Diode Definition and 571 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.

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  1. 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...
  2. 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...
  3. 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...
  4. 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...
  5. azizlwl

    How Does the Depletion Region Influence Diode Behavior in Forward Bias?

    At depletion layer of p region, there more negative ions thus negatively charged region. Likewise at n region, it is positively charged. Then why in equivalent forward bias the diode behave as a battery of .7v with positive at depletion region of the p region where it is negatively charged?
  6. V

    Radiation Diode Detector Doping question.

    I'm reading up on semiconductors and there seems to be a few fundamentals I cannot find answers for if anyone can help? I understand that n-type substrate is doped with a donor and p-type substrate is doped with an acceptor creating excess electrons and holes. When you put the p-type and...
  7. Femme_physics

    How can a diode defend the coil during transistor cutoff?

    http://img252.imageshack.us/img252/6080/photo46k.jpg Once the transistor is at cut-off, it means Ib and Ic = 0. I don't see what the diode has to do with anything in terms of "protecting" another component. Can anyone help me see that?
  8. E

    Operating Point of a 1N4148 Diode

    I recorded statical characteristic for sc diode 1N4148 at T=300K. How to determine operating point of diode and plot both in matlab?
  9. P

    Engineering Logical diode circuit description

    Homework Statement i.imgur . com/tjtAC.png (Sorry! It's fine I promise!) I was given this circuit and I need to know what exactly what kind of circuit it is. i.e. what kind of logical operation it performs. V_o is the output. IN1, 2, 3 are the inputs. I need to know the states of conduction in...
  10. T

    A diode with a resistor in parallel and in series.

    I have a diode with a resistor in parallel(R2), but also diode resistor circuit has a resistor in series with it(R1). I have uploaded a drawing as well but I think it takes a bit of time for them to be authorised. The values of the circuit are Vs = 20v R1 = 3kΩ R2 = 470Ω Diode = Has a Volt drop...
  11. B

    (Reverse) Schottky Diode Question

    Is a reverse Schottky diode possible? I understand the basics of the Schotkky barrier/rectifier commonly achieved by a metal/semiconductor interface. Recently, it was suggested to me that a "reverse" Schottky junction is possible if the metal is placed against a fully depleted, high...
  12. Y

    Analysis by assumed diode states

    Homework Statement I'm having a hard time trying to figure out where to start. I know I have to assume the diode states and then calculate if the assumptions work within the circuit. The Attempt at a Solution None as yet because I'm never sure where to start on these circuits...
  13. Y

    Please explain how the MOSFET and the diode work.

    I have been working on some music electronics, I got this on the web and I don't understand how the clipping circuit with germanium diode work. 151334[/ATTACH]"] The part in question is the enhancement mode MOSFET IRF510 with the 1N34 diode. It is a clipping circuit common in distortion box...
  14. S

    Understand Diode Connected MOSFET Circuit

    Hi, Can you please let me know how does the attached circuit work? Vh and Vl are inputs ; Vbn and Vbp are outputs. Thanks in advance.
  15. Femme_physics

    Can a diode light up when it's connected backwards?

    http://img560.imageshack.us/img560/453/14led.jpg Trying to find the answer to the question if a regular basic LED diode can light up when it's connected backwards? I even made a lil' sketch
  16. C

    Calculating Is and nVt for Silicon Diode, How?

    Hello, everyone! I was asked by my lab instructor for an Electronic course to conduct a diode experiment by which I can get the value of (nVt) and saturation current (Is) for that diode. I did the experiment by connecting a DC power supply in series with a forward-biased silicon diode...
  17. A

    Minority carriers in a Schottky diode

    Say I have a schottky diode with n type semiconductor. Why can't electrons from the metal flow to the valance band of the semiconductor? If I reverse bias the schottky diode, the valance band may be higher than the fermi level at the contact, and electrons should be able to flow from metal...
  18. Q

    MATLAB [Matlab] Ideal Diode (Vector Graph)?

    Hello, I am a novice in an introductory engineering problem solving course using matlab, and I'm having a bit of a problem. I have attached a screenshot. I know this is supposed to be pretty basic stuff, But I am hung up on it. Now, what I have so far: t=(0:0.01:10)...
  19. S

    Diode i-v characteristic via oscilloscope

    Hello all, We utilized a differential attenuator to display the i-v characteristic of a 1n4005 diode. However, I was a bit confused as to how I could determine what the y-axis was calibrated as. I know that the vertical axis is actually current, but is there some sort of tactic for determining...
  20. N

    The use of a reversed biased zener diode in voltage regulator

    Hello. I asked this question because I am confused of the use of a reversed Zener Diode in voltage regulator even after I built the circuit using MultiSim. I don't understand why we should put a zener diode right there and how it works. I looked at the I-V plot of the Zener diode and I know...
  21. L

    Diode paralell with a resistor problem.

