What is Diode circuit: Definition and 48 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. 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...
  2. 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...
  3. 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...
  4. 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...
  5. 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...
  6. 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...
  7. 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...
  8. 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...
  9. N

    Conduction Angle of a Diode Circuit

    Homework Statement I am trying to prove that the diode conducts between the expressions shown here: Homework Equations I know that Vo = Vpsin(wt) and the only information i know about the diode is it has a turn on voltage of Von. The Attempt at a Solution I have tried to plug the variables...
  10. V

    PNP Transistor voltage calculation

    For the B) part, I don't get why is it that for calculating voltage between collector an the emitter (Vce) I take into account diode on base (0.7V), whereas for part A) it's ignored? Why is Vce in part A and part B are calculated differently? Why is it that in part A voltage of 0.7V isn't taken...
  11. DakotaE

    Trying to determine the size of Diodes required

    Hey All, i just joined today to try and figure out what size of diodes i need for the project I am working on. I am working on installing a new Light Bar and Flood Lamps to my Jeep to get better light at night. This is my hope to accomplish: Relay 1 will be used to turn the LED Light Bar and...
  12. V

    Circuit with two voltage sources, finding voltage at nodes

    Okay, so why is it that Vc assumed to be 12v - 0.7v (D1), how about contribution from the 9v battery?? Why is this not affecting the voltage at node C? Why Vc isn't 9v - 0.7v (D2) = 8.3v?
  13. whatphysics

    Finding the forward current of diode

    Homework Statement A Si diode is operated at the room temperature (27 °C). For a forward current of 1 mA, the voltage VD is found to be 0.9 V. If the VD is 1 V, the forward current = _____ mA. Given that nVT = 26 mV The answer is 46.81 Homework Equations Shockley diode equation? The Attempt...
  14. 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...
  15. S

    Engineering How do I start this problem? (diode circuit)

    Homework Statement Find Vo and draw the waveform. The two diodes are silicon diodes with a voltage drop of 0.7V. Homework Equations (given by my teacher)[/B] Id = Io * (e^(qv/nkt)-1) Vp = Vrms * sqrt(2) Vrms = Vp/(sqrt(2)) The Attempt at a Solution I have no idea how to find Vo or the waveform.
  16. 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?
  17. 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...
  18. 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...
  19. 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...
  20. A

    Engineering Junction diode circuit problem

    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...
  21. 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...
  22. 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...
  23. 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.)
  24. 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...
  25. 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?
  26. L

    Graph Vout vs Vin of diode circuit

    Homework Statement [PLAIN]http://postimage.org/image/bd4pyoqkt/ Make a sketch of Vout vs Vin for Vin from 0 to 5 V, assuming that both diodes have a diode drop of 0.5 V Homework Equations None that I know of. The Attempt at a Solution The way I see it, the Vout will start at...
  27. C

    Transistor and diode circuit

    I just wanted to see if I am understanding this circuit correctly. Let's say the input voltage (V_in) is 0. This means: 1) no current through the 1000 ohm resistor 2) no 0.7V drop from the base to emitter 3) transistor is pretty much off 4) The circuit is open, thus no current goes through...
  28. T

    How to Analyse a Diode Circuit: Understanding Voltage and Current Relationships

    I'm a quite confused as to how to analysie a diode circuit How would I go about analysing the following? I know that I need to analyse the circuit with the diode on(short circuit) and off(open circuit).
  29. D

    Is This Diode Circuit Analysis Correct?

    Hello everyone. Can you tell me if i solve right this circuit? D2 is on off mode so I2 is approximately 0,D1 is the same and D3 is on ON mode so the equivalent circuit is like AFTER. Is it ok what i did? http://postimage.org/image/mblq1dr7n/
  30. E

    Engineering How to Analyze a Diode Circuit with Multiple Voltages

    Homework Statement Find voltage at Vo1 and Vo2 The left part is the schematic used in the question. The right side is the engineering schematic I drew up. The Attempt at a Solution I'm not sure what to do here. because there is a Si and Ge diode that means the Ge will be actived first...
  31. S

    Engineering Circuit Analysis of a Positive Offset Clamping Diode Circuit

    Homework Statement Plot the waveforms for capacitor voltage VC, output voltage Vo, and diode voltage Vd given that Vs is a 20 Vpp triangle wave with period T. Use CVD model with diode VON = 0.7 V. Homework Equations KVLs? The Attempt at a Solution From my basic...
  32. S

    Engineering Diode Circuit ON/OFF Model Problem

    Homework Statement Homework Equations When Diode is on Vd=0.7 V and Id=0 When Diode is off Vd<0.7 and Id>0The Attempt at a Solution I've been working on this problem for hours now but I just can't logic it out properly. I know the right model is supposed to be D1 ON and D2 OFF, but I can't...
  33. P

    Engineering Logical diode circuit description

    Homework Statement i.imgur . com/tjtAC.png (Sorry! It's fine I promise!) I was given this circuit and I need to know what exactly what kind of circuit it is. i.e. what kind of logical operation it performs. V_o is the output. IN1, 2, 3 are the inputs. I need to know the states of conduction in...
  34. S

    How to design a diode circuit?

