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. Guessist

    Question for Schottky diode

    I studied semiconductor basic long time ago... So I've reviewed these days. For a while, i got a question about Schottky diode's frequency response. That is Schottky diode has more awesome frequency response than pn diode. Why does Schottky diode has good frequency response? Somebody help...
  2. anorlunda

    What is the right diode for connecting batteries on a boat?

    I want to connect a lead-acid starting battery to a bank of deep discharge batteries on my boat via a diode. The purpose will be to let the start battery charge from the same source, but to not back feed. First, I'm unsure how to rate the diode. 12v is maximum voltage, that's clear. But...
  3. I

    Engineering Understanding Diode Circuit Analysis: Common Confusions Addressed

    I have just started studying this topic and I am confused about several things. 1) Why does the assumption that D1 is reverse biased mean it is modeled as a switch? Are reverse biased diodes always modeled as a switch? 2) Also, why does the assumption that D2 is forward biased means it can...
  4. G

    Laser Diode Principles: Stimulated Emission & Voltage

    As far as I understand, when forward biased voltage applied, electrons from N diffuse to P, then recombine. Since energy gap between conductive electron and hole is const => only certain wavelength photons is emitted. In gaseous lasers for example you need to gain a populational inversion...
  5. L

    Tunnel diode via dopant concentration

    Hi, all i am confusing about the characteristics of tunnel diode if the dopant concentration increased, how change the turn-on voltage ? does it depend on concentration ? if it depends on concentration, does the turn-on voltage increase when the dopant concentration increased ?
  6. B

    Hi-pot test of a circuit with a diode

    We manufacture crank case heaters and they are designed with an 800V 1A STD Recovery diode. We do not Hi-pot the heater with the diode in it we only test to make sure we have an ohm reading in one direction and an OL in the other. However, our customer installs our heater into a system and...
  7. M

    Understand PN Junction Diode: Diffusion & Electrons

    If p-type semiconductor and n-type semiconductor of a diode are equally doped, and if the diode is forward biased, then holes will move toward the n-type semiconductor and electrons will move toward the p-type semiconductor and they will diffuse with each other and the ions become neutral atoms...
  8. E

    Flyback diode on solenoid slows solenoid retract time

    Hello, I'm an electrical engineer dipping my foot into solenoids as part of a project here at work.To monitor the position of the solenoid's armature I have a linear pot installed. My is issue revolves around a flyback diode installed across a DC solenoid I am testing. I am low side switching...
  9. T

    Basic Diode Analysis Homework: Qs on V Drop & Forward Voltage

    Homework Statement First question, In the picture attached (One diode and Resistor), when you are calculating V, is the V drop across the diode or the resistor? Second Question, In the second picture (circuit with current source) Why is the nodal analysis equation, 1A=V/100ohms +...
  10. Saitama

    How Should a Diode Be Connected in an Ammeter to Detect Small AC Currents?

    Homework Statement A moving coil ammeter is to be adapted to detect small alternating currents. Which of the diagrams shows how a diode could be connected in order to make the conversion ? (Options shown in attachment) (Ans: (3)) Homework Equations The Attempt at a Solution I...
  11. D

    Semiconductor diode (graph quesiton)

    Homework Statement The current-voltage characteristic curve of a semiconductor diode as a function of temperature T is given by the equation: ##I = I_0(e^{|e|\Delta V / k_BT}-1)## where e is the base of the natural logarithm. |e| is the charge of an electron k_B is the boltzmann's...
  12. S

    Why does diode breakdown into conduction when reverse biased?

    why does diode breakdown into conduction when reverse biased?
  13. S

    Silicon Junction Diode: Charge Density and Potential Analysis

    Homework Statement In a silicon junction diode, the region of the planar junction between n-type and p-type semiconductors can be approximately represented as two adjoining slabs of charge, one negative and one positive. Away from the junction, outside these charge layers, the potential...
  14. Saitama

    Why Do Different Paths in a Diode Circuit Show Different Voltages?

    Homework Statement Determine ##V_0## and ##I## for the network shown in attachment 1. Homework Equations The Attempt at a Solution I can replace Si diode with a battery of emf of 0.7 V and Ge diode with that of 0.3 V. If I take Path-1 (orange) in attachment 2, I get...
  15. JasonHathaway

    Diode circuit analysis textbook

    Hi everyone, My subject basically revolves around diodes circuits and how to analyze them (AC, DC). What textbook do you recommend? (If there's one with many solved problems, that would be great.)
  16. E

    Engineering Multiple diode circuit analysis

    It is well known that in order to solve diode circuits we must assume state of diodes, replace diodes with appropriate model (0.7V voltage drop) and solve circuit. Then we check result and if it agrees with initial assumption, we successfully solved our circuit. If we mark number of diodes in...
  17. V

    Solving the Diode Puzzle: Finding V with Diodes

    Homework Statement Hi so I have a problem that I don't exactly know how to approach, here's the diagram: http://images.fr1ckfr4ck.fastmail.fm/probA.jpg The diodes are supposed to have saturation current I_s = 10^(-15) A Homework Equations What is V? The Attempt at a Solution First I tried...
  18. T

    Why is my solution for real diode analysis wrong?

