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. L

    Graph Vout vs Vin of diode circuit

    Homework Statement [PLAIN]http://postimage.org/image/bd4pyoqkt/ Make a sketch of Vout vs Vin for Vin from 0 to 5 V, assuming that both diodes have a diode drop of 0.5 V Homework Equations None that I know of. The Attempt at a Solution The way I see it, the Vout will start at...
  2. ElijahRockers

    Can I Transform Diode in Parallel for V_out vs. I_in Graph?

    Homework Statement Graph V_out as a function of I_in Attempt: I was able to complete the previous three questions by doing norton-thevenin source transformations and getting a single voltage source, which let me figure out the appropriate value of I_in for which the diode operates. But...
  3. W

    Forward bias in a silicon p-n junction diode

    Homework Statement The forward bias current I in the diode described (silicon p-n junction) varies as a function of the voltage V and temperature T described by the formula I = I_s*|e^[(|e|*V]/[n*k_b*T]) - 1| where |e| is the fundamental charge, k_b is the Boltzmann constant, I_s is the...
  4. T

    Zener diode as voltage regulator.

    The following link is a picture of my zener diode set up with variable load resistor. The Source is 15VDC and the first resistor is a constant 330 ohm. When I use 470ohm up to 15Kohm for the Load resistor RL, I get a 6V voltage drop across the diode. However, when I go down to 330 ohm for RL...
  5. H

    Piecewise Linear Modeling (diode)

    Homework Statement A pn junction diode is connected to a Thevenin circuit consisting of a 0-to-1V, 1kHz square wave and 1kΩ resistor. Use piecewise linear modeling to estimate the diode voltage for the low (0V), and high (1V) states of the voltage source. Assume the diode to have an...
  6. C

    Is the Voltage at Point A Still 5V with V_in at 0 in a Transistor-Diode Circuit?

    I just wanted to see if I am understanding this circuit correctly. Let's say the input voltage (V_in) is 0. This means: 1) no current through the 1000 ohm resistor 2) no 0.7V drop from the base to emitter 3) transistor is pretty much off 4) The circuit is open, thus no current goes through...
  7. C

    Circuits with Diode: Understanding Ideal Diodes and Their Behavior

    I have attached the problem along with the answers. I have a question on both of the questions. For the first question, if the diode is ideal, does that mean it's automatically "forward biased?" The problem statement says "assume the diode is ideal (i.e. has a 0V forward bias voltage)...
  8. T

    How to Analyse a Diode Circuit: Understanding Voltage and Current Relationships

    I'm a quite confused as to how to analysie a diode circuit How would I go about analysing the following? I know that I need to analyse the circuit with the diode on(short circuit) and off(open circuit).
  9. K

    AC Voltage across diode waveform

    I am wondering how the waveform of AC voltage measured across a diode would look like? What about the waveform of the resistor connected in series with this diode? Please help .
  10. P

    Engineering Incremental analysis to solve a circuit with a Zener diode

    Homework Statement The attached figure is an illustration of a crude Zener-diode regulator circuit. a) Using incremental analysis, estimate from the graph an analytical expression for v0 in terms of V and Δv. b) Calculate the amount of DC and the amount of AC in the output voltage using the...
  11. P

    Voltage output for ideal diode (solutions wrong?)

    I'm looking at some solutions for a problem I found. This link is http://www.etcs.ipfw.edu/~lin/MET487/2011-SumII/Lectures/Hw3_Sols-MET487-Sum2011.PDF It's page 4 problem 3.1. Okay so V_in is given to be 10cos(2∏t), but their graph for V_in makes no sense to me and consequently, V_out...
  12. A

    Solving Diode Conduction Homework with KCL, KVL, V=IR

    Homework Statement Use the approximation that the diodes conduct only at the indicated forward voltage. For what values of R is D2 Conducting and not conducting? Homework Equations KCL KVL V=IR The Attempt at a Solution I really am not sure how to approach this problem, as none...
  13. R

    Drift Velocity in a Vaccum Diode

    Is the standard equation for drift velocity of electrons also applicable to conduction in, say, a vacuum tube? I assume it is, and if so what is the relation between the drift velocities at the interface of vacuum-metal at the anode of a vacuum diode? The current, electronic charge and Area...
  14. A

    Potential difference across a diode

    Why is the potential difference across a conducting diode zero?
  15. X

    Understanding Diode Conductivity: The Role of Conduction and Valence Electrons

    As we are told in the books，a diode can be conductive by a forward-bias of about 0.7v. Thus,current through the n region is formed by the conduction electrons（free electrons in the conduction band） toward the junction.But in the p region,current is formed by the valence electrons from holes...
  16. R

    Can anyone provide data on the CY20F high voltage diode?

