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. H

    Dc resistance of silicon diode

    Homework Statement The dc reistance of a silicon diode for a current of 10 mA is closest to: Homework Equations Really not sure. The Attempt at a Solution Not sure where to start, this goes with a lab I just completed but not sure if this problem directly correlates to it.
  2. R

    Pulsing a 2W Laser Diode w/ 26 AWG Wire - Is Gauge Okay?

    I am going to be pulsing a laser diode at around 2 Watt (room temperature) with a frequency of around 1-10 MHz. Right now I'm planning on using 26 AWG wire. Anyone have any thoughts on whether this is okay? Is the gauge okay? Since it's pulsed I assume I don't have to worry as much about heat...
  3. H

    Calculating Diode Current with Is=50nA and Vd=0.6V | Homework Help

    Homework Statement Determine the diode current with Is=50nA and an applied forward bias of 0.6V Homework Equations Id = Is ( e ^ (kVd/Tk) - 1) The Attempt at a Solution So my teacher is horrible and this is what I have been able to collect on my own. Is = 50 and Vd = 0.6v I'm...
  4. L

    Solve Electric Diode Problem: Find I & V

    Homework Statement Find values of I and V for the circuits of figure; assuming that the diodes are ideal. http://yfrog.com/081034op Picture: http://img8.imageshack.us/img8/3026/1034o.png Homework Equations I can use KVL/KCL. And have a rough knowledge of finding wheather a diode is on or...
  5. T

    Ok to use MOSFET body diode as flyback protection?

    Hello, I am designing a motor controller, and I was curious about the MOSFETs I'm using that have an internal body diode zener for Vds protection that is common in a lot of datasheets. I am switching the coils of the inductor with these MOSFETs, and I would like to know if its unwise to...
  6. M

    What Affects the Forward Voltage Drop of a PIN Diode?

    hii... you all know about IV Characteristic PIN diode.. I fabricate PIN diode and want to analysis my result.. what is the forward voltage drop for PIN diode? are the voltage fix o variable.. ??
  7. F

    Engineering Diode Limiter Circuit: Input-Output Graph & Voltage Output

    Hello, I have recently had a lab on diode limiters and am a bit confused by the results. The circuit is seen in the picture below and I have obtained theoretical values for the Voltage output. The circuit is feed by a 16V sine wave with a frequency of 1kHz. Now I know when the sine wave is...
  8. M

    Fabricating PIN Diode with Boron, Si and Phosphorus

    Hii... I already fabricated PIN diode using boron (P), Si (N-type), and phosphorus (N). For the method, I etching two contact at Si wafer then doping the boron and phosphorus... there are width I-region (Si) between the contact. A already measured the I-V characteristic of PIN diode but...
  9. F

    Engineering Solve Ideal Diode Circuit - Find V & I

    Hello, I have been given a homework problem about ideal diodes. The diagram is below. I need to find V and I. I have the solution (4 mA and 1V) however I am unsure as to why it is so. I would have set 5V at the node where the resistor and 3V diode meet therefore setting all the diodes to be...
  10. V

    How do I calculate the current in a diode?

    Homework Statement The question I have been set is "Calculate the current in a diode when the forward voltage is 0.62V and the reverse saturation current is 10pa." Homework Equations I really have no idea how to begin solving this one. The only equation that I have been taught...
  11. G

    Engineering Diode Circuits: Find Q-Point for D1

    Homework Statement For the figure below, use the ideal diode model and the constant voltage drop diode model (assume a turn on voltage of 0.6V) to find Q-point for diode D1: [PLAIN]http://gotejjeken.webs.com/ckt.jpg Homework Equations KCL/KVL The Attempt at a Solution For the ideal model, I...
  12. S

    Why diode is not demon of Maxwell?

    Diode should conduct electrons in one direction only. Why doesn`t it produce power at ambient temperature or any temp.?
  13. N

    Engineering DIY Diode Clipping Circuit: +10/-10V Supply

    Homework Statement Hi. I'm being asked to make a circuit to take the input waveform, on the left, and extract the output waveform on the right. In my circuit, I can only use basic diodes, resistors, and DC supplies of +10 and -10V. The Attempt at a Solution
  14. W

    Solving Zener Diode Problem - Need Help

    Homework Statement Please refer to the picture [PLAIN]http://img337.imageshack.us/img337/7118/46864828.jpg Can anyone help me? Thanks.
  15. H

    Eye Safety: Laser Diode Recommendations

    Can anyone recommend a good laser diode that won't cause damage to the eye with prolonged exposure?
  16. X

    Reverse Bias: Diode, Resistor, Voltage & Current

    In forward bias the supplied voltage is distribute among the resistor and the diode (diode and resistor are connected in series) but in reverse bias the Current across the resistor remain zero because the conduction starts when very high voltage is supplied ...am i right ? but why the Voltage...
  17. T

    Engineering Power dissipated in R (zener diode circuit)

