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. P

    Why bulbs and LED diodes keep glowing after being switched off?

    The bulb/LED is connected to a long cable consisting of two insulated wires. I want to know how is this phenomenon happening in a physical way. I mean, not referring to the quality of used materials. I suppose that for the bulb, it happens kinda Joule effect, and when the circuit becomes...
  2. OwlsInATrenchcoat

    B What Is the Physical Significance of Logarithmic IV Graphs in Diodes?

    Hello there, I've been working through a task (that doesn't have an answer sheet or explanation) in which we plot I against V for three different diodes. Each has a different threshold voltage and displays the usual charcteristic curve. The final question is this: "It is suggested that the...
  3. A

    Effect of doping concentration on the depletion width of p-n junction diodes

    My question for now is as follows: Why does a high doping concentration causes a decrease in the thickness of depletion region. Any help will be highly appreciated! Thanks a bunch Regards!
  4. J

    Understanding the second approximation of diodes

    My understanding of barrier potential is as follows : Due to the holes and electrons combining in the diode a depletion region is formed. Essentially this region has no mobile charge carriers (as the holes and electrons have combined) and thus the ions (whose holes/ electrons have combined)...
  5. S

    The electric field of a piecewise uniform 1D charge distribution

    This is not really homework, but I'm having trouble understanding it intuitively. I came across this when learning about the space charge layer of a diode. The solution I know simply uses the 1D form of Gauss's law: ##\vec{\nabla} \cdot \vec{E}## = ##\dfrac{\rho}{\epsilon_0}## becomes...
  6. S

    A Effect of the driving current on the divergence values of laser diodes

    Dear readers, What happens to the divergence values of a laser diode (along and perpendicular to the emitting surface) when the driving current is increased or the output power is increased? Does the divergence: Increase along one axis? Increase along both axes? Decrease along both axes...
  7. shushi

    Novice question about Relays, Capacitors, and Diodes

    Hello, In regards to this relay, TQ2SA-1.5V Panasonic 2 Form C AS Single side stable, 1.5VDC 2A DPDT NON-LATCHING SMD Relay https://www.mouser.com/ProductDetail/769-TQ2SA-1.5V PDF 1 of Relay PDF 2 of Relay (specifically pages 5-6) is attached at the bottom as a pdf file. I was previously told...
  8. P

    With two DC charging sources, are blocking diodes required?

    I have a simple 12vdc system on a boat with a single battery bank. There is a stock alternator on the engine and I've inherited a solar panel i'd like to install. I understand that most solar charge controllers have built in back feeding prevention, but will i also need blocking diodes on the...
  9. L

    Exploring the Effects of an Insulator Between Two Diodes

    What would happen if we put two diodes together with an insulator in between? p/n/insulator/p/n
  10. C

    Is Ohmic Resistance Applicable to Diodes?

    Well I was just wondering how ohmic resistance works in a diode . I mean let's take forward bias mode.In forward bias mode electrons are diffused from the n type region to the p type region.The depletion layer still exists but is very narrow.So according to Drude model of ohmic resistance...
  11. Kizteku

    Can't handle finding currents on the diodes

    Hello All, 1. Homework Statement I am confused about applying constant voltage drop model or iteration model . While trying to find the diode currents, results obtained from iteration is not consistent ( I_d1 and I_1k is not equal) so the diode currents . ALsoIs this convenient to use...
  12. Nik_2213

    Crafting Tunnel / Esaki Diodes: What Facilities Are Needed?

    This is not a home-work or course-work question. It is hypothetical, driven by curiosity. Are any Tunnel / Esaki diodes being made ? What grade of eg University facility / silicon forge would be required to craft a bespoke batch ? Yes, I know a few Russian 'New Old Stock' diodes some-times...
  13. Wrichik Basu

    Why are there three wires in secondary coil of transformer?