    Hello. I search, unsuccesfully, the datasheet for this component which is 20 kV diode. If someone has any data about it ...
  17. W

    Warming a laser diode using a thermistor

    I use a green laser pointer at night to do astronomy related work. I got a cheap $5 green laser pointer off of ebay, and when it's a warm summer night, the device works fine. However, the second it touches the cold, it fizzles out and gives me almost zero output. My idea was to use a...
  18. V

    What will happen if two ends of diode are joined?

    Here i am discussing about diode made up of p-n junction. what will happen if we join two ends of diode? Due to diffusion, there is a potential difference across depletion region.if we consider this as a battery(can we do so?) then there will be flow of continuous current through the external...
  19. D

    Is This Diode Circuit Analysis Correct?

    Hello everyone. Can you tell me if i solve right this circuit? D2 is on off mode so I2 is approximately 0,D1 is the same and D3 is on ON mode so the equivalent circuit is like AFTER. Is it ok what i did? http://postimage.org/image/mblq1dr7n/
  20. N

    Engineering Confirming Diode Current Flow in Circuit

    Is there any current flow through the diode in this circuit (attached) ? My initial answer was that there was none but then again I just wanted to confirm because all the other questions don't have any current flowing through them either. Looked fishy/
  21. O

    What is happening inside the zener diode ?

    Refer to this graph http://www.reuk.co.uk/What-is-a-Zener-Diode.htm The zener diode First the reverse biased set up then the depletion layer become bigger and bigger because the anode of the battery will attract the electron in n-type , leaving a lot of holes there. For the cathode, it will...
  22. E

    Engineering How to Analyze a Diode Circuit with Multiple Voltages

    Homework Statement Find voltage at Vo1 and Vo2 The left part is the schematic used in the question. The right side is the engineering schematic I drew up. The Attempt at a Solution I'm not sure what to do here. because there is a Si and Ge diode that means the Ge will be actived first...
  23. M

    Zener diode application suggetions

    Hi, I recently bought 10 Zener diodes the last time I purchase circuit elements. I was wondering if anyone had simple circuits or projects I could do, that needs zener diodes.
  24. S

    Engineering Circuit Analysis of a Positive Offset Clamping Diode Circuit

    Homework Statement Plot the waveforms for capacitor voltage VC, output voltage Vo, and diode voltage Vd given that Vs is a 20 Vpp triangle wave with period T. Use CVD model with diode VON = 0.7 V. Homework Equations KVLs? The Attempt at a Solution From my basic...
  25. G

    Comparison between bulk and ac resistances of a diode.

    Hellow guys! I find this concept really confusing, if the bulk resistance of a diode is an approximation of the I-V characteristic curve for a diode, Why then is that bulk resistance compared to ac resistances of the same diode at a particular operating in calculated values, seem not to...
  26. haael

    Is it possible to have a magnetic diode?

    I wonder: do there exist "magnetic semiconductors" and magnetic diodes and transistors? Normal electrical semiconductors rely on the fact that there are positive and negative charge carriers. Magnetism does not have monopole charges, so it will not be possible to construct an isolated region of...
  27. B

    Installing LEDs in footwells, will a diode work?

    I’m trying to install some LEDs in my footwells. I have a pink wire, which is my positive, and a gray wire, which is my negavtive. This is a negative switched circuit. So, is it ok to hook it up like this? 1 Positive of LEDs to pink, negative to gray. 2 Then, use a diode on the gray...
  28. S

    Engineering Diode Circuit ON/OFF Model Problem

    Homework Statement Homework Equations When Diode is on Vd=0.7 V and Id=0 When Diode is off Vd<0.7 and Id>0The Attempt at a Solution I've been working on this problem for hours now but I just can't logic it out properly. I know the right model is supposed to be D1 ON and D2 OFF, but I can't...
  29. A

    Three terminal high voltage zener diode

    Good day all, I am looking for a three terminal (zener based) shunt regulator IC that can handle at least 125V. If anyone knows where I can find it please post the url so that i can check the specs. Thank you
  30. I

    What is a Zener Diode? Understand Voltage Absorption

    I think I sort of understand, does it take all of the voltage in apart from a certain amount? so say you havea 4v zener, does it absorb all the volts but the 4? I've googled it but I really need to ask questions to understand.
  31. E

    Engineering Voltage drop across a diode in a high-amperage circuit

    I'm given a strange single-diode circuit where you must find out whether or not the diode is on. See the top diagram in the linked image: http://i.imgur.com/y1sn3.png (Current source is indeed 1 Amp, not 1mA as the 2kΩ resistor would suggest. Please do not try to correct the initial question...
  32. M

    How does zener diode maintains constant voltage ?

    hello friends , In zener diode due to high doping ,electric field is very intense .So this electric fields knocks electrons from atoms and reverse current starts flowing during reverse biasing. its said that at the same time it maintains constant voltage . Of which voltage we are talking...
  33. M

    Is This Statement About Zener Diodes Accurate?

