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5
votes
4answers
125 views

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 ...
0
votes
1answer
29 views

Diffusion Capacitance: Forward Bias

Please see attached image. I'm struggling to understand how the book went from line 2 to line 3; it doesnt seem obvious how they did the differential. Thanks
0
votes
1answer
57 views

Why the current across a diode is zero when the forward bias voltage is less than barrier potential?

In the I-V characteristics of diodes under forward bias , I have seen that the current starts increasing from zero only after reaching the barrier potential , say 0.7 for silicon. As far I understand ,...
0
votes
1answer
43 views

PN junction diode

When we look at the PN junction diode, there is always a depletion region , for which one side in negative and one side positive. The reason behind this is that the n-side depletion region is ...
3
votes
2answers
102 views

How the Depletion Region of PN Junction changes under Bias

There are several other questions on PN Junctions out there, but I don't think this one has been asked specifically. I am having a severe misunderstanding of how the depletion region width varies ...
0
votes
2answers
48 views

Is a pn-junction diode ever said to be “on” in reverse-biased conditions?

I know that it takes about 0.6V-0.7V for a pn-junction diode to be on in forward biased conditions, but what about reversed-biased? I mean is it never called "on"? Here is the specific question that ...
3
votes
3answers
213 views

What is the precise definition of forward and reverse bias for a P-N junction?

I have always thought that for a P-N junction, forward-biased simply means that \$ V_{PN} > 0 \$ and reverse biased means that \$ V_{PN} < 0 \$. However, in this article about NPN BJTs, there ...
-2
votes
1answer
74 views

about semiconductors

I have got the following doubt. Hope you clarify it. Thanks in advance electron when finishes its life time recombines with hole in valence band . its given that in an pnp transistor holes of emitter ...
1
vote
1answer
42 views

Currents confusion in a JFET datasheet

I am analyzing a JFET. The datasheet has both information about the currents Igss and the maximum of Ig. I know that the Igss is a the reverse current in the PN junction but I can't explain myself ...
1
vote
1answer
93 views

Forward bias voltage across a pn junction diode

Why must the forward bias voltage across a pn junction diode always be less than the built-in potential barrier? What happens when you apply a forward bias voltage across a pn junction diode that is ...
0
votes
0answers
27 views

P-N diode voltage vs number of holes in forward bias?

While studying P-N junction diodes, I came across the derivation of the relation :- \$V_0 = \frac{kT}{q}\ln(\frac{p_p}{p_n})\$, where \$p_n\$ is the number of holes on the edge of the depletion ...
1
vote
2answers
60 views

Quick junction / pn junction diode clarification

I was studying diodes. I was at the part where we talk about P-N junctions diodes. There is a part I am confused about. Is the "junction" part the part in the middle which blocks the current if no ...
0
votes
0answers
30 views

why pn junction turn ON for lower voltages at higher temperatures?

Increase in temperature produces electron-hole pairs. So number of holes created due to temperature equal to number electrons I believe. If you apply some voltage there will be equal number of ...
1
vote
1answer
347 views

Relationship between band gap and built in potential for PN Junction Diode in equilibrium?

I wanted to know the relationship between the band gap (Eg) of the p/n regions in a diode and the built in potential in equilibrium. My intuition says that Eg = e*Vo. I did a small calculation for ...
0
votes
2answers
318 views

How PN junction diode is used as temperature sensor [closed]

I know the operation of PN junction diode. But I wonder how they use it as a temperature sensor.
0
votes
2answers
68 views

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?
-3
votes
2answers
102 views

NPN Transistors [duplicate]

How does NPN transistors actually work? In the picture below, I understand that electrons flow in A as the n-p junction of the Emitter and Base is forward-biased. However, the p-n junction of Base and ...
2
votes
3answers
102 views

Detecting electrons as they tunnel through the band gap of a P-N junction

As a learning exercise I'd like to try creating a random number generator using reverse-biased BJTs. As I understand it, if the emitter is saturated in reverse bias, occasionally electrons will ...
1
vote
1answer
45 views

Why is there a “ - 1” in the pn-junction current equation

I was studying the Ideal Current–Voltage Relationship and was wondering why there is a "-1" in the pn-junction current equation for a pn junction diode.  Thanks in advance!
0
votes
2answers
113 views

What are holes? How they exist in pn junction [duplicate]

I always wonder that what are holes I know electron and I can imagine it But how holes exist...
2
votes
1answer
110 views

Why avalanche breakdown in a PN junctions is said to be caused by minority carriers?

Reverse bias increases the depletion region (the "space charge region"). Remembering that electrons travel from (-) to (+) terminal, and that in reverse mode the (+) terminal is attached to the n-...
0
votes
1answer
860 views

In band diagram, why the Fermi energy (EF) is constant along the device?

In band diagrams of PN/PIN junctions etc. the Fermi energy level (\$E_F\$) is drawn as constant along the device (see image). (source) Why is it constant? What does it represent?
1
vote
2answers
303 views

Why does an Ohmic contact contain non rectifying junction?

I would like to know a simple explanation for the term 'Ohmic Contact'.I looked in wikipedia but I couldn't get what actually it means.I couldn't even get what do you mean by non rectifying junction....
0
votes
1answer
57 views

Why is the voltage across a PN junction 0 v when it is in open circuit conditions? [duplicate]

Why is the voltage across a PN junction 0 v when it is in open circuit conditions ?
0
votes
1answer
601 views

Cutoff and Conducting diodes

Why is D1 considered cutoff and D2 considered conducting ? Note : I am working with constant voltage model where the diode voltage is 0.7v and I need to figure out I and V. Please explain why D1 is ...
1
vote
1answer
2k views

Why can current flow through the reverse biased base-collector junction (N-P junction) in a BJT with a forward biased base-emitter junction?