    This is a 12-0-12 transformer that I intend to use in my circuit: Why are there three wires in the secondary? One is of course the neutral (in black). Why are there two live wires? As an additional question, can I use four 1N5408 rectifier diodes to convert the output of this transformer to...
  14. J

    Using 6 Diodes for a 30 Amp Battery Charger

    I was told once that two 1 amp tv type diodes parallel will not work because one will always carry the load, but I am working on a car 30 amp battery charger and it has 6 diodes 1/2" press in type all parallel same as from a 10DN series Delco alternator from the 60's where they used three...
  15. avner yakov

    What the difference between pin and pn diodes i-v curve?

    For my understanding there should be no big difference in i-v curve between regular p-n junction and p-i-n junction, the only difference i can think about is do to the bigger resistance of the intrinsic layer. The curve should look the same only the current will rise little bit slower, because...
  16. E

    Comparing Resistance in PN Diodes

    Homework Statement I came across a question asking " which one of these circuits has the largest resistance to the current? Homework EquationsThe Attempt at a Solution * In A the positive terminal of the battery is connected to the p-type region and the negative one to the n-type region...
  17. J

    Two parallel diodes in a circuit

    Homework Statement Homework EquationsThe Attempt at a Solution I am not quite sure how to deal with the two diodes in parallel . How do we know what is the potential applied across the two diodes so as to decide which one is conducting ?
  18. J

    Output voltage in circuit with diodes

    Homework Statement Homework EquationsThe Attempt at a Solution Since both D1 and D2 are forward biased for the positive half cycle for the voltage input , current will flow through them . Both the diodes offer very little resistance , but do they act like connecting wires when forward biased...
  19. S

    LC circuits in series with Diodes

    I need help understanding what will happen when the switch in closed in this circuit. What I want to happen is for Cap B to charge first and then discharge into Cap C. When the charged capacitor begins to discharge, will it charge Caps B and C at the same time? It will have to overcome the...
  20. A

    Bridge Rectifiers: How Do They Work?

    Ok so I've been reading a book on electronics and I got to a section that talks about full-wave bridge rectifiers. This is the diagram the author gives: In this diagram he says the D2 and D4 diode are forward biased. But, doesn't the current flow through D2, goes through the resistor, and then...
  21. A

    Understanding the Cockcroft Walton Generator: How Does it Work?

    Hi everyone. I am doing some research about Cockcroft Walton Accelerators, because I need to be able to explain them to others as a part of a project. However, in order to understand the Cockcroft Walton Accelerator, I need to be able to understand the Cockcroft Walton Generator first. I have...
  22. D

    How do you calculate the power requirement for a circuit? (laser diodes)

    I have 52 laser diodes, rated 5VDC, 5mW, wired in parallel and powered by a battery, rated 5V, 2A (I measure 2.7). I'm thinking some diodes burn out because as the voltage drops, the current becomes too great. The diodes manufacturer states the maximum operating current of each diode is 20mA. I...
  23. K

    B A couple of questions about diodes and the depletion region

    In a diode, we have N side, P side, and a depletion region, made of positive and negative charged sides. N side and P side of the diodes are neutral charge. In N side there are free electrons. In the positive charged side of the depletion region, there are positively ionized atoms that "lack"...
  24. Ravenous Travis

    How strict is the voltage rating on laser diodes?

    Hey everyone, this is semi-related to electrical engineering and a quick search didn't appear to turn anything up regarding this question specifically so I figured this is an appropriate place to ask this. I've bought this laser diode rated for 1.9 - 2.2 volts for a project I'm working on. I've...
  25. Majorana

    TRAPATT diodes -- looking for sources of parts

    Hello everybody, I wish to do some experiments with TRAPATT (TRApped Plasma Avalanche Triggered Transit) diodes, but after much googling I was unable to find the name of any manufacturer of such diodes. Anybody with useful pieces of info?... Thank you! :bow:
  26. maverick_starstrider

    I Transport in PV Cells (and pn diodes)

    Hi, I'm having some trouble wrapping my head around some of the concepts and language of charge transport in Photovoltaic cells (and thus pn-diodes). My biggest problem is understanding the role played by the emitter region vs. the depletion region. In a typical PV cell the front emitter...
  27. K

    What is the purpose of these diodes in a PLC circuit and why are they necessary?

