What is Diodes: Definition and 190 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. 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

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    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

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  6. U

    Understanding Laser Diodes: Operation & I-V Curves

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  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

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  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

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  12. Steven Ellet

    PN-junction diode vs light emitting diodes

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  13. R

    Diodes and electromagnetic emmission Help?

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  14. ranju

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  15. JasonHathaway

    Determining two diodes' currents

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  16. PsychonautQQ

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

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  17. T

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

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  18. P

    Understanding Diodes in a Circuit

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  19. K

    Engineering Circuit with Diodes, Capacitors, and Resistors

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  20. T

    Question about majority and minority concentrations in diodes

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  21. V

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  22. V

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  23. V

    Effects of Load on Diode Circuit with Exponential Model

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  24. Q

    Engineering Diodes limiting circuit question?

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  25. A

    Diodes & Resistance: Understanding Forward/Backward Flow

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  26. X

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

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  27. A

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  28. A

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  29. G

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  30. S

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

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  31. S

    Engineering Circuit analysis with diodes and multiple current/voltage sources

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  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

    Diodes, supplies, and 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?

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  50. O

    Help determining where does current flow through diodes

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