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. J

    Understanding the Role of Resistance in an OR Gate Using Diodes

    http://www.tutorvista.com/content/physics/physics-iv/semiconductor-devices/logic-gates.php I don't know how to post a pic so please go to this site and look at the OR gate why is resistance R connected to the point C. I don't understand its use? I think the OR gate would function without it...
  2. Femme_physics

    Engineering Electronic circuit with Op-Amp, Switch and Diodes

    Homework Statement http://img689.imageshack.us/img689/6668/mycircuit.jpg Given a circuit that includes Operational Amplifiers, double-switch - S, for two situations, 1 and 2. Type of switch - DPDT - Double pole double throw. Two diodes and two lightbulbs, L1 and L2. Given: Voltage...
  3. Femme_physics

    Differential amplifier with zener diodes

    I think I'm getting better at this ((thanks to gneill, ILS, ehild and technician :wink:I'm quite sure I got it right using the easy methods (formulas). I'm not too sure about my "check up" to my solution using KCL and KVL...I didn't solve the check-up all the way because I wanted to see if my...
  4. S

    TVS Diodes for ESD Protection?

    I'm developing a basic cable continuity tester. Essentially, the circuit drives a test vector onto the cable and reads back the output vector. The output has MOSFETs for buffers/drivers but the input is connected directly to the ICs (CPLD, in my case). My concern is ESD. Unfortunately, I have...
  5. A

    Analyzing Diodes in Series and Parallel: Current and Voltage Calculations

    Homework Statement The reverse saturation currents of a Schottky diode and pn-junction diode at T = 300K are 5*10^-8 and 10^-12 A, respectively. The diodes are connected in parallel and are driven by a constant current of 0.5 mA. (i) Determine the current in each diode. (ii) Determine the...
  6. M

    Diodes - red & orange (light from one or both)

    Homework Statement Depending on which substances they're composed, light emitting diodes typically need 1.5 - 3 V in forward bias to give satisfactory light. You have two light emitting diodes, red and orange, you want to couple together in a capsule. You want to make a circuit where the...
  7. C

    Engineering Electric circuit with negative reference voltages and diodes

    Hi I am having trouble figuring out what to do with negative reference voltages in my circuit. I attached my problem(Problem 3) and I know that some current will be drawn out of the ground and I think all of the diodes will be on but I am unsure how to approach this problem.
  8. W

    Engineering Calculating Voltages in a circuit (With Diodes)

    Say D1 is a silicon diode( .7 volts) and D is a Germanium diode (.3 volts) Determine the voltages at A,B,C and D with respect to ground You can use hypothetical values Any help would be greatly appreciated Thanks
  9. A

    How to build a DC->AC converter using resistors capacitors and diodes (no inductors)

    How to build a DC-->AC converter using resistors capacitors and diodes (no inductors) I have been trying to learn electronics (I am familiar with the principles, just have no experience designing complex circuits to fulfill purposes), so I went to RadioShack, got myself: breadboard assorted...
  10. Femme_physics

    Transistors - Diodes with a perk?

    Are transistors essentially diodes with a perk? I mean, they do exactly what diodes do (one way valves) AND they can amplify current. Doesn't that make them more efficient? Why not make only transistors then? They appear to be always made out of the same basic materials, so I don't see the big...
  11. A

    Realizing AND & NOR Gates w/ Diodes: An Explanation

    logic gates perform the logic operation but how. please explain an AND and nor gate circuit realization from diodes.
  12. P

    Which Diodes Do I Need? - BestPCReviews

    Hey, I have flasher module installed and I wanted to have flashing corner lights and turning lights from the same wire. Problem is when I would use corner lights, the turning lights will be on too and when I would use turning lights, corner lights will activate too...
  13. N

    How are diodes made? Practical methods explained!

    please I want to know how diodes are made practically I searched for this in many seatch engines but I don't found any resukts that satisfies me I hope u could help thanks in advance
  14. K

    P-n junction diodes (Both bias)

    Given this picture, the circuit is put in reverse bias. Therefore the electrons are flowing INTO the p-type junction. - As electrons flow into the p-type material the depletion zone is raised as the p-side is made more negative. A picture from hyperphyics.phy-astr.gsu.edu illustrates this...
  15. B

    LED vs Plain Diodes: What's the Difference?

    This is probably a stupid question but here it is: I am just learning concepts of LEDs. To me, it seems that there is no difference between LED and normal diodes. In normal diodes in forward bias, electrons come from n type and recombine in p type right? In this process photon should be...
  16. I

    Carrier injection in p-i-n diodes

    Hello all I have a p-i-n diode structure. I am applying a forward bias to diode, so that holes from p region, and electrons from n region are injected inside the i region. Now, I need to find a relationship between the applied bias/current vs the number of holes and electrons that are...
  17. DaTario

    Diodes, transistors and valves

    Hi All Given that one has a basic understanding of the working mechanism behind the diode, how can one develop a comparison between diodes, transistors and the valve. Best wishes, DaTario
  18. S