    Homework Statement A zener diode runs off 10V and supplies 5V to a load that draws 100mA. The minumum zener current = 5mA. R = 47Ω What is the dissipation in the resistor if the output is short-circuited? Homework Equations None. The Attempt at a Solution Using R = V - Vz / Izmin...
  18. S

    Electron and hole contributions to the current of a diode

    Having some trouble with this question. I don't even know where to start to be honest. Any help/pointers greatly appreciated. Thanks! Been working on this for a while now and have found a possible relevant equation to add. Am I heading in the right direction? I don't even know what each term...
  19. R

    SiC diode: History, Characteristics & Temperature Effects

    Hi all, Can anyone brief some history and the Characteristics of SiC diode. I having difficulties to find the infomation about the SiC material. Beside that, how the Temparature related with the I-V curve (Eg: 200k, room temp,600k) and different between the Si and SiC at room temp? Thx.
  20. X

    Projects in which silicon and germanium use as a diode

    Homework Statement Where can i study about those projects in which silicon and germanium use as a diode with their purpose in the appropriate project? The Attempt at a Solution I want the list of atleast 30 projects in which si & ge , i also wants to know for which purpose si & ge use in...
  21. W

    Zener Diode Regulator: Why Output Voltage Drops?

    My teacher was talking about power supply voltage regulators. I cannot get why does a zener diode regulator's output voltage drops after the load current through it exceeds some critical current? thanks in advance :smile:
  22. T

    Zener diode ballast resistor question

    Homework Statement Determine the value of the ballast resistor is satisfactory if a 5Volt 0.5 watt zener diode is used in the circuit sorry can't upload a picture but basically VS = 15v min to 20v max R ballast = 90 ohms (series with zener) and R load (in parralel with Zener) is 50...
  23. K

    What is the current through each ideal diode in this circuit?

    Homework Statement find current through each diode, suppose that they are ideal (use the second approach) [PLAIN]http://img30.imageshack.us/img30/102/86772682.jpg R is 10kohms The Attempt at a Solution a) (12-0.7)/10k = 1.13 mA b) 0 because diode will be open, actually i added up the two...
  24. A

    Diode Switching Characteristics

    Homework Statement We are given a peak-to-peak voltage of 10. I am attempting to explain the following characteristics: 1) With a larger forward bias (and a corresponding smaller reverse bias), the storage time increases. 2) With higher frequency, the storage time decreases...
  25. R

    No problem, glad I could help!

    what are the differences between Zener diode and pn junction diode characteristics CURVE?** the breakdown process is easier in terms of breakdown voltage for zener diode. as, it is highly doped.
  26. T

    What diode should I use for my motorcycle's dual headlight setup?

    I need to know what diode to use for the following spec: I need to use this for my motorcycle. I have 2 xenon headlamps working on my bike but 1 lamp lits up for low beam and the other for high beam, now I need to light up both which means I've got to use a diode. Need to know which is the...
  27. Z

    Diode -> Plug conversion help.

    So I have this lighting fixture that I'm trying to plug into an outlet. I took the diode and tried connecting it to and old phone plug. This didn't work. [PLAIN]http://img52.imageshack.us/img52/6803/20100608201408.jpg I was wondering if plugging this into an outlet is even possible, and...
  28. M

    Doubt in semiconductor diode theory ?

    doubt in semiconductor diode theory ? hello friends :smile:... in this picture diode is forward biased. positive terminal of battery repel holes n negative repel electrons , finaly electrons n holes recombine n eliminate each other. but its said that current flow is due to electrons ...
  29. S

    Calculating Current and Voltage in a Diode Circuit

    Homework Statement I have the following circuit: [PLAIN]http://elementdesign.sk/dioda.jpg I would need to calculate the current and voltage through the diode. I now that I can calculate the current by the following formula: I=I_{0}(e^{U/U_{0}}-1) I know that I_{0}=10^{-17} and U_{0}=20mV...
  30. N

    Why does a diode have a specific sign?

    why diode has such a sign?? by the bottom sketch we have the diode to be short circuit but if we look at the upper sketch we see that the current (ie electrons) flows from the plus p side for diode to be short circuit we ned to have the electrons flow to the n side not to the p side...
  31. I

    Effect of ntype/ptype dose increase on the pn diode breakdown.

    Hello, I was hoping someone could answer my question. So i am wondering ..lets say i have a p-n diode. What happens if i increase the dose of the p-side of this junction . What happens to the reverse breakdown of this diode? People say that the reverse breakdown decreases when you increase...
  32. L

    Zener diode as voltage regulator

    Homework Statement revered members, this circuit i have attached is for voltage regulation using zener diode. applying kirchhoffs current law i get current through resistance R is IR=IZ+ IL And the voltage drop across the resistance R is V-VOUT HOW this equation of voltage drop is...
  33. L

    Voltage regulation using zener diode

    Homework Statement when zener diode is used for voltage regulation, voltage source is connected in series to zener diode and load resistance is connected parallel to zener diode. when zener diode is reverse biased, it will enter zener breakdown region. when input voltage increases zener...
  34. M

