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. E

    Why Does Current Rise Exponentially in a Diode After Reaching +0.6V?

    so I've seen this graph all over the internet, but nowhere seems to explain why the current after +0.6v rises exponentially and not just straight up. is it mainly due to the internal resistance of the diode or is there significant inductance/capacitance in there as well. what's the dominating...
  2. D

    Which Diodes do I need for this application?

    I am adding a function to the rear Turn Signals on my motorcycle (12vDC negative ground system). Turn Signals have 1157 incandescent bulbs - they have two filaments and three wires: ground, hot to running light, and hot to flasher. I want my Turn Signals to ALSO act as Brake Lights. So all...
  3. U

    Questions about diodes, relativity, radiations

    Hi, Given below are some questions which I have attempted and all I want to know now is whether they are correct or wrong and what the correct approach should be. So please check all my answers and point out the mistakes. Thanks. 1. Why do ordinary silicon diodes not emit light? A. Because...
  4. S

    Polyphase rectifier: Calculating the diodes needed.

    Hello, I have created a theoretical coil of 170 turns*.4871 Tesla's*.0045m^2/.06 seconds=6.21V (Faraday of course.) ohm's of the coil=.405 6.21V/.405ohms=15.33A The equation I used -N * curl*B*A/curl*t N=number of turns; B=Tesla's; A=area of the coil; t=Time; curls cancel out. (To...
  5. U

    Need help regarding flywheel diodes

    Hi all. This is my first post here. Really hope someone can help :) Im facing some problem regarding the design of my little switch mode boost regulator. It uses the max631, which has a built it catch diode. The input voltage to the max631 comes from a logic controlled p channel mosfet...
  6. A

    Turn-on voltage of pn junction diodes

    Hey, I am working on a report and got stuck at two discussion questions. Help & discussion would be greatly appreciated! 1. What factors determine the turn-on voltage of a pn junction diode? Explain its dependence on the factors you mentioned My guess would be that the light intensity on...
  7. M

    Calculating voltage drop across diodes

    Hey guys I am completely new to this site and electronics so forgive me. I've uploaded a photo of the question. I am trying to work out at what values does just D1 conduct D1 and D2 conduct then finally all of them. Im really stuck here. i know that the diodes start conducting when the...
  8. R

    Diodes at super low temperatures

    Yesterday, my Chemistry professor talked about super low temperatures and semiconductors becoming superconductors. So I was wondering, would a LED still light up as a superconductor?
  9. D

    Circuit analysis with diodes

    How do I do basic circuit analysis of circuits that have diodes in them? For example, if I have a basic circuit consisting of just a voltage source, a resistor, and a silicon diode, how would I calculate the current in the circuit?
  10. C

    Using Diodes with AC Induction Generator: Tips & Troubleshooting

    I have built an AC induction generator. The only diode I have I took off of an old computer, but I used my multimeter's diode test, so I'm pretty sure that it still works fine. I want to be able to connect a DC ammeter (with needle, not digital) to the generator (if I connect it just plainly to...
  11. S

    References for Pulsed Laser Diodes Research

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  12. L

    Schottky diodes and the Shockley-Haynes experiment

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  13. D

    Comparing Zener and Rectifier Diodes

    Heya. I might be completely overlooking something here, but is a zener diode pretty much a normal rectifier diode used backwards? For a rectifier diode to conduct, the voltage across it must be greater than some forward voltage value, but the idea behind the zener diode seems to be exactly the...
  14. I

    How does the presence of a diode affect the average power in a circuit?

    [SOLVED] Average power and diodes. Hi, I have this question. If a diode were connected to a circuit with an alternating current and there was a resistor was connected to it, will the average power change? For example, if we take the following values, V max = 6.0 V Resistance = 100 ohms...
  15. N

    Electronics (Diodes + capacitors) questions

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  16. O

    AC to DC conversion voltage regulators and zener diodes question

    I am at the last stage of AC-DC conversion. I understood filtering all right. but when the filtered signal arrives at the regulator, isn't the regulator supposed to change that 'ripple' signal into a straight line?? Also, is there a derivation for the diode IV equation somewhere?
  17. DaTario

    How do diodes (pn junction) work?

    Hi all, I would like to know how pn junction work? thanks DaTario
  18. T

    Do diodes need to be put in, in a certain direction?

    I was given a christmas present and i have now begun making it and I've run into a problem,:confused: does the colour code on diodes relate to where and what direction that they need to be soldered into? please respond
  19. M

    How Do Diodes Function in Various Electronic Applications?

    From what I've gathered a diode is used to make the current flow in one direction but block the flow in the other direction. Does that mean diodes are only used in AC circuits since a DC circuit only flows one way anyway?
  20. S

    Need advice on diodes connected in series

    can someone advice me on how the graph should look like for a circuit with diodes connected in series? Can we model the diodes this way? Attached picture shows the graphed charecteristic for 1 diode. If its for 3 diodes, how should the graph look like? Am i right to say that Vt will...
  21. S

    Circuit w/ Diodes: Voltages & Conducting?

