Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

Questions tagged [pn-junction]

For questions about p-n junctions, which are the boundaries between p-type and n-type semiconductors and are building blocks for diodes, transistors, etc. Only use for questions about p-n junctions themselves -- do not use for questions about circuit elements that happen to contain p-n junction(s) unless the question is specifically about the element's p-n junction(s).

For questions about p-n junctions, which are the boundaries between p-type and n-type semiconductors and are building blocks for diodes, transistors, etc. Only use for questions about p-n junctions themselves -- do not use for questions about circuit elements that happen to contain p-n junction(s) unless the question is specifically about the element's p-n junction(s).

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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 reason I ask this though is that from my…
Blue7
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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 that one builds circuits with do not end with bits of…
hmakholm left over Monica
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Why does MOSFET pinch-off occur?

This question is about 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 gate. When this voltage exceeds \$V_\mathrm{T}\$, the…
user968243
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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 and resistance like this: Thus, I expect the…
Yashkalp Sharma
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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 junction, as I thought electrons cannot flow from the…
Blue7
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Why is the light emitted by the LED not of a single wavelength but consists of a narrow range of wavelength instead? Spectral linewidth change?

I do understand that the wavelength of the lights depends on the energy gap of the semiconductor, but why does it consist of a narrow range instead of a fixed value? is it because during recombination the photons have random phases? Also, how does…
Meep
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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 open circuit after some time (when it is almost…
Wais Kamal
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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 potential drop, and not the absolute Galvani…
stochastic13
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What is a typical diode's ideality factor?

Some background, for anyone unfamiliar: The Shockley diode equation is $$ I_D = I_S·\left(e^{\frac{V_D}{n·V_T}}-1\right) $$ with the quantity \$n\$ called the ideality factor, a number between 1 and 2. Ideal diodes have an ideality factor of 1,…
Hearth
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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 a 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 much about minority life time and not majority…
dr3patel
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Why can't a P-N junction diode be used as a voltage regulator or reference in forward bias?

Usually, a Zener or avalanche breakdown region for a suitably doped P-N junction is used for voltage regulation as a substantial variation in the current (due to minority carriers) requires a negligibly slight variation in reverse bias voltage. From…
ThePhysicist
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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 anything.Will someone please explain it to me?
John
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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 in some hardware random number generators.…
bsamek
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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 a Schottky diode? Three reasons I can come up…
Joren Vaes
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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 combined and some layer is formed that further halts the…
Muhammad Usman
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