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. A

    Understanding the Breakdown Voltage of a Zener Diode

    Why doesn't the voltage vary beyond breakdown voltage in zener diode?
  2. A

    Which kind of diode to handle flyback voltage?

    Lately I've been rediscovering my old interest in electronics and in my own time I've been looking through some tutorials on various things I decided to go ahead and build one, an H bridge circuit for a 5 volt DC motor. My question is I'm not clear on which diode I should use as flyback diodes...
  3. G

    What happens when collector-base voltage is 0 in transistor?

    Hello I'm now studying current mirror and have a question about replacement of diode to transistor as shown in the attached image. The upper image is original current mirror circuit shown in study document. Collector current IC is very similar to current through Rbias thus current to load can...
  4. K

    Determine the reverse saturation current for the diode

    Determine the reverse saturation current for the diode below, given that VS = 5V, R = 360Ω produces a diode current of 10mA. Use h = 1.3 and VT = kT/q = 25mV. I believe this is the formula needed. Id = Is(e^(VD/(h*25mV))-1) The problem I had was I've done several questions similar to this but...
  5. T

    Reverse Recovery Current of a diode

    Hello, When the diode is in forward bias phase and suddenly we apply a reverse bias voltage, the diode takes time to be fully blocked because of the excess of minority charges that are stored in P and N region. Thus a reverse current appears in the diode for a short time before it is blocked...
  6. A

    AXIS P1355 Camera I/O + relay to turn on light/garage door

    here is the manual http://www.axis.com/en/files/manuals/um_p1355_49956_en_1303.pdf see page 61 Notes: i have seen this thread https://www.physicsforums.com/threads/axis-camera-with-i-o-and-relay-to-turn-on-lights.538043/ but this camera is a bit different i think as it has digital inputs and...
  7. D

    What are high field domains in GaAS diode?

    Homework Statement Can someone explain me what are high field domain or can give me a source from where I can understand it.It will be very helpful. Homework EquationsThe Attempt at a Solution
  8. F

    Understanding Diode Current Flow: A to B or No Flow?

    Homework Statement What is the current flow when a diode is connected in series with a resistor and battery.The cathode of the diode indicated as A is connected to the positive battery terminal.The Anode of the diode indicated as B is connected to the one leg of the resistor and the other is...
  9. A

    Electric Field in Capacitors and Diodes

    Hello, Capacitor When a capacitor is connected to a voltage source, electrons will move from one plate and accumulate in the other in accordance to Q=CV. Due to the imbalance of charges (positive and negative ions) between the plates, an electric field exists that flow in the direction of the...
  10. I

    Engineering Analyzing diode circuit with Constant Voltage Drop model

    Homework Statement Homework Equations Whenever assuming a diode is "on", replace that diode with a 0.7 voltage source. Whenever assuming a diode is "off", replace that diode with an open circuit. The Attempt at a Solution The problem is pretty straightforward but the format of the circuit...
  11. S

    Why do the free electrons in the N-type want to diffuse?

    I'm trying to understand how a diode works and for this I've used(among other resources) the book written by Albert Malvino, Electronic Principles. Everywhere I read about this topic, it says that when the N-type and P-type semiconductors are joined together, the free electrons from the N-type...
  12. Salvador

    Flux diode, magnetic semiconductors

    So I was reading about magnetic semiconductors and I got confused so can you please clarify I will ask a question that is made up of two parts. Magnetic semiconductors are ... a) devices that alter or switch on/off electric current flow depending on the magnetic field strength etc applied OR b)...
  13. A

    What is the polarity of a Pn junction diode

    Hello all Textbooks teaches us that in the formation of Pn junction in between P and N type semiconductor a region is formed where free electrons of N diffused in P side and exhaust by the holes of P near the junction. Such a region becomes devoit of free charge careers and their are only ions...
  14. R

    Diode Modeling Pt 1: Open & Short Circuits

    Homework Statement Homework Equations Model diode in reverse direction as an open, model diode in forward direction as a short. The Attempt at a Solution In part e of the question, does the circuit stay in state 1 after it gets into state one or does it change states?
  15. STEMucator

    Some quick ideal diode analysis

    Homework Statement Find the currents and voltages indicated for the circuits given: Homework EquationsThe Attempt at a Solution I needed some practice, and I want to ensure I understand for the harder problems later. (a) The diode is going to behave like a short circuit, so the current...
  16. STEMucator

    Engineering How Do You Calculate Resistance in a Diode Circuit for Specific Voltage Changes?

    Homework Statement Design the circuit in the following figure so that ##V_o = 3V## when ##I_L = 0## and ##V_o## changes by ##20mV## per ##1mA## of load current. (a) Use the small-signal model of the diode to find the value of ##R##. (b) Specify the value of ##I_S## (saturation current) of...
  17. gracy

    How do you make Zener diode connections for different types of diodes?

