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. Muhammad Usman

    Why is Diode reverse saturation current I_s still in the V-I equation when when a diode is forward biased?

    Hi all, This is not homework help or something, it is my general query. I read that ideal diode equation is given as in above equation Is is the reverse saturation current or dark saturation current (According to this website). And according to most of the study which I did this reverse...
  2. E

    I have a question about diodes and the PN junction

    Is the PN junction inside a diode what makes the electrical current only flow in one direction and not in the opposite direction? If this is so, why does it happen? Also Why is the P-type material said to have empty holes and the N-type material to have free electrons?
  3. Edy56

    Engineering Power dissipation of 2 diodes (1 is a Zener diode)

    Are my equations correct? And my process of how I should solved this problem?
  4. ARoyC

    Engineering Optimizing Diode Performance: Load Line Analysis

    I have drawn the I-V characteristic graph of the diode. I am facing problems with drawing the load line. For what value of E (Source Voltage), should I draw the Load Line? To get the I-V graph, I had to continuously change E.
  5. S

    Experiment about diode related to temperature and potential difference

    (a) I know some of the apparatus needed for the experiment, such as DC power supply, ammeter, voltmeter, maybe rheostat. But I don't know how to change the temperature of diode. What is the correct and safe way to change the temperature of diode? Thanks
  6. P

    Help needed with Varactor diode test circuit

    In the circuit simulator there is no voltage at the Varactor cathodes when Vbias is zero, but depending on the Varactor I use on the breadboard it can be as high as 7.4 volts! There is minimal current through the series resistor when Vbias is applied in LTSPICE, but I always see a significant...
  7. bmihalik

    I Using Lenses with Laser Diode Microscope to Reduce Aberrations

    I would like to build a microscope witch can be used with different monochromatic light sources (laser diodes), and this system should has small astigmatic and coma aberration, but keep the chromatic aberration property. Can I use two spherical or ashperical lenses (facing with convex side to...
  8. Raihan amin

    Understanding a heat sensor circuit?

    What I understand is that the β parameter of the npn transistor is temperature dependent. Increasing the temperature increases the collector current and hence the LED turns ON. But I don't understand the resistor arrangement.Also I can see that the diode is keeping the Base-Emitter junction in...
  9. Aymangh994

    According to which criteria should I choose a laser diode?

    Hello everyone, I don't know which laserdiode and lens system should I choose for my Project. It is all about AFM Microscopy with a cantilever ( Length= 450 um, width = 50 um and thickness= 2um). So as you see it is not a small cantilever. As far as I Know, the larger the cantilever is, a larger...
  10. N

    Using delicate 5V IC to toggle 12V device with MOSFET, Diode, resistor

    Hey all, I have a 5v IC that is triggered by a sensor to unlock the 12v lock, I am using a NPN transistor as a switch with the 5v VCC as the gate, I need it to sink back to the GND of the IC without blowing it, is this safe? If not what changes would you suggest, it has been years since I've had...
  11. N

    Two basic diode and capacitor circuits

    Hi there! I have resolve this basic circuit, but, i have a little questions about. The first circuit its: The diode in all voltaje cases act like a switch, so, the courrent of all components and voltage of the resistance its zero. I graph the curve according my interpretation. My question its...
  12. S

    Graph of waveform across diode shown by CRO

    Option (A) and (B) is wrong because the waveform should be half-wave, not full-wave. But how to know whether it will be (C) or (D) based on the circuit given? Thanks
  13. Stonestreecty

    Troubleshooting Laser Diode Circuit with Arduino and PN2222a Transistor

    Hi, all I have a circuit where the base transistor (PN2222a) leg is plugged into the pin 9 of the Arduino. When I power everything up and send the signal from the Arduino to the transistor base leg, the laser diode doesn’t light up, but my design strictly follows Complete Tech Guide to Laser...
  14. G

    Can RF101 Diodes Be Used in Low-Frequency Recovery Circuits?

    Hello! This is my first post. Problem to use RF101 Diode: There is little RF 101 diode that I can search for. And I have a project about the recovery circuit. but the frequency of the rectifier circuit is very low, it only has requirements for the withstand voltage. As long as the withstand...
  15. rkgjet

    Space charge region of p-n junction diode

    does np=ni^2 holds even the space charge region of a pn junction diode?
  16. P

    Understanding diode (LED) resistance at V=0

    I'm working with some bare chip diodes for an application where I need extreme luminosity. These are the diodes here: https://www.irtronix.com/leuv-v625a6 I notice that some of the diodes have very significant resistance (on the order of megaohms) from anode to cathode and some have very small...
  17. cheniour oussama

    Simulate Leakage Current - Reverse Bias Diode

    hello I m Trying to simulate leakage current, say from a reverse bias diode I'm fairly how i can do it
  18. Andrei0408

    Calculate the voltage across a resistor using Thevenin's Theorem

    I'm thinking I should apply Thevenin's Theorem to find the voltage, but I need to find I_D in order to be able to calculate U_S.
  19. Andrei0408

    How to find the voltage threshold at which diode switches states?