    Today my teacher asked us a question Basically he said a match box was taped shut and a current was passed through the circuit a reading came up on the Ammeter, then the cell was switched around, and a current ran through the circuit but the Ammeter read a smaller reading than before. Why?
  22. E

    How to Choose the Right Shottky Diode for Transistor Switching?

    Hey guys, I ordered some shottky diodes to speed up a transistor switching. The diodes I ordered don't work for me; I will upload a waveform with the diode if it would help. It was mentioned in the other thread HERE about needing a "signal" shottky as the ones used for power had a large...
  23. F

    Pn junction, diode and energy level of conduction band during forward biasing

    Hello Forum, I am looking at the energy levels between the n and p regions of a diode. The p-side has a conduction band that starts at a higher energy (same for the valence band). The n-side has the valence and condution bands that are at lower energy. The Fermi energy line is the same...
  24. S

    What happens in a circuit that has a capacitor in parallel with a diode?

    I attached a PNG of the simple schematic. I know that the cuircuit should shift the waveform that's coming from the source. What i don't understand is why or by how much it will be shifted up. Any help in explaining this is appreciated.
  25. A

    Diode voltage drop (connected in parallel with a resistor)

    Hello, I am a computer engineer that specialized more in software but I am trying to remember the electronics part. In the book I read there is an exercise where a diode (forward-biased) is connected in parallel with a resistor and then both of them are connected in series with another...
  26. S

    Two questions about the dynamics of a laser diode

    I am using a laser diode to count aerosol particles flowing through a gas stream. The refracted light is being funneled to a photo-multiplier via fiber optics. When there is no gas flowing (and therefore no particles) we are seeing some strange results from the output signal of the...
  27. A

    Simple Diode Analysis Problem - Calculating Current/Voltage in a diode:

    Homework Statement Refer to the figure attached. Let IS = 25 fA and VCC = 10V. What is the total current, the current in the diode, and the current in the 5KΩ resistor? What is VD? Use the iteration technique. Homework Equations Ideal Diode Equation: I = Is(e^(Vd/Vt) - 1) Ohm's...
  28. S

    Wrong measuring of diode I-V curve in pulsed mode

    Hi. In order to measure the I-V curve of a normal diode in pulsed mode, I set up the following experimental kit. The experimental results do not change with pulsewidth, which is quite long (us regime), and low frequency (200hz and less). An HP pulse generator is connected via BNC cable to an...
  29. Y

    Any free simulation programs for transistors, FET and diode circuits?

    Hi, I've been busy in designing some circuits and I want to simulate some non linear behavior of transistors and diode circuits. I want to find a free simulation program. Does LT Spice work on these discrete components? Thanks Alan
  30. W

    Is there such a thing as an inverted zener diode?

    Zener diodes act like regular diodes, except that they allow current to flow in the reverse direction if the voltage is high enough. That is, current with voltage ABOVE a certain value will flow. My question is, is there such a diode that only allows current to flow if the voltage is BELOW...
  31. J

    Why Does a Zener Diode Withstand Reverse Biasing When Ordinary Diodes Fail?

    Hey everyone! I was just wondering why a Zener diode doesn't get damaged whereas an ordinary p-n junction diode does, when reverse-biased under sufficient voltage. In both diodes, when reverse-biased, there is a dislodging of valence electrons of the host atom. So, why does this damage the p-n...
  32. F

    Question About Diode Voltage Drop

    Say the voltage drop of a diode is .7 volts. Once the voltage drop has been reached, and it begins conducting electricity, can the voltage be backed off to around .3 volts and it will continue to conduct electricity? Or does the amount of electricity need to be a constant .7+ volts?
  33. A

    Physics P-n Junction Diode Problem

    Q:-Find the current through the resistance R in the figure:- , if the value of R is:- a.12Ω b.48Ω. Assume resistance offered by diode is 0 in forward bias and ∞ in reverse bias. Homework Equations Ohms Law:- V=RiThe Attempt at a Solution I tried using kirchhoffs law but we don't know its in...
  34. Z

    Reversed bias diode with applied voltage

    hi there i just have a question about diodes say for example we have the following cct: the circuit with the diodes with the 5V supply, one of the diodes is on and the other off and i understand why this happens but when dealing with the circuit the opamp and the diode i am confused. the...
  35. O

    SCR and Diode are Active or Passive Components?

    Hello! SCR and Diode are Active or Passive Components? Please clarify the definition of Active and passive components. I have some confusion in it! Regards otoman
  36. C

    Voltage Source, Inductor, Flyback Diode & Switch Circuit

    In a simple circuit consisting of nothing more than a voltage source and inductor (with flyback diode in parallel) and a normally closed switch...i understand that when the switch opens the magnetic field collapses and the inductor starts to build up voltage in opposition to the change in...
  37. S

    Can You Design a Diode Circuit to Turn On at 5V and Off at 15V?