    Full-Wave Rectifier w/ 2 P-N Junction Diodes & Transformer

    Show how two P-N junction diodes can be used in conjunction with a transformer that has two secondary windings, to form a full-wave rectifier. (Draw a circuit diagram including connections to the mains transformer). Explain the operation of your circuit using sketches of waveforms. (3 marks)...
  19. R

    Engineering Solving a Circuit with Diodes: Find V Across Resistor

    Homework Statement http://img832.imageshack.us/img832/6302/20285200.jpg Uploaded with ImageShack.us Homework Equations The Attempt at a Solution I'm unsure where to begin with this. I need to find the value V across the resistor and I'm unsure how. What effect do the diodes...
  20. D

    Light emitting diodes and Planck's Constant

    In my lab class we performed an experiment, in which we 'determined' the value of Planck's constant (value of h/e actually) by measuring the turn-on voltage for light emitting diodes of various colors. The idea is: Given a light emitting diode that emits light with a maximum wavelength of...
  21. F

    Understanding concept of Zener Diodes for voltage

    Hey guys I have a question about how zener diodes usually work as voltage regulators in circuits. To my understanding, one can place a zener diode in any circuit to stabilize the voltage to the zener diode voltages rating for the whole circuit. This makes sense for one zener diode. I...
  22. B

    Simple Diodes Q&A - Constant Voltage Drop & Output Regulation

    I have a fairly stupid question about diodes. Constant voltage drop means that, no matter how much i put a voltage on a diode, there will be always 0,6V drop on it? Can I use this a simple output regulator? http://pokit.etf.ba/get/3935756d6354860fdc6a3b72f60c66db.jpg
  23. T

    Can you add voltages in parallel if you use diodes?

    I'm sure you can't but I don't really see why not. Its been ages since I've done anything like this and I just wondered, I can't think of a way to varify it like I don't think you can use superposition theorm. My question is shown in tha attatched picture. Thanks very much.
  24. B

    Solving Diode Circuits: I & V for Ideal & CVD Models

    Homework Statement Find the current I and potential V for a simple diode circuit from the picture using a) ideal diode model b) CVD diode model (Vd=0,6 V) [PLAIN]http://pokit.etf.ba/get/36406f902c2c24bd8a3c4ffa8fe97b78.jpg Homework Equations U=RI I1+I2=I The Attempt at a Solution This diode...
  25. B

    Can Resistance Increase Brightness in LED Diodes and Light Bulbs?

    Hello, I did an experiment home, i took a power supply 9V and hooked it up in series with 1k Ohm resistor, then after that I hooked it up to a parallel connected 2 LED diodes. So both diodes were on the same voltage drop. I don't know exact calculations behind it but it doesn't matter. Here is...
  26. D

    Sketching Waveforms in Circuits w/ Diodes

    Homework Statement sketch the output waveforms when a 5Vp sine wave with a frequency of 100 Hz is applied to each of the following circuits **see attached diagrams** Homework Equations The Attempt at a Solution
  27. D

    Common Cathode Diodes: Safe to Use in Parallel?

    I know that using diodes in parallel is generally a bad design practice since you will have run away current in one of the diodes since they are not necessarily matched exactly. But is it safe to use diodes in parallel if they're designed as a common cathode part? this is an example...
  28. D

    How do diodes handle high current spikes when charging capacitive loads?

    If I consider a simple example of charging a capacitive load with a low impedance source, and charge the capacitor through a diode, I will have a very high current spike through the diode while the capacitor charges to the supplied voltage. When I look for diodes and see their peak pulse...
  29. E

    Transfer Characteristics of Real and Ideal Diodes (and more sources)

    I'm looking for information regarding the "Transfer Characteristics of Real and Ideal Diodes". I've tried google and the section on this site for learning material, but I've failed to find a site that displays both transfer characteristics and explains them. I was hoping that someone would have...
  30. J

    Diodes application in mechanical engineering

    can anyone give me some suggestions on the applications of diodes to our course? i'm not really familiar with machines that uses diodes. a simple example would be enough and highly appreciated. i'm just a 2nd year college student by the way.
  31. Q

    What Causes Electric Field Breakdown in P-N Diodes?

    i am not sure if this is considered electrodynamics under classical forum but oh well, here goes i was reading wiki about p-n diodes and its that for reverse bias diode, because of the anode attracting the holes WITH the cathode attracting the electrons, the depletion zone widens and causes...
  32. R

    Doubt regarding silicon waffers and silicon diodes

    Hi, basically i am confused about the characteristricts of silicon diodes and waffers. As i know the VI @ CV characterstricts of the diode. But i tested the same characterstricts with silicon waffers which behaves perfectly same as like diodes. Mainly i need to know about the difference between...
  33. R

    Doubt regarding silicon waffers and silicon diodes

    Hi, basically i am confused about the characteristricts of silicon diodes and waffers. As i know the VI @ CV characterstricts of the diode. But i tested the same characterstricts with silicon waffers which behaves perfectly same as like diodes. Mainly i need to know about the difference between...
  34. E