    Designing a Stepped Attenuator Using Pin Diode Switches in Microwave Office

    i am designing a stepped attenuator using pin diode as a switch in microwave office. i am having difficulty in using pin diode as a switch. i knw it is operate in forward bias and open in reverse bias. if i am giving a rf signal between 300 Mhz to 3 Ghz then how can i switch it to reverse bias...
  35. T

    P-N Junction Diode Problem HELP

    Homework Statement A pn junction diode has saturation current Is= 1e-12 A. What is the current through this diode if a positive voltage 0.68 V is applied to it? (Unit: A) Homework Equations I=Is(e(Vd)/(Vt))-1) The Attempt at a Solution I don't even know where to begin, but i just...
  36. S

    Forward Bias in PN Diode: Explained

    Probably a really stupid question but for a pn diode in complete forward bias i.e 6volts (switch on 0.7volts), does it behave like a normal resistor or is it a squared resistance till say 200 volts and is there a forward voltage breakdown mechanism. I can only find I V curves that got to about...
  37. DryRun

    What Does This Diode Symbol Represent?

    Homework Statement I have looked in all my textbooks but i can't find anything about this diode or what it does? Here is the symbol of that diode (from a City & Guilds past exam paper): http://img5.immage.de/2204diode.jpg Homework Equations It's just an unknown diode symbol to me, and there...
  38. R

    P-n junction diode open circuit electric field

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  39. Z

    Analysing Op Amp Circuit with a Photo diode

    For a lab we built the following circuit. Our photo diode was receiving a blinking signal which our op amp made visible on a DVM. I do not understand the purpose of the capacitors attached to the power rail. So far I understand how negative feed back with the Rf resistor controls the amount...
  40. C

    How Does a Zener Diode Stabilize Voltage in a Circuit?

    well first i saw this solution of a zener diode problem on net A 5.0v stabilised power supply is required from a 12v d.c. input source. The maximum power rating of the Zener diode is 2W. Load resistance = 1 kiloohm Using the circuit above calculate: circuit ...
  41. D

    How does reverse bias affect leakage current in a diode?

    My question is related to the leakage current occurring in a diode when connected in reverse bias mode. When the diode is forward biased, the source voltage first neutralizes the barrier potential and then the flow of current occurs. However, I am not able to understand how the current due...
  42. Z

    Predicting Output Voltage Using Small Signal Diode Model

    small signal diode modelling i understand what it is but when i get asked a question like: if vin(t)=2.5+cos(2*pi*100*t) for 0<t<30 use the small signal model of the diode to predict the output voltage of the circuit i have added. assume the opamp is ideal R=2000 Is=10e-16 so i know...
  43. D

    Current in Diode: Electrons vs Holes

    My question is related to the flow of current in a diode. In a metal, the current is completely due to the flow of electrons (Eventhough, we always consider the conventional direction for current). Whereas, the current in diode is said to be the sum of the component of current due to holes and...
  44. ¡

    Double check base resistance values and TVS diode choice, please.

    Yo yo yo. What up homies? I am once again humbled to be in need of your gracious assistance. I did all the work this time. I would just like some fresh minds to double check. I am driving two relays with http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=FMMT493CT-ND" is the...
  45. J

    How Do You Design an RF PIN Diode Switch for High Isolation?

    Hi, This is my first encouter with anything to do with RF design. I'm trying to design an RF PIN diode switch to meet certain specifications. I'm having considerable difficulty putting together a circuit schematic that will accomplish this. My specs are: Center frequency: 15GHz Bandwidth...
  46. S

    Diode clipping at a given threshold

    First post, after tinkering with electronics so long I just had to join a physics oriented forum. I'm trying to work out how I can get an input voltage to "clip" at a certain level. I start by imagining an ideal diode (no current on reverse bias, infinite current on forward bias). My setup...
  47. R

    Engineering Complex Diode Circuit: Solve DC Output, Ripple, Rating & Power

    Homework Statement Consider the following power supply circuit, which uses typical component values. The diodes have a forward drop of 0.6V each. Transformer voltages are RMS (root mean square). http://img294.imageshack.us/img294/1665/70454661.png a. Determine the DC output voltage...
  48. C

    Questions about Silicon Diode Detectors

    I have some questions about how silicon diode works, specifically as a ionizing radiation measurement instrument. I will write what my understanding is so far from different textbooks/websites (please comment whether I have it correct) and also write question where I get confused. Thank you...
  49. R

    Leaner question : what is the purpose of this diode in the diagram?

    Hello experts, :!) The following is a diagram posted by a learned forummer and i like to find out what function does the diode serve for the coil of the relay. http://www.flickr.com/photos/46348930@N03/4400589307/ Thanks for reading my question. regards Ramone
  50. X

    How Do You Add a New Diode Model in LTspice?

    EDIT: PROBLEM SOLVED! I found a model on a website of the manufacturer! Next, I need to hunt down this 5.1 V Zener. Hey. I'm designing a full-wave bridge rectifier regulated by a Zener, and on of the project requirements is an LTspice simulation(not to mention it's a good place to start before...
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