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Questions tagged [pn-junction]

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13 views

Carrier concentration of pn junction in reverse bias

I'm trying to understand the effect of forward and reverse bias in the carrier concentration of a pn junction. I know that in equilibrium the first picture below holds. When we apply forward bias, the ...
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24 views

Short N region diode

A diode was manufactured by making an abrupt junction between a region of length \$W_p\$ having a concentration \$Na = 10 ^ {18} cm^{-3}\$ and a region \$ W_n\$ with \$Nd = 5.10 ^ {15} cm^{-3}\$ of ...
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1answer
36 views

Diode lifetime VS junction temperature

I have one bridge rectifier operating at the constant junction temperature of ~72°C, (GBPC3510W datasheet), which is rising to ~80°C in some specific cases. I'm trying to find a kind of "aging curve" ...
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3answers
87 views

Total current current equation in P-N junction

So Okay I get why there is a negative sign in the equation for diffusion current of holes since the gradience is actually negative if we put our coordinate axis in the bottom left corner for example ...
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1answer
60 views

Given a diode circuit and some of its values, how do I find the temperature?

Let's say I am given the following circuit: along with $$dV_p/dT=0.139mV/K$$: Defining V1 the voltage above Diode D1 and V2 the voltage above diode D2 , we use the expression for the current of a ...
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2answers
176 views

Deviation from typical I-V characteristics of a diode in high frequency

Why the diode shows a loop in the I_V characteristics?(Diode part N4003, Frequency was 100k) My instructor told me something regrading the retardation of charge carriers but I couldn't understand/find ...
2
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1answer
90 views

How do LEDs stay on constantly?

In a LED (light emitting diode,) a forward bias allows electrons to fill the vacancies in the p-type region, recombining with holes to emit a certain frequency of light. After a set amount of ...
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2answers
60 views

Confusion regarding Common-Emitter configuration of a BJT

This is a picture of a Common-Emitter Configuration of an n-p-n BJT, taken from a book :- For the BJT to be in active mode, the Base-Emitter junction should be forward biased, and the Collector-Base ...
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1answer
56 views

Photodiodes: the “generation” mechanism behind photocurrent

Assume I use a photodiode under zero-bias (that is in photovoltaic mode). How/why can a current flow in this bias condition? As far as I have understood the working principle of photodiodes, when ...
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33 views

Calculating Nmax in loaded bipolar junction transistor inverter

I have tried various methods for calculating N max here, and some have resulted in negative answers while others have resulted in an answer of around 1. Is my method correct? Or am I missing ...
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2answers
83 views

P-N Diodes in series. Is my solution correct?

I have attempted to work out a solution on a short question relating to p-n diodes. Is my solution correct? The question (from a past paper) : From the question I understand that there are two ...
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2answers
60 views

Forward Bias PN Junction

The depletion region is formed at the junction due to diffusion which creates a thin width of negative ions on the p side and positive ions on the n side whose electric field restricts further ...
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14 views

Linearly graded and step graded PN Junction represent uniform or non-uniform doping?

Linearly graded and step graded PN Junction represent: a) Non-Uniform Doping , Uniform Doping b) Uniform Doping , Non-Uniform Doping c) Uniform Doping , Uniform Doping d) Non-Uniform Doping , ...
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2answers
54 views

What bias voltage is applied to a PIN photodiode when connected only to multimeter

If I take just a PIN photodiode (e.g. BPW34 FAS ) and connect a multimeter to its terminals to measure current, for example: expose the photodiode to the sunlight and read current of ~1 mA on the ...
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1answer
48 views

Barrier voltage and temperature of a PN junction

Why does the barrier voltage of a PN junction decrease by increasing temperature ? Please if possible , i want to understand the inner physics of what happens
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3answers
109 views

BJT Active mode - How does it work

I am finding it difficult to understand how exactly this works and would appreciate any help. From my understanding: The emitter base junction has to be in forward bias meaning that Vb is more ...
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2answers
147 views

