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2
votes
3answers
74 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 ...
0
votes
0answers
32 views

Diode at reverse biasing

Why the electrons don't move that way : giving that : 1- if the electrons of n type managed to get to p type and electric field will help them circulate again as electrons flow against electric ...
0
votes
0answers
50 views

Diode as variable capacitor

I'd like to ask about: Regarding the diode as variable capacitor, I've read that at reverse it will acquire more charges in the depletion region but imagine we did so then remove the diode from the ...
1
vote
1answer
40 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
53 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
62 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 ...
0
votes
1answer
104 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
121 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 ...
0
votes
1answer
38 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
168 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
348 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
1k 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
286 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 ...
0
votes
0answers
89 views

Grading/Doping of pn junctions

I was studying about pn junction grading and junction capacitance and I came to look at step graded and linear graded junctions. I read that step grading in done for the base emitter junctions of a ...
2
votes
3answers
79 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 ...
21
votes
4answers
2k 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
249 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
39 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
74 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 ...
4
votes
7answers
875 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
119 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
105 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
1k 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
244 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
86 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 ...
5
votes
1answer
12k 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
553 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
352 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
1k 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
715 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
0answers
283 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 ...
1
vote
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
396 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
370 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 ...