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Questions tagged [pn-junction]

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1answer
23 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
63 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
84 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
56 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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0answers
43 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
36 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 = \...
3
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1answer
118 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 ...
3
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3answers
175 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
84 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
34 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 ...
0
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1answer
860 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
74 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
168 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
657 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
117 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 ...
0
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1answer
293 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
3k 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 ...
0
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1answer
50 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 ...
1
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2answers
732 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
540 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.
0
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1answer
529 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 ...
1
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1answer
84 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 ...
3
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2answers
87 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 ...
0
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1answer
243 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 ...
0
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1answer
512 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
2k 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 ...
5
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4answers
314 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
91 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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0answers
32 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?
0
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2answers
370 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 ...
5
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3answers
211 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 ...
1
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2answers
89 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
84 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://...
1
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1answer
461 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
438 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
267 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.
-1
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1answer
434 views

if beta=infinity, what is Vo/Vbe?

So i've been given this problem and i really don't know how to approach to solve it. What i know is that if beta is infinity, then Ib1 will be zero, then ie1 and ie2 will alse be zero(if i'm right). ...
0
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1answer
292 views

Reverse recovery method for carrier lifetime measurement

I have used reverse recovery method for measurement of carrier lifetime. I have used a simple setup consisting of a function generator, a resistance and DUT (design under test). In a conventional ...
0
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3answers
213 views

How can I calculate the current through an LED? [duplicate]

I am trying to find out if increasing current increases the brightness of an LED. I'm pretty sure this is the case now that I have looked into semiconductor band theory physics and p-n junctions. ...
0
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1answer
375 views

Diode PN Junction depletion region under bias

I understood the formation of depletion region in a PN junction with no external bias applied.Immobile ions caused due to diffusion of holes and electrons causes electric field and hence the depletion ...
1
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1answer
502 views

current of forward-biased pn junction

I've been studying pn junctions from the 5th edition of Sedra & Smith's Microelectronic Circuits and I've hit a roadblock regarding how the junction works in forward bias and, more specifically, ...
0
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1answer
2k views

What are the reasons that the emitter is heavily doped in an NPN BJT? [duplicate]

Is doping the emitter more than the collector crucial? Would current not flow at all if both regions were equally doped? Why? Is there a way to explain this in a simple fashion?
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4answers
482 views

Why is barrier potential of Ideal Diode zero?

I am learning the basics of semiconductors. Going through diode equivalent circuits, the material says that Ideal Diodes have a barrier potential of 0 volts. Why is this? I have understood what a pn ...
0
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1answer
574 views

net current direction in a pn junction?

in forward bias, when the holes enter the n-region and when the electrons enter the p-region, the recombination happens and the carriers annihilate each other. so how does the net current generate? on ...
0
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1answer
104 views

Depletion region of an NMOS and insulator

I'm trying to get a better understanding of what the electrons and holes are doing when an NMOS is in the depletion region. So far I understand that the holes in the P- substrate are attracted away ...
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1answer
2k views

Current gain or voltage gain?

I know that current is amplified by junction transistor but what about voltage? Is voltage also amplified at same time as current or not? In school professor was explaining me about this and I still ...
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1answer
196 views

Pn junction under forward bias

If two batteries are connected such that positive terminal of one is in contact with negative terminal of other then we add the potentials so the potential will then be their sum. Similarly if a ...
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0answers
139 views

Help understanding MOSFET channel pinch-off

So my book does not do a good job at explaining this concept at all (I guess it assumes I'm a seasoned engineer ... which I am not). Anyway could anyone explain what is Channel Pinch-Off and why it ...
4
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1answer
2k views

Measuring barrier potential of a pn junction using a voltmeter

The image above is from the book "The Electronics companion". Can someone please explain why the barrier potential of a pn junction cannot be measured due to the presence of the contact potential?
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2answers
2k views

How does current get into a diode?

I think I understand more or less how an ordinary semiconductor diode works: Crystal doped differently in different regions, carrier depletion where they meet, bla bla bla. However, actual diodes ...