Find cause of diode destruction from destroyed diode itself

Is it possible to find the cause of power diode destruction, ie. if it was destroyed through: reverse overvoltage spike (reverse breakdown and subsequent thermal destruction due to reverse ...
2
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1answer
102 views

Estimate temperature for silicon (p-n junction)

I need to estimate the temperature at which p-n junction made of silicon lose it rectifying characteristics. (\$N_A=N_D=10^{15}\,cm^{-3}\$) \$E_G\$ is independent of the temperature and are 1.12 eV ...
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44 views

Diodes when voltage is applied

Does the hole injection take place from p semiconductor to n semiconductor in a pn junction diode? Or it takes place only in the case of a transistor?
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1answer
72 views

Thermal drift in diodes

Hi guys and thanks for reading and your help. I can't understand a thing that my book says: "When the temperature grows, the diode will let flow more current" and then it gives 2 formulas: \$V_t = \...
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1answer
555 views

Drift current in PN Junction

Ok guys, first of all thanks for your support and your help, I can't understand how the drift current work, let's say that we have this junction By the definition of the drift current we can ...
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3answers
189 views

Why not all the diodes are in “on state” in the given picture?

Given:"all the diodes are ideal",in figure (e), only D3 is on and rest of the two diodes are given off in the solution. Similarly for (f) only D1 is on. I don't understand the logic behind this. ...
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2answers
106 views

Measuring junction temperature of LED tape?

My boss at work wants me to figure out a method of measuring the junction temperature of an LED that is part of a reel of tape. Unfortunately, there is no datasheet for the LED modules themselves, ...
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1answer
36 views

pn junction in series i-v curve

If i have \$p^+n -pn^+\$ junctions in series how should the i-v curve look? my guess is that because they have the same orientation in the meaning of forward/reverse bias so it's should look like ...
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2answers
2k views

What the difference between pin and pn diodes i-v curve?

For my understanding there should be no big difference in i-v curve between regular p-n junction and p-i-n junction, the only difference i can think about is do to the bigger resistance of the ...
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2answers
77 views

When Pin diode is no longer junction?

For p-i-n junction with intrinsic region d, I need to answer what happens when d is very large. So from simple logic, I believe that at some point there will be no diffusion of charge carriers from p-...
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3answers
402 views

Is the following information about the diode reverse breakdown voltage correct?

Regarding the PN junction diode, is the following information correct?: How come the reverse breakdown voltage increases with temperature according to the above graph? Am I interpreting the plots ...
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2answers
2k views

Electric field and potential plots across a pn junction diode

Below shows how the charge density, electric field and potential is varying along the horizontal axis of a pn junction diode under equilibrium: I can understand the the charge density plot easily ...
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2answers
129 views

Can a reverse biased diode be driven past its voltage rating but with current limited to few uA

If, for example, a Silicon diode rated at 100V is reverse biased at 200V (long term, not just very briefly) but in series with a few MegaOhm resistor such that the reverse current is limited to one ...
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1answer
482 views

For p-n junction, at the depletion region which side is at higher potential?

At depletion region, a potential barrier is setup, E(electric field is from right to left)[according to viewer], but left side is shown to be at higher potential. Inside a battery, E is in the ...
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1answer
7k views

What is a typical diode's ideality factor?

Some background, for anyone unfamiliar: The Shockley diode equation is \$I_D=I_S·(e^{\frac{V_D}{n·V_T}}-1)\$ with the quantity \$n\$ called the ideality factor, a number between 1 and 2. Ideal ...
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1answer
53 views

Above the barrier voltage does a pn junction behave ohmically?

I understand that below the barrier voltage no current flows, and once the required voltage is met the current rises exponentially, in accordance with the ideal diode equation. However at voltages ...
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2answers
1k views

Why does the depletion region penetrate more into the lightly doped region in a pn junction?