    Homework Statement :[/B] I don't know how to do connections.I just know how to do it in specific type of zener diode because i have learn this.I don't understand these connections.Within 30 minutes i have to leave for my exams please help.Homework Equations [/B]The Attempt at a Solution -[/B]...
  18. Rampart

    Engineering Zener diode circuit-variable voltage source

    Homework Statement This diode zener has breakdown voltage equal to Vz=8.2V for currents: 75mA<=iz<=1A.If RL=9 Ω,how much must Rs be,so that VL=Vz=8.2V,while Vb changes at about _+10% in relation with the nomimal operating current,displayed in the data sheet which is 12V? The Attempt at a...
  19. N

    Does a CFL Pose a Fire Risk Due to Inductive Load Characteristics?

    As far as I know, Compact Fluorescent Lamp (CFL) is an inductive load. I understand that inductive load doesn't allow an immediate change in current. When the circuit was initially open (through open switch) then became close, the inductive load was energized. So opening again the circuit after...
  20. P

    Diode forward voltage in datasheet

    hi, On a diode datsheet, is the value quoted as the forward voltage the same as the cut-in voltage?
  21. N

    Follow-up question about my understanding on rectification

    I understand the process of rectification but just only in theory. But I still have questions that I guess will be answered if I can experience or has experience about it (but sadly I don't have). Please kindly answer these questions: 1. Does the waveform of Vout can be considered as DC (...
  22. A

    Troubleshooting PN and Zener Diode Circuit Fluctuations: Tips and Solutions

    When pn and zener diode is connected according to the circuit diagram(manual not diode box,ie, by connecting wires) it shows great fluctuations and readings can't be able to take. What may be the reason for this and how can i rectify?
  23. P

    Understanding Diode Barrier Potential and Its Role in PN Junction Diodes

    Hi, For a PN junction diode, am I correct in thinking that the barrier potential (due to depletion region and hole-electron recombination etc.) is the same as the 'forward voltage' quoted on datasheets? Also, when a forward bias condition is created and the applied voltage is greater than the...
  24. Q

    Finding output of voltage for certain input voltage diodes

    Homework Statement We have the circuit in the figure.I have to find the output graphically if the input is Vi=15sinwt. Homework Equations This type of exercise doesn't have any equations The Attempt at a Solution Heres the circuit http://i.imgur.com/ivixWzH.jpg For Vi<= -10 the diode is ON...
  25. L

    What happens to the minor charge carriers in p-n junction diode

    what happens to the minor charge carriers in p-n junction diode when forward biased?
  26. U

    Diode Polarity: Anode, Cathode, Forward Bias

    What is meant by diode polarity. If we do connect anode to positive and cathode to negative then its means it works on Forward Bias mode. I think positive means higher potential than negative, in other words, if positive terminal which is Anode is to be at 5 volts and negative terminal which is...
  27. gracy

    Why Isn't There More Current in Reverse Diode?

    I am not getting why there can't be (or very negligible )current in reverse diode.According to this image positive terminal of battery would suck electrons from n-type and pass them to negative terminal of battery.And Negative terminal would provide electrons to p type and from there we can see...
  28. N

    Pn junction diode (series combo of voltage source and diode)

    The question is to solve the current through a resistor after a pn junction. (photo attached) As far as I'm aware the voltage source in the pn junction is (in this orientation) of opposite polarity to that of the 0.8V voltage source. From my understanding the answer goes like: V=IR I=V/R...
  29. T

    How is the Electric Field Established Inside a Diode When Voltage is Applied?

    Hello, When a Voltage is applied to a diode, how the electric field is established inside the diode? Is it the same as a resistor which surface charges density establish electric field inside it? Thanks
  30. W

    Engineering Diode Circuit Analysis: Get Expert Help Now!

    < Mentor Note -- Thread moved to Homework Help from EE forum > hi guys I am studying on diode circuit but i cannot really analyse a circuit with a diode. I understand that the question is asking minimum Vout so the current source input should be -2.5mA but i cannot go beyond that. Can anyone...
  31. Steven Ellet

    PN-junction diode vs light emitting diodes

    Is it advisable to use an LED instead of a PN-junction diode and what is the resistance of each (or do they vary)? The only reason I'm asking is LEDs are easier and cheaper to get. P.S. What I need it for, only needs a PN-junction diode.
  32. Rampart

    Engineering Ac Circuit Ideal Diode: Find Vout-t

    Homework Statement http://prntscr.com/51us65 the diode is ideal.What i need to find is the Vout-t Homework EquationsThe Attempt at a Solution check my solution in pdf and guide me if you can... ***In my approach,in the circuit i forgot to draw the line.It is supposed to be a short circuit,not...
  33. Hylton Conacher

    Choosing a Diode for 12V Battery Charger: Tips and Recommendations

    Just joined and looking for information on which diode to use to protect a 12V battery charger circuitry connected to a battery. it is charging. Should the mains supply fail ie battery charger has no forward current, the battery may apply voltage and current to the circuitry damaging the LM338...
  34. M

    How Does an Ideal Diode Affect Voltage in a Circuit?

