Diode Definition and 570 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. D

    Extreme Fiber Coupled Laser Diode Power Loss

    What could cause a laser source with fiber coupled laser diodes to have extreme loss of power? The laser diodes have a wavelength of 658nm and have an output rated at 60mW but it seems as though the optical channels actually output ranges between 58 to 70mW. During some troubleshooting I...
  2. nothing909

    Engineering Easy zener diode circuit questions

    Homework Statement The Attempt at a Solution [/B] So basically, as the question says, you need to calculate the current in the zener and load when the supply voltage is 10V and then again when it's 15V. FOR 10V SUPPLY Voltage across resistor = 10-5 = 5v Supply current = 5/1000 = 5mA...
  3. E

    Engineering How to analyze diode circuits? (Find waveform generated)

    Homework Statement To analyze these circuits, we need to draw the current path right? I know that current can only flow one direction through a diode. http://i.imgur.com/kipBcax.pngHomework Equations N/A The Attempt at a Solution Are these paths correct? Green = positive, red = negative 1...
  4. R

    Connecting a Diode: Tips for Li-Ion 18500 Battery

    I've done my background research on this but i want to double check with others since the last time i did this i blew $30 because i shorted my diode. I got a new one but I'm really nervous about starting it up. These are the two parts...
  5. S

    Engineering What are these types of diode circuits?

    Homework Statement For each of the circuits, draw the waveform. The voltage drop across each diode is 0.7V Homework EquationsThe Attempt at a Solution I know that both of these are using diode bridges, but is there a specific name for these circuits? I think the waveform for Vo1 and Vo2 are...
  6. W

    From the Shockley Ideal Diode Equation derive....

    Homework Statement The Shockley idea diode equation is ##I = I_0( e^{\frac{qV}{kT}}-1)## (1) Where ##I_0## is the reverse bias saturation current, ##q## is the charge of an electron, ##T## is temperature in Kelvin and ##k## is Boltzmann's constant. For large reverse voltages, ##I## is...
  7. moenste

    Resistance of the resistor and of the diode

    Homework Statement A semiconductor diode and a resistor of constant resistance are connected in some way inside a box having two external terminals, as shown in the diagram below. When potential difference of 1.0 V is applied across the terminals the ammeter reads 25 mA. If the same potential...
  8. B

    Find thevenin equivalent resistance with diode.

    Homework Statement I have a circuit with a diode in it. I have to find the thevenin equivalent in order to reduce the circuit to a DC source, single resistor and single diode. How do I account for a diode when trying to find Rth and Vth? Do I just remove it and have it act as a short circuit or...
  9. K

    What Is the Ideal Resistor Value for a Diode Circuit Using Load-Line Analysis?

    Homework Statement Determining the best resistance for my simple circuit consisting of a diode, battery, and resistor. Doing this using Load- Line Analysis Homework Equations ID = VD - V / R - Given by KVL[/B] (I can disregard n-pretend ) The Attempt at a Solution [/B] Here I have...
  10. U

    Why Are My Diode IV Characteristics Readings Different?

    I was doing an experiment to plot the IV characteristics of a diode. I connected a resistor, diode and milli ammeter in series. I connected a voltmeter across the diode. I measured the diode voltage and diode current. When i changed the resistor, I got a different set of diode voltage readings...
  11. Dr. Manoj

    PN Junction Diode: Diffusion vs. Drift Current

    What exactly is difference between diffusion current and drift current?
  12. Dr. Manoj

    Zener Diode Breakdown: Effects on PN Junction & Holes/Electrons

    Once the zener Diode is formed by breakdown of pn junction Diode, potential across Diode remains constant. If we again change the configurations from reverse bias to forward bias, is it possible to get back the normal pn junction as before the breakdown and will potential across junction be...
  13. Fayyaz Ahmed

    Reverse Bias in Semiconducter diode

    Why don't we consider the current produced by voltage source in plotting reverse bias characteristics?if this current is considered then the saturation current will depend on the the external voltage.
  14. B

    Engineering Zener voltage controlled circuit design

    Homework Statement Homework Equations V0=Vsrz/Rs+rz+VzoRs/Rs+rz-ILrzRs/rz+RsThe Attempt at a Solution I formulated 4 cases for voltage inputs of 11 and 13.6 V and 0 to 100 mA. The zener current has to be between 3 and 30mA or 103 and 133mA. How can the current be maintained in thes two...
  15. B

    Finding voltage change for current change for diode

    Homework Statement Find the change in diode voltage if the current changes from 0.1 mA to 10 mA. Ans. 120 mVHomework Equations V2-V1=VTln(I1/I2)The Attempt at a Solution That is all the information given. The only equation I can think to use is the diode voltage/current relationship, but a...
  16. M

    Amplifying a Photodiode using an OpAmp

    Dear electrical engineers, Here a question from a serious electronics n00b =D. I tried to build a system as shown in the image. I have a photodiode which gives me a clock signal in the range of 200 to 500mV. Frequency will be in the range of 100 to 1000 Hz. I would like to amplify this...
  17. S

    Why is There a Factor of 2 in the PIV Rating for a Full-Wave Bridge Rectifier?

