incremental resistance (r_z) of 20 ohms Knee current (I_zk) is 0.2mA Calculate the output voltage...
  22. V

    Solving the Diode Puzzle: Finding V with Diodes

    Homework Statement Hi so I have a problem that I don't exactly know how to approach, here's the diagram: http://images.fr1ckfr4ck.fastmail.fm/probA.jpg The diodes are supposed to have saturation current I_s = 10^(-15) A Homework Equations What is V? The Attempt at a Solution First I tried...
  23. V

    Effects of Load on Diode Circuit with Exponential Model

    Homework Statement The circuit in the diagram utilizes three identical diodes having I_S = 10−16 A. Find the value of the current I required to obtain an output voltage V_o = 2.4 V. If a current of 1 mA is drawn away from the output terminal by a load, what is the change in output...
  24. Q

    Engineering Diodes limiting circuit question?

    I posted this exercise given as homework in the wrong section and it got deleted.Nevertheless,I asked my teacher to solve it and so did he.Thing is I still have some unclear stuff.Please ,a crucial part of the exercise is the part b,so please pay attention to it. Homework Statement We have the...
  25. A

    Diodes & Resistance: Understanding Forward/Backward Flow

    I was learning about how diodes work , I read on some sites that diodes have a very low resistance in forward and very big resistance on backward. I read on other sites that diodes allow current in one direction only and no current in the other . So which is right , they 're not the same thing (...
  26. X

    Engineering Diode Circuit Problem: Find Current in a Given Circuit | Homework Help

    Homework Statement In the circuit below, determine the current through the diode http://img12.imageshack.us/img12/152/jar0.jpg Homework Equations V:IR 3V: Va+Vb The Attempt at a Solution This is my first time trying to solve a circuit problem involving diodes. I first tried to use...
  27. A

    How Do Diodes Behave in Different Circuit Configurations?

    Homework Statement Homework Equations The Attempt at a Solution My instructor gave us some sample problems he said might be on the exam, I tried working them out but I was having difficulty with 3 of them: For the 1st problem, when there is positive value for voltage, I got...
  28. A

    Why is P-N junction so important in semiconductor diodes?

    Hi, Iam having a hard time understanding the benefits of using a semiconductor to construct e.g. a photodiode that creates a current in proportion of the energy deposited by radiation. Text books says that semiconductor is preferred as detectors due to high density (larger chance for...
  29. G

    Circuit Problem with diodes and resistors with sine wave input

    Homework Statement Sketch Vo for the network shown (see attachment) and determine the dc voltage available. Homework Equations The Attempt at a Solution Vi is a sine like wave with amplitude of 100 V and goes on for one period. When Vi is positive, the diode on the right goes...
  30. S

    Engineering Can Kirchoff's laws and Ohm's law be used on circuits with diodes?

    Homework Statement Can Kirchhoff's voltage and current laws, and Ohm's law, be used when analysing circuits with constant voltage and current sources, but also diodes? I'm trying to analyse such a circuit, and I'm finding that current is flowing backwards through one of the diodes...
  31. S

    Engineering Circuit analysis with diodes and multiple current/voltage sources

    Homework Statement This isn't a homework question, just one I can't get the correct answer to. The circuit diagram is attached, and I need to find the voltage at V. The Attempt at a Solution Assume the voltage drop across each diode is 0.6V. Let V_5 be the voltage drop across the current...
  32. I

    Why building a BJT transistor out of two diodes is impossible?

    i had a thought to stick two diodes together such that the electronic setup was similar to that of a BJT transistor. however i have been told by multiple teachers/professors that the two were not equivalent. I have drawn a picture to show you what i mean. the top two pictures are just the...
  33. D

    Engineering How to plot output graphs of circuits involving diodes and capacitors?

    Homework Statement Given that the diodes are ideal for the circuits a) and b), plot each of their output for the input shown. Label the most positive and most negative levels. Assume CR >> THomework Equations The Attempt at a Solution I am having a really hard time understanding the role of...
  34. A

    Why Zener Diodes Don't Have Current Leakage

    Can someone help me ? i can't understand why zener diode don't have current leakage?
  35. D

    Engineering Finding Vout from circuit contain diodes.