    Homework Statement 1a) Use an ideal diode model and find V in both cases. Show your work. (I would assume an ideal diode model means with a "perfect" u-i characteristics?) A diode circuit is as shown: 1b) If V1 = 2.8sin(t), sketch to periods of V1 and V0 in the same graph. Use an idea...
  35. P

    Solving Diode Equation for Current?

    Homework Statement I need to find the current, but not sure how to rearrange the equation because of the I in the exp. Homework Equations The Attempt at a Solution Thanks, just need to be pointed in the right direction. Seems like I will either be in ln or exp.
  36. Femme_physics

    Why is there an extra diode in this sketch?

    Hey guys, I'm trying to wrap my head around this electronic schematics of a PLC, because I've started ladder-programming it. Can anyone explain to me why are there TWO diodes before the transistor? I get that one diode shows an "active" or "inactive" state when it's turned on or not. But why...
  37. A

    How Do You Use the Incremental Model to Analyze Diode Circuits?

    Homework Statement Homework Equations r_d= V_T/I_D, V_T=25mV The Attempt at a Solution i alreayd find the operation of diodes, D1 off and D2 on (2nd circuit). the current through this diode i also calculate as 34mA, also r_d=0.7353 ohm. I am having trouble using incremental model, in my book...
  38. A

    Engineering What Value of V Results in This Junction Diode Circuit?

    Homework Statement (circuit attached) If the circuit shown, D2 has 10 times the junction area of D1. What value of V results? To obtain V=50mV, what current I2 is needed? Homework Equations I = I_S * (e^(V/V_T) - 1), V_T=25mV I(D2)/I(D1) = e^((VD2-VD1)/V_T) The Attempt at a Solution If D2 has...
  39. L

    Zener Diode Q-Point Calculation

    The Q-point for the Zener diode in the figure given is ?
  40. L

    Diode numerical (calculation of current and voltage across diode)

    The Diode in the circuit shown below has the non linear terminal characteristics as shown in the figure.Let the voltage be "coswt" V . Question 3.1.33 and my attempt is shown in the figure.
  41. Q

    Zener diode exercise solved by me,is it correct?

    Homework Statement We have Vz=6.8 V and Iz=5 mA,rz=20 Ohm,Izk=0.2 mA, R=200 Ohm and the source V= 9 volt a)Find the output voltage when we have the input voltage with the nominal value of 9 Volt. b)Find for the nominal value of the voltage,which is the maximum load current for which the...
  42. kmm

    Why is there no current in a reversed biased diode?

    I understand there is some "leakage" current in a reversed biased diode but I don't understand why there is significantly less current in a reversed biased diode. I've seen the band diagrams and if all the electrons were only on the n-side of the diode, I would understand why the electrons can't...
  43. P

    Ripple factor in half wave rectification diode

    Please Help. I am not getting the concept of ripple factor in half wave rectification with the help of diode.The derivation done by our lecturer is not clear.Someone please explain the concept and its derivation. Also it seems from the derivation given by our lecturer that there are two types...
  44. perplexabot

    Can I buy pre-made balun transformers for a double balanced ring diode mixer?

    Hi all. I started a thread a while back about RF mixer design. I didn't know what to do or what design to choose. You guys laid some options for me and after some research and time I have finally decided that I will go for a double balanced, ring diode topology. Here is a schematic from google...
  45. meenu

    Reverse saturation current in zener diode

    What is the order of the reverse saturation current before breakdown in a zener diode ?
  46. ranju

    Finding Output Voltage, Resistance Drop & Current in a Circuit w/ Zener Diode

    In the given circuit we have to find the output voltage , the voltage drop across resistance RL (RL = 10KΩ) and the current through the zener diode having zener voltage VZ = 50V By this question I want to be clear about the way to solve circuits with zener diode...please explain the...
  47. NATURE.M

    Flyback diode to prevent back voltage

    So I am currently using TB6612FNG motor driver (see https://www.sparkfun.com/products/9457) to drive two dc motors. Now I wanted to connect a flyback diode (1n4001) to prevent any potential damage to the motor driver that may occur from the back voltage of the dc motors after I terminate the...
  48. ranju

    Zener diode characteristics question

    As I have studied that when the reverse voltage across zener diode is less thsan the zener voltage it is replaced by open circuit..now in the given fig. (input voltage 100V & zener voltage=50V) we are not knowing the voltage across the reverse voltage across the diode..but in its solution it is...
  49. C

    Confusing yet simple looking problem - DC analysis of diode & xstr

    Homework Statement DC analysis is required for the question in attachment. Vz=6V B=100 Vbe=0.7V Homework Equations The Attempt at a Solution I tried to find the result using the currents that were defined by the transistor. I found a result that was nonsense, the base current...
  50. S

    Spintronic light emitting diode

    A new spintronic LED was invented by Utah physicists. http://unews.utah.edu/news_releases/utah-physicists-invent-spintronic-led/ I thought that electron and hole suppose to recombine if electron is in exited state which means electron-hole pair is not in thermodynamic equilibrium with...
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