    I've attached pictures with the circuit and part of the attempted solution. I've replaced the diode with its offset model and obtained the equivalent circuit in the 2nd picture. After applying KVL, I've obtained that u_l=−u_D−i_D*R. Since U_D0 is greater than 0, I've deduced that the diode must...
  20. willDavidson

    Understanding PV Cell Modeling: Single vs Double Diode

    I am looking at modeling a PV cell and I'm trying to understand the real difference between the single diode and double diode mode. I now realize that I don't fully understand the purpose of the diode in the model in the first place. I've just learned that it was there and went with it. I...
  21. W

    Diode Power Calculation: Understanding the Basics

    Hello all, I've just started learning about diodes.. I believe I've done this problem correctly (question in black), although want to make certain I'm understanding the very basics before moving on. Thank you
  22. sophiecentaur

    What type of diode is best for protecting batteries in a weather station?

    It's a mod to a weather station which normally uses primary cells alone. There are four cells, connected as 2X2. I am providing dc power up there for another purpose so I thought it may as well supply the station as well. But I need to protect / isolate the batteries from the DC source with a...
  23. OwlsInATrenchcoat

    B Logarithmic IV graphs of diodes

    Hello there, I've been working through a task (that doesn't have an answer sheet or explanation) in which we plot I against V for three different diodes. Each has a different threshold voltage and displays the usual charcteristic curve. The final question is this: "It is suggested that the...
  24. T

    Problem with this Laser diode circuit

    I have dismantled an old DVDRW drive and taken a 4-pin laser diode from it. After connecting it to two 2A batteries (red with positive, and blue with negative), the light beam is diverging, and the brightness is even dimmer than another laser diode that I got from a presentation pen. Also...
  25. D

    Semiconductor (Diode) Lasers and Properties

    print ('Calculate threshold, power, slope efficiency for different lengths of SC Laser') g = 510 # The gain of the laser, arbitrary value of 510 m^-1 was picked I = np.linspace(0, 0.03,5) #DRIVE CURRENT; 100 values of current, 'I', between 0A and 0.03AV = 1.8 #INPUT VOLTAGE; arbitrary value of...
  26. B

    Finding the potential difference of a diode

    I've tried doing it but i haven't been able to find the resistance of the diode.
  27. T

    Fundamentals of the PN Junction

    Unbiased circuit (no driving voltage source) ************** Fig 1 The N-type material has a tendency to donate electrons to the P-type (i.e. absorb holes from) across the PN junction via diffusion current exclusively within the conduction band of both materials. It does so after those...
  28. DaveE

    Why do people refer to the "fast axis" vs. "slow axis" of Diode Lasers?

    This is really a nomenclature question. The radiation pattern of a typical laser diode has one axis with low divergence (the slow axis) compared to the other (the fast axis). I understand about antenna radiation patterns, spatial Fourier transforms (Fourier optics), etc. So I think I understand...
  29. Praveen1901

    B What is the purpose of the depletion region in P-N junction semiconductors?

    I'm new to semiconductors. While I was studying types of biasing in semiconductors, here's what I read - 'In forward biasing, the width of the depletion region is reduced.' Here's what I thought - Since the potential barrier is reduced in the junction due to external potential, the diffusion...
  30. J

    Engineering DC bias current and small-signal resistance

    We are given that ##i_D = 8\cdot 10^{-12} (e^{v_D/20m} - 1)## Hence ##i_D' = e^{50 v_D}/2500000000## and ##i_D'' = e^{50 v_D}/50000000## Then I have that ##\delta i_D \approx\frac{ e^{50 v_D}}{2500000000} \cdot \delta v_D = \delta v_D / 5## Cancelling ##\delta v_D## from boh sides and solving...
  31. D

    Diode passing voltage in both directions.

    i connected a diode to a 4 volt battery. in 1 direction the diode passes 4 volts. in the other direction the diode passes 1.9 volts. is this normal? shouldn't the diode pass 0 volts in the other direction?
  32. Sid55

    Schottky diode with the correct voltage and current rating

    Non-isolated boost converter Input Voltage: DC8.5V to 50V Output Voltage: DC10V to 60V Max. Ouput Current: 12A Frequency: 150KHz
  33. M

    Engineering Calculating Voltage Drop Across Non-Ideal Diodes

    So I have this circuit up above and I need to find the voltages across each of the diodes. The only info given is that they are identical silicon diodes at T = 300K. My first thought was that since the diodes are opposite, D2 would be in reverse bias and would act as an open. However, I realized...
  34. D

    I am confused -- how to bias the diode in a boost converter?

    i have been researching how to build a boost converter. according to the articles i have read, when the switch is closed current flows through the switch to the negative terminal. when the switch is opened, the back emf from the inductor and input voltage add, which forward biases the diode. i...
  35. J

    How does applying potential affect the energy band diagram for a diode?