    Homework Statement I am suppose to find an R value so that Vo=80mV given that both diodes are identical, conducting 10mA at 0.7 V and 100 mA at 0.8 V Homework Equations I = I_{s} e^{v/{V_{t}n}} The Attempt at a Solution I get that if the diodes are the same n, V_t and I_s are the...
  36. P

    Calculating Current in a Diode Circuit with Given Voltages

    http://img545.imageshack.us/img545/7113/diodeq.jpg In the circuit shown in the figure (c) above if VA=5V and VB=3V, calculate the current through RL. Please explain. Thank you
  37. D

    Can Varactor Diodes Cause Frequency Modulation in LC Oscillators?

    Okay, simple question. Why doesn't the AC voltages and currents present in an LC oscillator tank arrangement that uses a varactor diode as the C cause the frequency to be modulated at 1/2 the freq?
  38. J

    Ohmmeter & Diodes Homework: Understanding Results

    Homework Statement 2. The attempt at a solution So, I know that you can test a Diode with a ohmmeter. Based off of the R you get Very large reversed biased and fairly low forward biased. But I don't know why it would show these values. The Large one, revered biased. Kinda makes...
  39. M

    Diodes in parallel with resistors and terminal PD

    1. Homework Statement The problem is not answering the questions, as supplied by the book The book then asks you to reverse both diodes, so you still have one diode in the circuit that let's current pass through it and one that does not. When you solve for the PD at Q you use the 0.6V...
  40. J

    Can 4 Diodes in Parallel Handle a 3.6 Amp Load?

    Can one take 4 - 1 amp diodes check them with diode tester and if they match hook them in parallel and get a 3.6 amp load to pass thru them? John http://d1dtbvo20ouog7.cloudfront.net/s/help-0003.gif
  41. D

    Choosing Best Rectifier/Diodes for 12V 50A Transformer

    Hi I want to make an simple linear power supply, using an 12V 50A transformer rectifier and a capacitor. What kind of rectifier/diodes are best to avoid an excessive voltage drop from the transformer? Because using common diodes the voltage drops to 10,5V without load. Many thanks.
  42. J

    Since diodes emit light(led) and they are also used to convert ac to dc

    Are they shining brightly inside the device when used to convert ac?
  43. Z

    Diodes used for mixing - why needed?

    Diodes used for "mixing" - why needed? At the site http://www.st-andrews.ac.uk/~www_pa/...rt1/page1.html there is a very comprehensive explanation of a "mixer diode". My question: if the diode is always forward biassed to produce an output frequency of fs - fl (source minus local frequency)...
  44. O

    Reverse-Biased Diodes: Overheating, Spoilage, and Repair

    When a diode is reverse biased by a very large voltage, then it will be spoiled permanently due to overheating. Then what is happening inside the diode? Why will it spoil? Is that because the silicon atom inside the spoiled diode is changed? Can a spoiled diode be fixed? Thank you.
  45. V

    Center-tapped rectifier without diodes?

    Hi everyone. I'm back again with another silly question. Please bear with me. Below is a figure of a basic center-tapped full-wave rectifier circuit and my question is; why can't we use anything other than diodes to get a unidirectional output current? For example, what difference would it...
  46. M

    Quantum well laser diodes - Operation and design

    Quantum laser diodes. How does light escape? I recently became very interested on the functioning of these amazing devices and so I read online about the topic of quantum wells, semiconductors and lasers. After much reading I believe I can now understand the basics of lasers, resonant...
  47. M

    Clippers in Diodes: Current Flow Explained

    Observe the attached figure, and the associated graph, shouldn't be like the opposite of this graph? If it is positive the first half the current should pass the diode and it is on, no?
  48. M

    How Does Internal Resistance Affect Diode Load Line Graphs?

    Hello there, I have 2 questions: 1)What's the difference between the load line graph of a circuit having (a DC supply, diode with no internal resistance, and a resistor R) & another circuit having (a DC supply, diode WITH internal resistance, and a resistor R)? 2)If we have a circuit...
  49. D

    I want to know what do diodes facing opposite each other do?

    Dear Experts. I like to confirm that operation principle of the attached circuit. 1. what do diodes facing opposite each other do? 2. how to calculate v2 voltage? Please could you comment on this? Thanks very much.
  50. O

    Help determining where does current flow through diodes

    Hello Can anybody help me determine where does current flow in the circuit on the picture below: How it goes when Uul is >0, and how when Uul is negative (<0). There is inverting OP AMP, and Uop will be >0 when Uul is <0, right? And how it goes then through diodes? Zener diodes here...
Back
Top