    Do u agree with the statement given in picture i have attached about zener diode. i have taken this snapshot from a book on electronic devices.
  34. P

    Zener diode help (self-learning)

    sorry just found out this is the wrong thread
  35. W

    What diode do I need for automobile turn signals with LED's

    Hello, I have LED's all over my vehicle. I have them as tail lights, in the climate control,door switches, and several more throughout my car. I have this piece called a HYPERFLASH harness hooked up in the system that was recommended to prevent hyperflash, and it has done a perfect job...
  36. M

    Diode running into the resistor

    http://www.itisff.it/dip_eln/tda2030.pdf Couple questions. 1. In the Typical Application diagram on the left there is Vi w/ a 22k resistor. Appears that there's a diode running into the resistor and then the resistor goes to ground. The question is how should I interpret that? The...
  37. V

    Why does the width of depletion region is small in highly doped diode?

    Dear, In Zener Diode, In highly Doped diode,the breakdown(Zener breakdown) occurs in small voltage.How? Thanks& Regards, Viswanathan.M
  38. H

    Junction diode - unequally doped sides

    Why does the depletion layer penetrate a lightly doped side of a p-n junction diode?? Consider that there is a lightly doped p-side and a heavily doped n-side in a p-n junction diode , which is connected to a dc power supply in reversed biased. Now, I've read that depletion layer penetrates the...
  39. Femme_physics

    Engineering Why is a bridge rectifier necessary in this circuit?

    I am told that in this circuit (above pic) we shortcircuit D1 and D2, and disconnect D3 and D4... then we are to calculate Vrl(average) But the way I see it, if we shortcircuit D1 and D2 the entire circuit is shortcircuit and current only flows like this (below pic)...
  40. baby_1

    Can use Carbon to create Diode

    Hello Can use Carbon to create Diode instead of Silicon-germanium ? if yes why we don't have carbon diode? what is advantages and disadvantages?
  41. I

    Is resistance of a silicon diode constant?

    In our experiment we measured the forward resistance of a diode using a multimeter. We used that value and the voltage across the diode to compute the current passing through the diode. Is that value really constant??
  42. R

    Understanding Charger Circuits and Diode Voltage Drop

    Dear Experts I just connect a diode to a battery rated at 4.2 volts. The diode takes about 0.8volts ( i thought should be 0.7v but measurement says 0.8v) and the battery is currently at 3.12v. The supply voltage is 5v dc. After some time, if the battery reaches 4.2v, would current...
  43. E

    ZEMAX Help for coupling Diode Stack

    Hello! So I've been working on a project to couple a 15 bar diode stack into a 600 micron fiber. Using an old design that I've used in the past but it's giving me some issues. I don't have a plethora of experience with ZEMAX so I'm hoping to leverage the collective consciousness of the...
  44. L

    Diode Voltage Across D1: Solving for v(t) in Positive and Negative Cycles

    Homework Statement What will be the voltage v(t) across diode D1 ? Homework Equations The Figure is shown in the attachment. The Attempt at a Solution When there is a positive cycle D2 will be open circuit and capacitor 1 will be charged and diode D1 will be short circuited...
  45. Femme_physics

    Understanding Zener Diode Operation

    General basic electronics questions I have 3 questions QUESTION 1 -------------- http://img35.imageshack.us/img35/4011/zener.jpg No matter what value of R I have, as long as the source voltage (16V in our case) bigger than the zener's diode voltage specification (6V in our case), the...
  46. berkeman

    Anybody know of a 100mV Schottky diode or similar device?

    I need to bias the inputs to a transformer-coupled communications receiver apart by about 100mV. Since the transformer has split windings, one way to do this would be to add a Schottky diode into the center tap, and bias it with a little current (not enough to saturate the transformer). I...
  47. U

    PN junction diode barrier potential attracted to free electrons or holes?

    I am wondering about the barrier in PN junction diode.Due to diffusion negative ions are formed on the P side and Positive ions are formed on the N side of the diode.both opposite sides exert force of attraction and so a line of positive ions and negative ions align along the junction. The...
  48. N

    Free wheeling diode and contactor's contacts

    free wheeling diode for protecting contactor's contacts..in locomotive . . Is the free wheeling diode can protect the contactor contacts from opening sharp spark? The contactor is used in power circuit of dc series motor.. We always change these contacts bcuz they aging the sysetm consist...
  49. O

    Conceptual short circuit diode / zero-bias base collector junction BJT question

    Why exactly is there zero current flowing through a diode when it is short circuited, given the presence of the barrier potential? My current understanding is that the drift current precisely balances the diffusion current. But if you take a diode and short it with a wire, wouldn't you then also...
  50. M

    Light Emitting Diode (LED) Driving 10km Waveguide

    Homework Statement A Light emitting diode (LED) drives a single mode waveguide that is 10 km long, and has a material dispersion of – 100 ps/km/nm for wavelengths near 800 nm. The LED radiation has a spectral width of 60 nm and is centered at 800 nm. a) If the LED is pulsed on and off in 5...
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