    Homework Statement Homework Equations I=Ise(V/VT) The Attempt at a Solution The solution I got is wrong. Does anyone know why? Here is my attempt, the image was too large for this forum so here is the link: http://i.imgur.com/4tuGxdO.jpg
  19. T

    What is the voltage drop across a diode when it's on?

    Homework Statement Find V and I in the following diagram: The Attempt at a Solution I know what the answer is. Diode D2 is off but why? Now if the voltage left of D2 was +4V then diode D2 is off because +4V dominates +3V so the current runs right and thus turns off D2. Is this...
  20. M

    Question about simple schottky diode mixers

    I am new to mixer circuit design, but I need to build a simple mixer that will downconvert a 10 GHz signal to a DC to 3 kHz signal. I know I can do this with a schottky diode and lowpass filter to isolate the lower harmonic (f-IF = f-RF - f-LO). The problem is that the RF signal will be in the...
  21. R

    Band Diagram of Multi-Quantum Well Laser Diode

    Homework Statement This isn't for a homework problem per say, though it is a coursework question. I'm writing a lab report on Multi-Quantum Well Laser Diodes and am trying to explain the basic semiconductor physics behind it. As such I need a diagram of the band structure. Homework...
  22. J

    10 Watt Solar To Car Battery With Diode

    I have an 800 amp car battery no load connected at anytime to a 10 watt solar panel with just a regular diode in between after 4 or 5 hours in the sun terminal voltage reads 16 volts is this good? Would a battery connected this way last longer than one that sits idle uncharged for 6 months? John
  23. bibo_dvd

    A problem with diode limitters

    hello guys while studing the diode limitters i found two examples i solved the first one but i couldn't with the second 1 - 2- in the first i know that the diode while be forward biased in the negative half of the signal so the negative half will be limitted to -0.7 v...
  24. P

    How to find barrier potential of pn junction diode

    I want to know that when a pn junction diode is formed and barrier potential is setup then how can we determine the same theoretically. Also I wan to know that is there any relation between barrier potential and energy band gapSmall band gap small barrier? ?
  25. H

    Exploring the Effects of High Forward Bias on a P-N Junction Diode

    What would happen if forward bias in a P-N junction were more than built-in potential? Could we reach to this situation practically?
  26. R

    Simple diode test doesn't jive. What gives?

    Probably a stupid question but I'm not sure what to search for at this point. I'm trying to do a very simple diode test (half wave rectification I suppose it's called) using an ac source. The source is a 440hz signal off of my computer soundcard (generated and played via a .wave file). It's a...
  27. D

    How to compensate for voltage drop across a diode?

    Hi, I am working on a project where I am using a LCD voltage display to measure voltage at 2 points in the circuit. The first is the voltage of the batteries providing the power, and the second is to measure the output of the circuit. It is in a very small box and I don't have room for a...
  28. ShreyasR

    Dependance of cut-in voltage of diode on scale of VI plot

    I have performed a small experiment to obtain the VI characteristics of a semiconductor diode using ANALOG DISCOVERY circuit design kit. I have connected the arbitrary waveform generator (function generator) to a series combination of a 1N4007 diode and a 1 kilo ohm resistor. To obtain the...
  29. R

    Engineering Diode logic doubt (digital circuit)

    Hello guys, I'm not getting the output of the diode logic circuits: http://upload.wikimedia.org/wikipedia/commons/1/1f/Diode-OR2.png If both inputs are 1, then there is current across the diodes then the output is 1, but shouldn't it drop because of the resistor R? If both inputs are...
  30. A

    Solve Junction Diode Problem: V & I2 for D2=10xD1 Area

    Homework Statement If the circuit shown, D2= 10 times the junction area of D1. What value of V results? To obtain V=50mV, what current I2 is needed? Homework Equations i(D)=Is(eVD/VT-1)The Attempt at a Solution I know junction area is related to diode current, so D2 has 10 times current as...
  31. A

    Solve a Diode Problem: Voltage Sources, VDD, Part A

    Homework Statement The Attempt at a Solution I know this might seem like a stupid question but are the 10/-20V voltage sources like the 5.3V or are they VDD (which is something different?) I'm also stuck on part a. If D2 is off, that means its not conducting, so zero current, but would there...
  32. A

    Voltage Across Diode Pair: Ideal Source | Vin Positive Half

    I am reading an old thread and because it is too old I can't post reply. Here is the link: https://www.physicsforums.com/showthread.php?t=449044 I want to ask about the bold part. In the case, what is the voltage across the diode pair, zero or voltage source (Vin) when it is in positive half?
  33. D

    Solve Basic Diode Problem: Will iB Always Be 0?