    Hello not sure if I've posted this in the right section. But could someone tell me the purpose of the zener diode and the diode in parallel with the resistor? Never seen this configuration before. Thanks!
  28. M

    Electronic Circuit with 2 diodes

    Homework Statement I have to find Vo in every diode state possible. We know diode Vf = 0.7 Homework Equations Va-Vc < 0.7 = diode OFF Va-VC > 0.7 = diode ON The Attempt at a Solution State 1: if D1 OFF and D2 OFF Vo will be equal to Vi State 2: if D1 OFF and D2 ON Vo will be equal to...
  29. Alkozy

    How Can I Understand the Solution for Diodes Homework in Electronics?

    Homework Statement A picture of the problem is provided in the attachment Homework Equations there is no special relations except I= Is x e^(vd/Vt) The Attempt at a Solution i have a solution for from the solution manual but i do not understand it like the I2 equation i don't get reasonable...
  30. D

    H-Bridge - diodes (or rather the lack of)

    G'day all! I've got an H-bridge here from an old motorised toy.. as I want to use it for something else and the RF receiver is no use to me for this project i figured i' strip the H and stripboard it. I noticed though that there are no diodes to protect the four transistors (yes they are...
  31. Bassa

    How Do You Calculate Current in a Diode-Resistor Series Circuit?

    Helo, I am in an electronic course and we just started studying diodes. I am stuck on the following problem: Place a 100 ohm resistance in series with a diode, and plot current versus voltage across the series combination. I am also given the following values for the diode: n = 1, Is =...
  32. DakotaE

    Trying to determine the size of Diodes required

    Hey All, i just joined today to try and figure out what size of diodes i need for the project I am working on. I am working on installing a new Light Bar and Flood Lamps to my Jeep to get better light at night. This is my hope to accomplish: Relay 1 will be used to turn the LED Light Bar and...
  33. whatphysics

    Calculating Q points for diodes

    Homework Statement In Figure Q22, the empirical junction diode equation is : (eqn is in the picture attached) for both diodes D1 and D2, where VT = 26 mV at room temperature, n = 1, IS = 3.5 x 10-14 A, R1 = 600 Ω, R2 = 300 Ω, R3 = 200 Ω, VS = 9 V. Calculate the Q-points ID = _____ mA and VD =...
  34. Cocoleia

    Why is it not possible for D2 to be off in this diode problem?

    Homework Statement I am working on this problem, where I need to find I and V Homework EquationsThe Attempt at a Solution I know the right answer will be when D1(left) is off and D2(right) is on, we went over the solution in class. I wanted to do the 4 assumptions just to try to understand. I...
  35. Cocoleia

    Diodes & Rectifiers: Homework Solutions

    Homework Statement I am practicing problems like this: where Vs=10V, R=2kohm, they say it is like a battery + ideal diode with VD=0.7V I have to sketch the transfer characteristic Vo=f(Vs) and draw the waveform of Vo(t) Homework EquationsThe Attempt at a Solution I am really unsure how to go...
  36. M

    I Voltage Relationships in Diodes: Exploring Bandgap, Temp & Flux

    Hello, does anybody know if there is a connection between the voltage (work) for the bandgap of a diode, the temperature voltage and the flux voltage?
  37. R

    Engineering Get Current and Voltage with a Circuit with Diodes

    Homework Statement Find the V and I in the circuit shown below: Homework Equations D1 or 2 is off=short circuit D1 or 2 is on=open circuit The Attempt at a Solution So, my confusion lies with deciding the on and offs of D1 and D2 . My assumption is that both of them are on and that is due...
  38. moenste