    Homework Statement Given an input range of voltages (for example, 5-15V), design a circuit using resistors and diodes (and voltage sources) to turn on at input = 5V and turn off at input = 15V. (I chose 5 and 15 arbitrarily).Homework Equations The Attempt at a Solution I am able to get it to...
  35. C

    Engineering Quick question on diode circuit

    Homework Statement Homework Equations The Attempt at a Solution Just want to know whether I have the right idea: so to determine the reverse saturation current (IS), I just determine it for each value of VD that was given? So finding IS for 0.6, 0.65, 0.7 etc? The question...
  36. F

    Creating a Voltage Transfer Characteristic (VTC) for a Zener Diode Circuit

    http://img847.imageshack.us/img847/1922/capturevq.jpg I need help starting this. So far I am getting Voh = +10V from the zener diode, and Vol = -10V, the upper and lower saturation limits based on the zener diodes Then for threshold values I am getting an upper threshold Vth = -R1/R2 * Vol =...
  37. I

    Engineering Help with Diode Circuit with Current/Voltage through Diode

    Homework Statement For the circuit shown in Fig. 4.26 both diodes are identical. Find the value of R for which V=80mV Homework Equations I'm not quite sure what equation to use here. If you look at the wiki page on diodes http://en.wikipedia.org/wiki/Diode it might be Shockleys...
  38. F

    Engineering Solve Ideal Diode Circuit - Find V & I

    Hello, I have been given a homework problem about ideal diodes. The diagram is below. I need to find V and I. I have the solution (4 mA and 1V) however I am unsure as to why it is so. I would have set 5V at the node where the resistor and 3V diode meet therefore setting all the diodes to be...
  39. G

    Engineering Diode Circuits: Find Q-Point for D1

    Homework Statement For the figure below, use the ideal diode model and the constant voltage drop diode model (assume a turn on voltage of 0.6V) to find Q-point for diode D1: [PLAIN]http://gotejjeken.webs.com/ckt.jpg Homework Equations KCL/KVL The Attempt at a Solution For the ideal model, I...
  40. T

    Engineering Power dissipated in R (zener diode circuit)

    Homework Statement A zener diode runs off 10V and supplies 5V to a load that draws 100mA. The minumum zener current = 5mA. R = 47Ω What is the dissipation in the resistor if the output is short-circuited? Homework Equations None. The Attempt at a Solution Using R = V - Vz / Izmin...
  41. S

    Calculating Current and Voltage in a Diode Circuit

    Homework Statement I have the following circuit: [PLAIN]http://elementdesign.sk/dioda.jpg I would need to calculate the current and voltage through the diode. I now that I can calculate the current by the following formula: I=I_{0}(e^{U/U_{0}}-1) I know that I_{0}=10^{-17} and U_{0}=20mV...
  42. R

    Engineering Complex Diode Circuit: Solve DC Output, Ripple, Rating & Power

    Homework Statement Consider the following power supply circuit, which uses typical component values. The diodes have a forward drop of 0.6V each. Transformer voltages are RMS (root mean square). http://img294.imageshack.us/img294/1665/70454661.png a. Determine the DC output voltage...
  43. J

    Engineering Simple Diode Circuit Analysis: Homework Help and Solutions

    Homework Statement Attached is the homework problem I'm having difficulty with. I need to sketch vout for the circuit, assuming the diode ON voltage is 0.6 V. I'm stuck at how to begin this problem. Homework Equations The Attempt at a Solution It's only the 2nd week of class so...
  44. F

    Solving a Diode Circuit with Varying Resistances

    Homework Statement A diode with reverse saturation current of 1pA and an ideality factor of 1.15 is connected in series with a resistance of 200ohms and connected to a 5V DC supply voltage. Find the current flowing in the diode at a temperature of 290K? How does the current change when a...
  45. D

    Engineering Solve Diode Circuit Problem: Homework Equations & Attempt at Solution

    Homework Statement See attachment Homework Equations We are to assume the voltage drop across diodes is .7v (don't use the diode equation!). The Attempt at a Solution I first was assuming that both diodes were "on". Then my work is as follows: V1 is the voltage directly above diode D1 (the...
  46. A

    Another problem, voltage characteristic in a diode circuit

    Good morning lovely people ! As I got some really helpful advice here yesterday i though i'd try it again, hopefully you haven't yet had too much from me (-: So my question is concerning the attached PDF file (Last problem #3) i am asked to find the current I_B in 3a) and 3c) but to my...
  47. D

    Solving a Diode Circuit: Output Voltage & Resistor R Values

    Homework Statement A scheme of a diode circuit is attached. The voltages at the inputs A and B are 5V. A. What is the output voltage (=voltage at the black node, Z)? B. What values of resistance would you recommend for the resistor R? 2. The attempt at a solution A. The diodes D1 and...
  48. S

    Calculate Voltage Across 4k Resistor in Simple Diode Circuit

    I have an interesting question about this circuit... if I were to calculate the voltage from point X to ground... essentially all it is, is voltage across the 4 kilo-ohm resistor because if it went the route of the diode, it would lose an additional 2.7 volts.. so its going to take the better...
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