    Homework Statement v1 is a sine wave with amplitude ±10V and the diodes are ideal. Vo is 3V. My question is: will iB always 0? The Attempt at a Solution D1 will only be shorted when v1 < 0, which means that the voltage at Va would be from 0 to -10V and D2 would act as an open. Is that...
  34. ShreyasR

    Engineering Circuit analysis consisting of an ideal diode.

    Homework Statement Find the voltage Vo for the following circuit. Consider the diodes to be ideal. Homework Equations When a diode is forward biased, Diode resistance = 0Ω (Short circuited) When a diode is reverse biased, Diode resistance is infinite (Open circuit) Ohm's Law: V...
  35. S

    Understanding Flyback Diode Utilization in L293 H Bridge IC

    So in an application like this: The coil of the motor will, by Lenz's Law, induce a very large negative voltage across its terminals. Would this voltage be very negative at the left terminal of the inductor and very positive at the right? In this way the diode will conduct, but the negative...
  36. 4

    Best Antenna and Rectifier Diode

    What must I do to maximize the voltage received from an antenna? Also, what kind of rectifier diode has the lowest voltage cut?
  37. M

    What is the energy conversion in a forward biased silicon diode?

    A typical silicon diode has potential difference of 0.7V when forward biased, to what kind of energy is the (0.7V)*(I)*(\Deltat) converted? thermal energy only? isn't there potential energy through the electric field in the pn junction?
  38. ShreyasR

    Why does a zener diode sustain high reverse current?

    I have read that a zener diode is just a heavily doped diode. And it conducts without burn out in its breakdown region while reverse biased at its zener voltage. But why does the zener diode sustain high reverse current just because it is heavily doped? Any help is appreciated. Thank you!
  39. E

    Questions about npn transistor and operating point of diode

    For question 1, it asks me to find the operating point by different methods. But I have no idea to solve it. Can anyone give some hints for me? I can just think about the diode can be replaced by an ideal diode, a 0.5V dc source and a 0.2/4=0.05Ω resistor. For question 3, I have solved...
  40. R

    Oscillatory circuit with diode

    The LC circuit should oscillate with its natural frequency in absence of any external agent and the energy is alternatively converted from electrical to magnetic.Suppose that i include a diode in this circuit that acts as a switch.Now the capacitor is completely discharged while diode in on...
  41. E

    Explaining the physical operation of semiconductor diode (pn junction)

    what is it ? please explaining the physical operation of semiconductor diode (pn junction).
  42. P

    Calculate I1, V Drop R1, V Drop R2, I2 for Circuit w/Diode

    I attached the circuit. I need to find I_1, Voltage drop across R1, voltage drop across R2, and I_2. We're assuming the diode is 'not' ideal. Vin=5V. R1=R2=1kohm R3=2kohm voltage across R2=Vin=5V I2=5/1kohm=5mA The real diode drops about 0.7 V. So using voltage divider gives...
  43. P

    How to Determine Vd in an OP AMP Circuit with Diode?

    I have attached the circuit of interest. The question is to find Vd (drop across diode as shown in the attached image). Sorry about the handwriting on there (those can be ignored). The answer was given to be Vd=-5V. I can't figure out how they got that answer. I don't feel there is...
  44. H

    What Causes the Transient Nature of Diodes in Semiconductor Junctions?

    A pn junction diode is driven by a voltage +E to -E volts preodically when voltage is +E its forward biases and vice versa. when in forward biased a current I flows through it, now if voltage is reversed to -E, current is still I (in reverse direction). This then stay constant for a time...
  45. F

    Diode and doping on N and P regions

    Dear forum, in a diode semiconductor, the N region is rich in electrons. The P region is rich in holes. Is the number of extra electrons in the N region equal, larger or smaller than the number of holes in the P region? If so, why? Also, in the N region, it is said that the majority...
  46. A

    Maintaining Voltage Stability with a Zener Diode

    How do Zener diode keep voltage constant if input voltage is less than Zener voltage
  47. N

    I want to design a diode circuit

    i want to design a diode circuit where the Vo vs. Vi looks like this: Vi between -2 and 2 Vo = Vi Vi between 2 and 4 Vo is a linear with slope 0.5 Vi between -2 and -4 Vo is a linear with slope 0.5 Vi>4 Vo=3 Vi<4 Vo=-3 how can i do this?
  48. B

    P-N Junction Diode - Charge question

    We have been looking at P-N junction diodes in our lab session this week and investigating the current through the circuit and how this relates to the Voltage. We are using the approximation: I = (I0)*exp(qV/kT) We measured the voltage and the current for a few different voltages and this...
  49. dexterdev

    Can anyone explain me the 4 diode Balanced modulator circuit

    Hi, Can anyone explain me the working of 4 diode DSBSC Balanced modulator circuit. ie how multiplication occurs when switching. The image is attached. -Devanand T
  50. D

    Zenner Diode Clipper: AC Voltage Spikes to 22V?

    HI. I am using Piezo Electric as a AC voltage source which gives voltage spikes of around 35V little current because the impedance of the material is verry high, I would like to clip this voltage to 22 Volts i have seen that a 2 x 22V zenner diodes can be used back to back is thie right or...
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