Questions tagged [depletion-region]

The depletion region (also called depletion layer or depletion zone) is a spatial region of special properties surrounding a p–n junction when it is turned off. Physics of the depletion region is crucial for understanding properties of a reverse-biased junction.

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Why does the width of the depletion region decrease with the increase in doping concentration?

Should the depletion region be increasing in width as more and more ions are uncovered at the junction due to the diffusion of majority carriers from one side of the junction to the other? Then why ...
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Drift Current Conception in PN junction

In a PN junction, under no bias, when the depletion region forms an electric current is also formed in the direction from N side to P side. This electric field, also has a potential difference, ...
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Movement of electrons and not holes in a PN junction?

So I've been clearing my concepts about the PN junction upto a deeper level today, and I've got a few questions to ask and clarify my concepts: In a pn junction, due to diffusion, Only the electrons ...
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An accurate representation of the movement of holes in a PN junction

I want to clear my conception of the depletion region in an unbiased PN junction. Before the formation of a depletion region in a PN junction, in the P region there is an excess of holes, aka places ...
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Contribution of hole diffusion current and electron diffusion current in a pn junction

I have recently got to learn that the hole diffusion current and electron diffusion current both point towards the N side in a PN junction? And the diffusion current is hence towards the N side. And ...
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Why is the depletion layer near the emitter region narrower than the collector region?

While studying Grob's Basic Electronics chapter 28 I came across this statement, Notice in Fig. 28–2 that the EB depletion layer is narrower than the CB depletion layer. The reason for the different ...
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Do the depletion regions meet during pinch off in JFET?

In an N-channel JFET, when the voltage across gate and source terminals is 0V and the voltage across drain and source terminals is increased, at a certain voltage (pinch off voltage), the depletion ...
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Is the dynamic resistance of a diode due to the narrowing and widening of the depletion zone?

All diodes have a built-in voltage. When a diode is connected under forward or reverse bias, the depletion region either widens or narrows. Obviously, the barrier height also increases or decreases ...
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What happens between the pinch-off point and the drain?

The typical picture from the pich-off phenomenom assumes that when channel pich-off occurs the density of mobile charge in the region from the pinch-off point up to the drain becomes zero. This ...
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Why is the collector region doped?

As long as within the active region the collector-emitter junction is reverse biased, is there a purpose for which the collector must be doped? Moreover, not only that it is doped, but it is ...
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If a diode has capacitance, why doesn't it block the circuit after some time?

It is well known that diodes have a depletion region, which in itself has some form of capacitance due to the presence of charges on its opposite sides. In RC circuits, the capacitor always acts as an ...
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Explanation for drift current

My question is why the concept of drift current or movement of minority charges is necessary while the pn-junction is formed. So drift current was explained to me in more or less this way As the ...
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Qualitative explaination of Output Characteristic of Transistor (BJT) using Depletion layer between Collector and Base

From my understanding, The diffusion layer at a p-n junction is an equilibrium of two opposing forces on charge carriers due to 2 forces - Concentration Gradient and Electric Field caused by Bias and ...
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Perpetual machine from a PN-junction diode

Consider a PN junction diode Now, this system will naturally form a depletion region due to diffusion and will convert into this: Now, I wish to connect the ends of this diode with a conducting wire ...
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Depletion region in metals

Can we create a depletion region (just like in diodes) between two dissimilar metals?What would be the use of that?
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Diode Depletion Region Forces

I'm currently doing some independent research on silicon based devices and I have come up with one question I can't seem to find the answer to elsewhere. I understand that when an n-type and p-type ...
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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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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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Where do mobile electrons come from to form an Inversion Layer in an N-MOSFET?

I am trying to understand the concept behind the threshold voltage in a N-MOSFET. Upon reviewing various books and the band diagrams, I analyzed the following but still could not understand where do ...
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Test a battery with diode test

I have just learnt how PN junction work, depletion region etc. And finally I got what actually multimeter's diode test is measuring. If there is potential difference between P and N material, and ...
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Why isn't a depletion region considered at the P-N junction of a MOSFET?

I'm trying to understand the working of an n-channel depletion type MOSFET. I'm confused why no tutorial talks about the depletion region between the P and N type silicon i.e between the 'bulk' and ...
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Pinch off in MOSFETs

as the Vds increases in an NFET, the channel is finally closed and the Id is constant and the channel is saturated When the depletion region around the drain expands and the channel moves mostly to ...
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Model for Diode Shows Voltage Increase not Drop

It's well-known that if a diode is forward biased at a sufficient voltage, there is a voltage drop across the diode, i.e. it dissipates power. However, I was reading Wikipedia's article on the ...
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Why doesn't the depletion zone cover the entire diode?

When you form a PN junction you're basically closing a circuit so why don't the free electrons in the N and the holes in the P diffuse completely as they would in any other circuit?
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Name of diode depletion region voltage

This question is related to an electronic devices course. The unit is on diodes. What do we call the potential difference of the electrical field across the depletion region?
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NMOS Channel Type

I've seen some conflicting information about the inversion channel for an NMOS device. Is NMOS n-channel or p-channel? And is the substrate n or p? I know PMOS is just the opposite for both and the ...
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Depletion Mode MOSFET Modelling in SPICE

Does anyone know how to model a depletion mode N channel MOSFET in spice? I have looked online however the majority of resources have shown how to model a depletion type or enhancement type. I ...
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Diode built-in voltage and barrier voltage (forward bias voltage) are they almost equal? how do they relate to each other?

I am little confused between the built in potential that is built up in the diode depletion region and the barrier voltage that needs to be applied across the PN junction to start conducting. My ...
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Understanding reverse biased PN junction

I'm trying to understand a reverse biased PN junction, conceptually. For reference, I'll adopt the convention that the P-type is on the left, and N-type is on the right. So without a bias, the ...
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