    Homework Statement Part C of the problem below. I have the solution but I don't follow the logic. Homework Equations Turns ratio: Vp/Vs = Np / Ns KVL I do not think I need any elaborate formulas to solve this. The Attempt at a Solution Solution Provided by instructor: I am confused why there...
  18. Gbox

    Engineering Diode circuit with AC excitation source

    Homework Statement Graph ##V_{out}## Homework EquationsThe Attempt at a Solution When ##V_{in}=V## C1 is positive on the left and negative on the right, and C2 is negative on the the down side and positive on the upper side so there is no Vout?
  19. A

    Why does the voltage drop across a diode change with increasing current?

    Homework Statement I have recently performed an experiment where the voltage drop and current through a diode were measured. I am wondering why the voltage drop across the diode changes. Theoretically, the voltage drop should stay the same as there is a certain amount of energy required to get...
  20. nathanxx6969

    Current Across Diode for DC Sources: 0.86mA

    Homework Statement :Find the current that go across the diode ans=0.86mA[/B] Homework Equations V=IR 3. The Attempt at a Solution The Vt(v total) is 30v so,must i ignore the diode as off first?.In that case the current is 30/20=1.5 mA. i also know the that diode is foward bias because...
  21. P

    Find the Schottky diode barrier height and the ideality....

    Homework Statement Using the diode equation with moderate forward bias, show numerically how to find the Schottky diode barrier height and the ideality factor via a graphical plot. Homework Equations I = I0e(eV/nkT) I0= AA*T2e-eφb/kT with n= ideality factor and φb= Barrier height The Attempt...
  22. M

    Voltage across reverse biased diode

    Hi all, I think I know the answer to this question but I'm having trouble explaining why it is so. If I have a circuit with a fixed resistor connected in parallel with a reverse biased diode, I believe the voltage drop across each will be the same. Is this correct? If so can someone explain the...
  23. D

    Engineering Diode - RC circuit differential equation

    Homework Statement I'm having difficulty deriving the differential equation, this is what I have so far. In order to solve it, I will be using Matlab, and I'll be using the equation dy/dx ≈ (y(x + dx) - y(x))/dx. Is my derivation correct so far? Homework Equations In picture. The Attempt at a...
  24. S

    Are there purely diode, vacuum tubes?

    I am looking for a very simple and specific vacuum tube. It doesn't have to be high power. I only need a plate that completely surrounds the cathode. No grids would be ideal. Anyone have a parts number or link for something similar to this?
  25. kamhogo

    Light bulb & Diode: linear or non-linear elements.

    Homework Statement These questions are related to an experiment where we had to record the current for varying values of potential difference (10 readings), then repeat the process with the applied potential difference was reversed a) Why is the resistance of a light bulb not constant? b) Does...
  26. A

    Diode Use in Relay: Why & How to Protect Op Amp

    Why reverse diode is used in relay ?? In my book its written that ,to protect op amp from damage but how does it protects?
  27. debajyoti datta

    Diode Configs: Same Work | Rectify Me Please

    2 diodes connected back to back ...and 2 anti-parallel diodes...are these 2 configurations same...i mean work similarly?...i think NO...rectify me please if wrong...it might be a silly question but i would really appreciate the answer
  28. P

    Potential Difference Across Diode & Resistor

    Homework Statement Assume an ideal diode with ##V_t=0.6##v, find the potential differences across the diode V_ab and across the resistor V_bc as the forward bias voltage is varied from 0 to 10v. Hint: equivalent circuits may be useful Embedding the image wasn't working so...
  29. N

    Understanding Basic Diode Questions

    My understanding is that a diode conducts current if the voltage at its anode is larger than the voltage at its cathode. I don't understand this. 1) Once the diode begins conducting current, the voltages at the anode and the cathode are identical (the diode serves as an open wire). Therefore...
  30. H

    How to determine the breakdown voltage of a diode?

    Homework Statement The question is posted below. Homework EquationsThe Attempt at a Solution I don't know how to solve this question.Does the breakdown voltage of a diode depends on the voltage source near the diode?For example,breakdown voltage of D1 in (a) is 30V? Also, I don't know how to...
  31. Marcin H

    Which diode will turn on in this circuit?

    Homework Statement Homework Equations V=IR The Attempt at a Solution I'm not sure how to figure this problem out. At first I was thinking that the diode on the left would turn on because that segment of wire has less resistance than the wire with the second diode. Current flows where...
  32. D

    Question about pn diodes and their lifetime

    I was wondering, does the lifetime of a diode depend on how long it takes for all the free P electrons to transfer over to the p holes? In other words, do the electrons that fall into the p holes ever return to the n side?
  33. Weightofananvil

    Zener Diode Problem: Solutions and Guidance

    Hey, I'm studying zener diodes and the various ways they are used. This question is throwing me for a loop however. I can't get my simulator to display the circuit like it is in this question because it only sets reverse breakdown voltages @ 5mA. I'm just wondering if I'm on the right track.If...
  34. n.easwaranand

    Zener diode : Calculating the series resistance

    Homework Statement : [/B] Given a voltage regulator with 6.8V Zener diode, input voltage range of 15-20V and load current range 5mA-20mA. Calculate the series resistance R for the regulator.Homework Equations : [/B] Applying KVL and no load situation, we get R = (V - Vz)/Iz where V is the...
  35. T

    How Do You Calculate Diode Current in a Circuit with Second Approximation?