    Ref: http://hyperphysics.phy-astr.gsu.edu/hbase/Solids/pnjun2.html Hyperphysics Asstr Why does the band diagram shift up or down when I apply potential? Why does it shift down when positive potential is applied? Professor said it's because electron has negative charge and so we consider...
  36. wirefree

    Engineering Diode circuit with a Capacitor

    Summary: Seek help with the working of a Capacitor in the presence of a DC & AC voltage source. I greatly appreciate this opportunity to submit a question. It's a homework problem and I only seek to clear my concepts. Problem: Find amplitude of the ripple voltage across the resistor...
  37. Ramazan Duzgun

    What is the design methodology of a Heatsink for a high-power diode?

    In reference of Ned Mohan's book, I have designed a heatsink, firstly natural convection taken into account, but laboratory test results and theoretical calculations are not matching. The test results: For 40 A (means 62 W), 30 Celsius ambient temp, it raised up 51 Celsius. So, Rs-a =...
  38. shushi

    Novice question about Relays, Capacitors, and Diodes

    Hello, In regards to this relay, TQ2SA-1.5V Panasonic 2 Form C AS Single side stable, 1.5VDC 2A DPDT NON-LATCHING SMD Relay https://www.mouser.com/ProductDetail/769-TQ2SA-1.5V PDF 1 of Relay PDF 2 of Relay (specifically pages 5-6) is attached at the bottom as a pdf file. I was previously told...
  39. C

    A Is there a passive molecular flow 'diode'?

    During high vacuum pumping, one sucks viscous gas out of a chamber down to just above the molecular flow density where viscous flow becomes absent, and then may employ a different sort of pump to start pulling in the remaining molecules: Molecular flow. I have been wondering for a while if...
  40. T

    Using a generator to charge 2 batteries

    My project is to create a circuit for a stroller that can store the mechanical work into electrical while moving around and with the push of a switch, use the electrically stored energy to assist the movement of the stroller. I’ve tried capacitors but it ended up not being enough voltage and I...
  41. C

    Is Ohmic Resistance Applicable to Diodes?

    Well I was just wondering how ohmic resistance works in a diode . I mean let's take forward bias mode.In forward bias mode electrons are diffused from the n type region to the p type region.The depletion layer still exists but is very narrow.So according to Drude model of ohmic resistance...
  42. C

    B What Happens When We Apply a 10V Source to a Diode in Reverse Bias?

    Assume we have a diode . We connenct the negative terminal of the battery(anode) to the n type region and we connect the positive terminal of the battery to the p type region of the battery.The net force forces electrons to start flowing from the n type region to the p type region.As long as we...
  43. C

    Semiconductor physics: Voltage below forward voltage

    Assume we have a diode closed circuit.We connect the p type region of the diode to the positive terminal of the battery(cathode).We connect the n type region of the diode to the negative terminal of the battery(anode).The voltage of the battery is 0.3V .The diode%s intristic se miconductor is...
  44. C

    Diode operation from reverse bias to zero bias

    Assume we have a closed diode circuit .We connect the n type region of the diode to the positive terminal of the battery.We connect the p type region of the diode to the negative terminal of the battery.The depletion layer is increased.Now we open the circuit.Why the diode returns to its zero...
  45. archaic

    Load resistance in voltage regulator

    Homework Statement [/B] I want to find the minimum resistance ##R_L## so as to maintain ##V_z##(voltage of the zener corresponding to the minimum current ##I_{z_0}##) across the same resistor ##R_L##. Homework Equations ##V_z##(voltage of the zener corresponding to the minimum current...
  46. Abimbola1987

    Measurement of vacuum diode electron flow

    Dear Sirs, After my theoretical post on vacuum diode electron flow, I decided to try and measure it physically. I didn't have a vacuum tube, so I improvised with some tungsten wire, aluminum sheets and some screws and the result was usable. Obviously the tungsten wire fails after some time due...
  47. Abimbola1987

    Understanding Electron Flow in Vacuum Diodes

    Dear Sirs I have been going through the "radiotron designers handbook", but I can't seem to find the answer to the doubt I have about the electron flow of the source Vp. Kindly consider the below two circuits, the difference is the polarity of Vf. Question: In both circuits, the electrons...
  48. Boltzman Oscillation

    Engineering What is the output voltage of this ideal diode circuit?

    Homework Statement Given the following circuit: what is the positive and negative peak values of Vo? vi has a frequency of 1kHz, peak of 5V, and is a sine wave. Homework Equations x(t) = Vsin(2(pi)*f*t) KCL, KVL, etc. The Attempt at a Solution [/B] I made Vi to be 5sin(2(pi)1000t) during...