If the base-emitter junction of a BJT is forward biased, then current can flow through the reverse biased base-collector junction (N-P junction). This disagrees with my understanding of the PN ...
4
votes
2answers
3k views

minority carrier life time? Why is it important for devices' switching speed. Why not majority carriers?

I am trying to get my head around why would and silicon engineer care about the minority life time carrier and how does the minority carrier affect the switching speed of PN junction. Why is it so ...
3
votes
3answers
461 views

Understanding the PN-Junction Built in Voltage

I don't like asking duplicate questions but I couldn't find one that was quite the same. I apologize if it is similar to another. TL;DR: How can a charge neutral substance have a potential? Why ...
3
votes
3answers
104 views

Transportation of holes

I was studying pn junctions and came across the concepts of diffusion currents. From what I understand is, when the junctions come together, since there is an excess of donors on the n side and an ...
27
votes
4answers
3k views

Why isn't there a potential difference across a disconnected diode?

I know this question sounds silly, as if there was a potential difference a current would be created when the terminals are connected together and this would mean energy has come from somewhere. The ...
1
vote
1answer
535 views

Does a reverse-biased P-N junction create quantum noise?

It is my understanding that a highly doped, thin depletion region, reverse-biased P-N junction at low voltage can cause quantum mechanical tunneling. This (or sometimes avalanche breakdown) is used ...
1
vote
0answers
43 views

What happens to the energy bands when a forward bias > Buit-in potential is applied [duplicate]

When we applied a forward bias across a PN junction, the barrier height of the depletion region reduces. What will happen to the energy bands when we apply the forward bias greater that the built-in ...
0
votes
1answer
93 views

How is the PN junction formed?

I am confused about a couple of points: When the electrons diffuse from N side to P side, and holes diffuse from P side to N side, negative charged region is formed at the junction in P type and ...
6
votes
7answers
3k views

Resistance of a semiconductor diode

When we calculate the dynamic resistance \$r=(\frac{dv}{dI})\$, for any n-p junction, how is it different from the normal resistance \$R=\frac VI\$? Does the equation for the voltage drop (The fermi ...
3
votes
1answer
211 views

Is my avalanche noise “random?”

I'm working on a hardware random number generator based on the below design. It uses two reverse P-N junctions to create avalanche noise. I was looking at the circuit with my oscilloscope, and I ...
1
vote
0answers
156 views

Equivalent circuit for solar cell

I have a question regarding the equivalent circuit for a solar cell. The circuit includes a diode to model the p-n junction of the cell. When some part of the photo-generated current flows through ...
0
votes
1answer
4k views

Do we include the voltage drop across a diode when calculating the current through the diode, taking into account breakdown has occured?

So, am doing this question paper for my electronics, and I stumble across a question that asks me to calculate the current through a diode, with a breakdown voltage of 1.7, an Imax current of 20ma, ...
2
votes
1answer
302 views

Potential drops in BJT in CE configuration?

In a simple p-n junction diode, there is a \$V_{eq}\$, the potential difference between the p-doped and the n-doped portion of the diode. When an external potential \$V\$ is applied in forward bias, ...
0
votes
1answer
104 views

Reverse voltage PN junction (how it works?)

I have this block inside my circuit, which is supposed to drawn a current from the main line to the GND whenever there is this signal in the transistor base (simple diagram): The main line can ...
7
votes
1answer
25k views

Why MOSFET Pinchoff occurs

This question is regard to enhanced n-type MOSFETs. From what I understand, an inversion layer is formed underneath the insulating layer below the gate of the MOSFET when a voltage is applied to the ...
0
votes
2answers
1k views

Diode PN Junction Understanding

I have a question about how the PN junction works in a diode. According to http://hyperphysics.phy-astr.gsu.edu/hbase/solids/pnjun.html: "Filling a hole makes a negative ion and leaves behind a ...
-4
votes
2answers
582 views

What happens when a AC current is applied to a PN junction? [closed]

What would happen if a AC current is applied to a PN junction? Is the input current a sine wave?
1
vote
1answer
2k views

Depletion Region of a FET

So I finally Dived into understanding the P-N Junction and Field Effect Transistors. (this may almost be teetering on the "Physics portion" of electronics, but it's still mainly for understanding the ...
2
votes
3answers
1k views

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 ...
2
votes
1answer
311 views

Industrial construction of pn-junction diodes?

I was just doing a project for a website and my team member excavated a standard pn-junction diode to see that inside the ceramic casing, the semiconductors of p and n doping merely abut together in ...
2
votes
3answers
2k views

Simple pn junction / diode question

Lest assume we have the setup presented in the image. What would be the potential difference (not voltage drop) between points A and B? Why? What effect will the pn junction barrier potential have ...
1
vote
1answer
526 views

Excess minority carrier concentrations at the edges of the depletion layer

In a pn juction how do the excess minority carrier concentrations at the edges of the depletion layer p'(xn ),n'(−xp ) depend on the forward-bias voltage? Are these the maximum concentrations of the ...
2
votes
2answers
537 views

Light levels affecting IV curves for a Diode

I conducted an experiment to work out the saturation current under reverse bias for a diode in three different scenarios, ambient lighting, low light levels and high light levels. Is there an equation ...