    1. So I have a voltage input of 12V, resistor 1 of 2k ohms, and resistor 2 of 4k ohms. These are connected to a diode and a load resistance of 1k ohm and load. I am instructed to use second approximation 2. The problem wants me to find load voltage, load current, load power, diode voltage...
  36. M

    How to Choose the Right Diode Size for Your Off-Road Lights | Expert Tips

    Hey guys, brand new to the forum and have an electrical questions or you guys. I can work my way around wiring but only the basics, I tried to do a search but with my knowledge I came up empty handed So here's the background I'm trying to find what diode size my buddy needs for his truck, He...
  37. T

    Diode Resistance: Electric Field & P/N Junctions

    Hello, A diode is represented by an EMF equal to the electric field in depletion zone plus a resistance. This resistance is obtained from the I/U characteristic of a diode. My question is, this resistance is due to what? The resistivity of P and N junctions or because in forward bias case...
  38. cnh1995

    Built-in voltage of pn junction diode

    Why can't the built-in voltage of diode be measured by a voltmeter when the diode is isolated? A potential difference of almost 0.7V exists at the junction, which is clearly not too small for the voltmeter to detect. What's the reason?
  39. N

    From where we measure current in a pn junction diode

    Please anyone explain me from where we measure current or we apply ammeter in a pn junction diode to measure current
  40. Amal Thejus

    How can the neutral regions in a diode have constant potential?

    Homework Statement It is said that the potential in the neutral regions of a PN junction diode is CONSTANT. Homework Equations V=Q/4ΠΣr The Attempt at a Solution It is said in all textbooks to ASSUME that the electric field in the neutral regions as zero. Two aspects confuse me. 1. What...
  41. Amal Thejus

    ACTUAL Variation of Potential inside a diode.

    Homework Statement The figures showing the potential variation inside a PN junction normally shows the potential to be constant in the neutral P and N regions Homework Equations V=Q/4ΠΣr The Attempt at a Solution Since the potential due to the positive and negative charges should also exist...
  42. H

    Can a Zener Diode with a Breakdown Voltage of 1V be Fabricated?

    Hello I must complete my research before Saturday... my problem is: how can we fabricate a zener diode with lower than 5.6v zener voltage? a curve in my reference book determine how much doping need to manufacture desirable zener voltage. but the minimum voltage we can achieve is about 2.5v in...
  43. K

    Understanding KVL Loop in BJT Biasing and Calculating Ve

    Please help how Ve is calculated what i think is that it should be: -Ve=-Vee+IeRe; How Ve is taken positive please someone draw equivalent circuit for same
  44. STEMucator

    How Can I Identify a Metal Diode with Specific Voltage Requirements?

    Hi everyone, I'm looking for a metal diode that has a maximum reverse breakdown voltage of about 11.500 V and a turn on voltage of about 0.750 V. Below is a plot of the reverse linear IV characteristic where the metal diode is marked by an orange dot. Below that is a plot of the forward...
  45. Ascendant78

    Question about current flow and diode?

    Ok, I'm trying to simulate a circuit containing a diode and I am a bit confused. I thought the arrow direction on the diode symbol shows which direction the current is able to flow through it. However, in my simulation, it is showing that the diode is limiting current flow in the exact...
  46. DeldotB

    Diode Equation and Saturation Current

    Good day all: For the diode equation: I(V)=I_{sat}e^{\frac{Ve}{nKT}}-I_{sat} I also know that the second term in the equation is negligible if: V> > nV_{T} Vt is thermal voltage n is ...just a factor related to the quality of the material I have these initial conditions: V> 0.1V\, \, \...
  47. R

    Zener Diode Clipping Graph Help

    So we started looking at Zener Diodes in our electronics course. What I am having trouble with is the interpretation of the graph. For the example our diode has a Zener Voltage is 6.2V. I understand what happens in the positive half but when the direction changes is where I get confused. Why...
  48. brainbaby

    The use of diode in this circuit....

    please help me guys My inference to above circuit... The negative cycle of the output signal from the driver is entirely clipped off before getting to switching transistor..this however don't have any effect on output because the transistor won't conduct for negative cycles but when due to any...
  49. P

    Graphing the V vs I relationship of diode using Square wave

    Homework Statement I am having trouble understanding what this picture is showing. [/B] I know that in the case of a sine wave, the voltage below zero will not conduct much if it does not drop past the breakdown region. On the other hand, it will start to conduct and grow exponentially at...
  50. A

    Understanding the Breakdown Voltage of a Zener Diode

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