    I'm suppose to calculate the voltages across the diodes.. but I was wondering in this situation, are both diodes conducting, or is only the first one conducting because there is more power in that, and it shuts off the other one.
  22. I

    Can Diodes Become Nonlinear and Cause Device Failure at Reverse Breakdown?

    Why are diodes nonlinear?
  23. M

    Dumb question about circuits with diodes

    I'm at a loss as to how there is an output voltage for this circuit when I think the diode is facing in the wrong direction. Or is it possible to get an output voltage? Can someone help me analyze it. Just assume resistance is R and current through resistor is I and voltage drop across diode...
  24. R

    My LED: Connecting Diodes for Voltage Drop

    Hi, this is my diode: http://img201.imageshack.us/img201/2862/untitledmq1.png Ok, I know Vcathode < Vanode in order for the LED to light up through the current sent through it. Now, my question is, if the three Diodes are connected to 0v, Vanode > Vcathode, therefore the LED will light...
  25. S

    Circuit Troubleshooting: Finding Correct States of Diodes

    Today in class we learned about diodes. Our prof explained to us that the only manual way to find the correct states of the diodes is guess and check. Each time, we ended with one correct circuit; that is Kirchoff's laws coincided with the diode constraints. Now I'm doing this circuit on my...
  26. E

    Engineering Design a Circuit Using Diodes, Resistors and Voltage Sources

    Hello, I have this problem: design a circuit using diodes, resistors and voltage sources to obtain the input function. And the input function is Iin vs Vin plot with following points connected as straight lines: (2V,0mA), (3V,2mA), (4V,6mA). I guess I need a hint on what kind of topology...
  27. E

    How Do Diodes Work? An Explanation

    I do not know much about diodes and I wanted to know if someone could explain me how do semi conductor diodes work and how do we determine in a circuit(dc and ac) the input voltage and the output voltage...
  28. X

    Buck Converters: Why NFETs and not Diodes

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  29. N

    Diodes and EE - Grasping the Basics

    Usually I can pick up most concepts pretty quickly, but EE just makes me feel dumb. Ive managed to grasp most concepts we have covered this semester, except one, diodes. I really don't understand how to determine forward or reverse bias. For example...
  30. T

    Solving Current-Voltage Characteristic of P-N Diodes with ln i = ln i˚ + eV/2kT

    For the current-voltage characteristic of a p-n diode which is foward biased: ln i = ln i˚ + eV/2kT where i˚ = a constant current e = electronic charge k = Boltzmann constant T = absolute electron temperature i and v are current and voltage respectively, for which I have a series of...
  31. N

    Can I use inexpensive laser diodes to create white reflecting hologram ?

    I read the tutorial on http://www.3dimagery.com/ on how to create a white light reflecting hologram but the He-Ne laser is too expensive for me . So I want to ask that can I use inexpensive laser diodes in the place of He-Ne gas lasers . Besides that I see the websites say that the...
  32. R

    Favorite laser-pointer color? (hurray for diodes)

    I'm giving a small talk soon, so I've decided I should probably have a pointer to keep things on track. However, there are too many colors available, it's overwhelming; I don't like making decisions. My thoughts: Red just isn't that cool anymore. The dot is small and not very visible by...
  33. S

    Semiconductor light-emitting diodes

    Hello, i have a revision question that I'm only part-able to answer. The question is: Explain why an LED operating at a fixed current would be more stable than one operating at a fixed voltage.Consider the effect of the device heating on the IV characteristics.Explain under which condition...
  34. C

    Semiconductor P-N Junctions: Transistors or Diodes?

    Is a semiconductor with a p-n junction considered a transistor or just a diode? If it is just a diode, are transistors always triodes?
  35. E

    Why Do Some FETs Have Base Diodes?

    I was curious if anyone knew why some FETs have base diodes. The only purpose I can imagine is wanting current to flow in a direction when the FET is off because when the diode is on current flows through the channel bypassing the diode and when the FET is off there is no current flow at all so...
  36. D

    Can Aluminum Actually Steal Electrons from Silicon in a Diode?

    I have a question regarding diodes. Aluminum has 3 valence electrons, and normally bonds with 3 atoms in order to rid itself of the valence electrons, right? Okay, but when mixed in a matrix of silicon atoms, it doesn't have enough electrons to share with the silicon. This makes a hole...
  37. Y

    Bringing Some Humor to Laser Diodes: Fun Jokes

    Does anyone know any laser jokes? I'm doing a short presentation on laser diodes and thought it might be fun to include a refreshing page of jokes near the end. I found a few on Google, but none were very funny.
  38. J

    Understanding Operation of Back-to-Back Schottky Diodes

    I have been searching for a description of how these diodes operate. I am reasonably familiar with solid state physics and the physics of semiconductors and think I have worked out how these should work (being two back-to-back Schottky diodes) based on the Fermi levels and band-bending, but I'm...
  39. K

    Blue Diodes: Finding the Right Manufacturer

    Are there any Manufacturers of Blue Diodes ?
  40. ShawnD

    Peltier Effect and Diodes: How Does it Work Both Ways?

    The Peltier Effect is when the temperature of a P-N semiconductor interface increases or decreases in temperature due to the current flowing through the interface. The temperature change due to the Peltier Effect is dependant on which way the electrons are flowing. What I want to know is how...
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