I have read at several places if we take exact same cubes of p and and n doped semiconductor material and form a junction, the depletion region(blue colored region in my drawing) will be asymmetric ...
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1answer
793 views

Relation between junction and capacitance and reverse bias voltage [closed]

Can someone explain how junction capacitance in reverse bias voltage depends on the rate of change of external diode voltage(vD)? I tried to find the answer on google but was not successful.
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1answer
780 views

Diode voltage dependence on temperature

Question: In the circuit D1 is a large-area, high-current diode whose reverse leakage is independent of applied voltage, while D2 is a much smaller, lower-current diode for which n = 1. At an ambient ...
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1answer
100 views

Why two seperataly doped semiconductors cannot be joined to form a junction? [duplicate]

My textbook says that when a slab of P-type semiconductor and another slab of N-type semiconductor are joined, they cannot form a junction because no matter however smooth the surface is, there will ...
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2answers
114 views

Diode Circuits using expotential model

simulate this circuit – Schematic created using CircuitLab Hi, Question: In the following, a string of three diodes is used to provide a constant voltage of about 2.1 V. We want to calculate ...
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1answer
373 views

Diode Modelling

simulate this circuit – Schematic created using CircuitLab Hi, Question: In the following, a string of three diodes is used to provide a constant voltage of about 2.1 V. We want to calculate ...
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1answer
679 views

Drift current and reverse saturation current

I have a few questions whose answers I couldn't find. All questions are in respect to a pn junction diode. 1) Does diffusion flow of current (even minimal/negligible) occur at reverse bias? 2) If ...
3
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2answers
3k views

Dynamic resistance of a p-n junction diode

The slope of the graph between current and voltage in a p-n junction diode, under both forward bias and under reverse bias, varies a lot on varying the voltage. Hence, given the graph, how do we ...
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4answers
471 views

What happened to Depletion region when biasing is Off after applying reverse biasing?

I was studying Diodes and I came across the information that when the diode is reversed biased the depletion region is increased. Now the depletion region is composed of neutral atoms that are ...
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2answers
101 views

Diode breakdown

I read in the book, "Microelectronic Circuits" that the breakdown of a pn junction is not a destructive phenomenon given that the breakdown current is limited to a safe value by an external circuit. ...
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34 views

Thin p+ side in photodiode

The diagram of the photodiode is shown below. Why is the p+ layer very thin here? Could we have used a n+p configuration instead?
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2answers
470 views

Constant voltage-drop diode model?

I'm in the process of learning about diodes and I'm currently learning about diode models. I came across the model called the constant voltage-drop diode model. So, let's say the diode built-in ...
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3answers
308 views

When would I not want to replace a PN diode with a Schottky diode

When repairing or maintaining equipment, or even during design revisions, why would I, for electrical reasons (not interested in the potential financial aspects) not want to replace a PN junction with ...
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2answers
106 views

Why current is constant during storage phase in reverse recovery experiment?

This is a simple schematic of reverse recovery experiment. As you can see, there is a constant current phase in the curve known as storage phase. My question is, why current is constant during ...
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2answers
93 views

Do photons come out when electrons and holes recombine inside a forward biased diode?

When electrons fall to a lower level orbital they emit light/radiation at a particular frequency. Is that the case for recombination? My question came from this speech at the following part: https://...
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1answer
589 views

why maximum value at middle of pn junction is negative?

Why the slope of the electric field of N side of the junction is positive and p side is negative.Also, why can't be maximum value be positive i.e on the Positive axis of the Electric field?Please ...
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1answer
492 views

Can I switch off a PNP transistor by forward biasing the collector-base junction, but have the base-emitter junction forward biased?

I need to switch off a PNP transistor however, the voltage on the emitter side will always be larger than the base. Is there a way to switch the transistor off? Edit: The aim is to maintain a ...
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2answers
419 views

What is the difference between builtin voltage and cutin voltage in pn diode?

I am little bit confused that how these two are different.