    Find current and PD across a circuit with diodes

    Homework Statement When answering the questions below, you may assume that the source resistance is negligible and that each diode has a potential difference of 0.6 V across it when conducting. For the circuit below calculate (a) the current in the 30 Ω resistor, (b) the current in the 60 Ω...
  39. S

    Protection on Step up and Step Down Converter Module Bucks

    In a circuit that I'm building, I have a power source of 5 volts DC that powers various components. A few of them are LED lights and light bulbs. -Background Info- In circuit 1, I have a step up buck "2A DC-DC boost step-up Conversion module MicroUSB 2-24V 3V to 5v-28V 12v 9v 24v"...
  40. G

    How Does Voltage Affect Diode Current Flow?

    I want to make something clear. Most diodes have in their datasheet some current for a given treshold voltage. For example a led will pass 20mA current when 4volts are applied to it. Or a zener diode's minimum turn on current is 10mA when 5,6 volts are applied across it. Does this mean this...
  41. B

    Finding voltage change for current change for diode

    Homework Statement Find the change in diode voltage if the current changes from 0.1 mA to 10 mA. Ans. 120 mVHomework Equations V2-V1=VTln(I1/I2)The Attempt at a Solution That is all the information given. The only equation I can think to use is the diode voltage/current relationship, but a...
  42. A

    Why does the voltage drop across a diode change with increasing current?

    Homework Statement I have recently performed an experiment where the voltage drop and current through a diode were measured. I am wondering why the voltage drop across the diode changes. Theoretically, the voltage drop should stay the same as there is a certain amount of energy required to get...
  43. JasonHathaway

    Diode Current & Output Voltage Calculation with V(1)=10 V and V(0)=5 V

    Homework Statement If V(1)=10 V and V(0)=5 V, and the voltage threshold for all diodes is 0.6 V. Determine the current through every diode and the output voltage Vo if V1=V4= 5V and V2=V3=10 V. Homework Equations Basic KCL & KVL. The Attempt at a Solution I know that the basic idea to...
  44. Hassan Raafat

    Voltage Multiplier: Why Don't Current Divide Between Diodes?

    in Voltage Tripler and Quadrupler , why don't current divide between two diodes ( D1 , D3 ) or ( D2 , D4 ) ? they are forward in the same cycle , right ? I understand that charging happens in a very little time , so two cycles already is not shown on oscilloscope but in BoyleStad is explained...
  45. EinsteinKreuz

    Hardware Random Generators: Transistors vs Diodes

    So which method works better for random number generation(in terms of flatter frequency spectrum): transistor breakdown or Zener noise? I want to know whether to use a Zener diode or a Transistor when building a white noise generator. And FTR I intend to use Germanium because of its higher...
  46. Hassan Raafat

    LEDs: Connect 3 LEDs Without Microcontroller

    Is there is a way to connect three LEDs so that there are three cases where one LED only is working in every case of the three without using micro controller ?
  47. debajyoti datta

    Diode Configs: Same Work | Rectify Me Please

    2 diodes connected back to back ...and 2 anti-parallel diodes...are these 2 configurations same...i mean work similarly?...i think NO...rectify me please if wrong...it might be a silly question but i would really appreciate the answer
  48. Hassan Raafat

    Engineering Design a clipper circuit with a specific output

    Homework Statement Homework Equations Clippers equations The Attempt at a Solution I knew that we will put a two diodes( with a dc battery {2.3 V} series) parallel to each other in opposite directions .. but what meant by gain is 0.95 ?
  49. S

    Series connected zener diodes problem

    I have attached the image with post. Answer to question is given as A. I am not getting the explanation to how can one zener diodes be in breakdown and other not. I think if the combined voltage of 150V is applied then only breakdown occurrs in both the diodes simultaneously.
  50. Hassan Raafat

    How can I understand an OR gate with diodes?

    can i understand at OR gate with diodes , why o/p not equal the sum of two voltages (5+5=10v) , it's confusing me ?
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