    Homework Statement Given an input range of voltages (for example, 5-15V), design a circuit using resistors and diodes (and voltage sources) to turn on at input = 5V and turn off at input = 15V. (I chose 5 and 15 arbitrarily).Homework Equations The Attempt at a Solution I am able to get it to...
  38. R

    Using an L.E.D. as a diode to control current flow?

    I'm trying to make a small crystal radio and have managed to wire up the antenna and the head phone jack but I haven't got any diodes suitable for the voltages I'm using. I have some LEDs but will these dissipate too much current or cause any harmonics or interference with the signal?
  39. Femme_physics

    Op-Amp basic problem with a LED diode

    Homework Statement http://img822.imageshack.us/img822/1859/theque.jpg Given the following circuit, including an Op-Amp and a LED diode. The voltage on the LED diode is 1.4 Volt. In your solution assume that the Op-Amp is idealHomework Equations (In the solution...) The Attempt at a Solution...
  40. N

    Graph Vo vs Vin: Zener Diode Behavior

    There is a variable Vin which goes through a resistor to a node (Vo) which then branches through a diode to a 3V source or to ground through a Zener diode. I'm to sketch the graph of Vo as a function of Vin. -4V < Vin < 4V The resistor is 1K The diode is CVD model, Von is .7V, Vzener = 2.7V...
  41. S

    Engineering Help Analyzing Circuit Using Ideal Diode Method

    Hey guys, I see this website a lot when lot when looking for help so I made an account since I cannot find help with this problem anywhere. Homework Statement Use the ideal diode model to analyze the circuit below (circuit (a) in the attachment). Start by assuming D1 is off and D2 is on...
  42. B

    Inductor, switch, snubber diode(flyback diode)

    Hello, I am designing a simple circuit and I need some guidance over snubber diode. When we open the switch, when we have a inductor in circuit, we will have that arc over switch which is something that we don't want. Using this snubber diode, we can avoid this. I feel that we will...
  43. hagopbul

    I am buying a laser diode but cant understand some parameters

    i am buying Pulsed Laser Diode in Plastic Package 25 W Peak Power SPL PL90 and there is some parameters about semiconductors lasers... Forward current = 40 A why all this current ? then in the catalog Reverse voltage= 3 Volt then they say the Threshold current = 1A ? what is the...
  44. B

    Op-Amp Precision Diode: Eliminating Voltage Drop

    [PLAIN]http://pokit.org/get/3deef3b185bf6b18007a25ddc18ce7d5.jpg So I have another thread running on op-amps, and while waiting for mr. Jiggy to come back online, I want to ask another op-amp question. This precision diode. I understand what is the point, and why it is so useful...
  45. T

    How tell what Amps in a drop down volt diode

    Hi I working on a 2 cell lipo pack and need to drop the volts from 8.4 to under 6 volts. I have been using diode to do this but now I need to know what amps it will handle and which diodes to use. the setup I have now runs one servo that might pull 0.25 amps but now going to a system that will...
  46. E

    Help needed working out a zener diode circuit's total Voltage

    Here is the circuit- Can someone please tell me why the lamp will always have a voltage of 20v across it no matter how high the voltage is? Doesn't the zener diode allow voltage through it after 20v? So then only the voltage after 20v has been dropped should go through the lamp right? For...
  47. E

    Why Is the 0.7 Volts Diode Drop Used in Calculating R2 Current?

    This isn't a homework question but it is a formula from a book I have been using to study, so I'm posting it here. Here is the circuit and formula - I don't understand why the voltage drop of 0.7 volts across the diode is being used as part of the formula to work out the current...
  48. F

    Series resistance of Schottky diode

    Homework Statement I have plotted the I-V characteristics of a Schottky diode under strong forward bias (0-0.7V, conduction begins at about 0.3V). I have to find the series resistance of the diode, rc. Homework Equations My notes give the equation...
  49. D

    Calculating Minimum Power Source for Zener Diode Shunt Regulator

    Homework Statement A zener diode D1 is specified to have Vz=3.8V and a knee current of 100 microamps. It is used as a shunt regulator where the minimum load resistance is 6.2k. What is the minimum power source that ensures that the shunt regulator remains regulated? Homework Equations...
  50. L

    How do I find the forward resistance of a diode using diode law?

    Homework Statement I must find the resistance of a diode inside the piecewise model using the diode law equation. I am given variables VD = .75V, Is = 5*10^-13 A, and VT = .026 A. n = 1Homework Equations The Diode Law equation: ID = IS(e(VD/nVT) - 1)The Attempt at a Solution We were told...
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