    Why are diodes heavily doped

    Can someone explain why in diodes one side of the junction is heavily doped, namely the p-side in a standard diode, resulting in a p+n junction? Or in an led where the n-side is heavily doped? I can't seem to find the reasoning behind this anywhere.
  35. E

    Why 2 diodes in series for full bridge rectifier

    A friend of mine builds tube audio amplifiers for a hobby. Being an electrical engineer, who works exclusively with micro-electronics, I thought I might mess around in spice a bit to better understand some of the standard circuit topologies they use. My friend is not an engineer so he doesn't...
  36. F

    Ideal Diodes in Series: Output Voltage (V0) & 1kHz 10V P2P Sine Wave

    I have been given this problem as a homework assignment. I need to find the output voltage (V0) given an input of a 1kHz 10V peak to peak sine wave. According to the answer manual neither diode conducts. My reasoning behind this is that when the sine wave is +10V diode1 is reversed-bias and...
  37. X

    Diodes in Tv / Microwave / Mobile ?

    Homework Statement Is there a diode in Tv / Microwave / Mobile ? if it is then for what purpose the diode is there ? Homework Equations I got an assignment to find the list of those projects in which diodes are used also mention the purpose of diodes in these projects , I've found 8...
  38. D

    Engineering Need help with a circuit with Op-amp and Diodes

    Homework Statement Hello, It would be very appreciated if someone could give me any orientation in this problem: The Attempt at a Solution (1) I do not understand very well how Vout is changed from -VDD to VDD, however, I wonder if the following would be ok... When Vout =...
  39. S

    Thermal to electric conversion with diodes

    There is well known phenomenon such as thermal current in diodes which is 26millivolts at room temperature.And it increases with temperature rise.How good are diodes in converting heat to electricity and what qualities should have diode for perfect heat to electricity conversion?I read that...
  40. C

    Understanding Thermionic Diodes: How Do They Work?

    I am reading about thermionic diodes and trying to understand how they work , it uses a heated cathode and the electrons are ejected from it via thermionic emission and i could see how the electrons couldn't go the other way because it would require a large voltage to get them off of a...
  41. L

    What are the applications of AND and OR gates using diodes?

    Homework Statement http://www.play-hookey.com/digital/electronics/dl_gates.html revered members, in the above link, for OR GATE, when either of the diodes are forward biased we get the output voltage as logic HIGH. but for AND GATE, when when either of the diodes are forward biased or...
  42. Sigurdsson

    How Does Voltage Affect Diode Behavior in a Circuit?

    The following picture represents the current/voltage graph through a basic p-n junction diode. Diodes have a built in potential 0.6 volts. One must overcome this potential to make the diode work. This 0.6V are the nearly flat line in the forward region. Am I right? My question is...
  43. S

    Full Wave Rectifier (2 diodes)

    Homework Statement A full-wave rectifier is operating at a frequency of 60Hz, and the rms value of the transformer output voltage is 15 V. (a) What is the value of the dc output voltage if the diode voltage drop is 1 V? (b) What is the minimum value of C required to maintain the ripple...
  44. FeDeX_LaTeX

    Will current flow in a circuit with two opposing diodes and a DC source?

    Hi; Consider this circuit (ignore my bad drawing): http://img63.imageshack.us/img63/3967/diodes.png In the picture there is one cell, two diodes and a bulb. Will the current get trapped in the second branch and continuously flow around that loop? Thanks.
  45. P

    How Does an LED Emit Light?

    In LED's(light emiting diodes),How does the light emit ? thanks
  46. J

    Analysis of a circuit that contains two diodes

    Homework Statement The diodes are ideal, so their internal resistance is zero. The zener diode has a 4V activation voltage. There is only one variable element in the circuit is V0. The question is what is Vab for every value of V0, and what are the directions of the current...
  47. D

    Diodes Current–voltage characteristic

    Homework Statement http://img39.imageshack.us/img39/7496/59187398.th.jpg VDON=0,7 First it is asked to calculate V0 for Vin=-1V and Vin=-5V. Secondly it is asked to draw V0(Vin) for -10<Vin<10 Homework Equations The Attempt at a Solution Using Kirchhoff Volt Law I've...
  48. C

    Microwave Diodes - Looking for manufacturer.

    Does anybody know any good manufacturers of microwave diodes? Specifically, I'm looking for rectification that can be operated at essentially as high of a frequency as I can get. This led me to look for Schottky diodes (anybody have a better suggestion?). So far, all the microwave...
  49. R

    Solve Thevenin & Diodes Homework with Ideal Diode

    Homework Statement http://img444.imageshack.us/img444/5601/scan0001my.th.jpg Hey, I'm trying to solve this problem using thevenin's method. As you can see in method 1 I was able to solve for the correct output voltage of 7.5 volts. When I try Thevenin's method I get 4 volts. I have a...
  50. E

    Zener Diodes Homework: Load Regulation

    Homework Statement A designer requires a shunt regulator of approximately 20V. two kinds of zener diodes are available: 6.8V devices with r_z=10ohms and 5.1V devices with r_z=30ohms. For the two major choices possible, find the load regulation. In this calculation neglect the effect of the...
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