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Questions tagged [semiconductors]

Most generally a class of materials that are neither insulators or conductors in their natural state but which can be manipulated via doping or electric fields to change the conduction state. Silicon, Germanium, GaAs are some usual materials. The term is also used to speak about devices that are made from such materials. For example a processor from Intel can be called a semiconductor.

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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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Understand of Unijunction Transistor

Unijunction transistor is a semiconductor device that can be represented as shown: It forms a voltage divider with a diode pointing towards middle of divider marked as \$\eta V_{BB}\$ (where \$\eta\$ ...
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Are there any current methods to microetch semiconductors? [closed]

We can build computers macro size but only big business foundries seem capable of producing and having the privilege of making microchips and better form factor machines. Has technology found any ...
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Designing a circuit that opens when less than 12 volts are applied and closes when more than 12 are applied

I'm looking to build a circuit where current only flows when there is a potential difference across the entire circuit of more than 12 volts (+- 0.1 V). I also need there to be only a small amount of ...
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24 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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98 views

Cause of triode mode in MOSFET

My reference text introduces the MOFSET as follows: The text says the induced channel has uniform width as long as \$v_{DS}\$ is small, because in that case \$v_{GD} = v_{GS} - v_{DS} \approx v_{GS}\$...
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32 views

What are all the different diode current regions in the forward bias operation?

I know there is the usual drift-diffusion current, the Sah-Noyce-Schockley current and the Mott-Gurney high injection region; all these region governed by their own separate regions. I was wondering ...
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Latch-Up in CMOS-Devices

I recently read something about the latch-up effect in CMOS-Structures but I don't understand why are MOSFETs affected by this effect. I understand that high currents through the source-drain path ...
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Majority Carrier Devices

Why majority carrier devices have higher ON state resistance compared to the ON state resistances of minority carrier devices?
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Why is Ic constant in the plot of Vce vs Ic in a common emitter NPN transistor (in active region)?

In this plot, when \$V_{ce}\$ increases in the active region, shouldn't \$I_c\$ also increase as more electrons are getting diffused into the collector? Then, why is it that for a large range of \$V_{...
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27 views

TVS diode with 10 - 15 V forward voltage

I came across this TVS diode: https://m.littelfuse.com/~/media/electronics/datasheets/tvs_diodes/littelfuse_tvs_diode_smf3_3_datasheet.pdf.pdf It has a forward voltage drop of 10 to 15 V. Why? How? ...
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70 views

MOSFET: How can I find conduction parameter and transconductance based on graphs?

So I have my graphs (below) with various MOSFET characteristics. I don't know device dimensions or geometry, therefore I can't solve for the 2 directly with an equation. Otherwise I would just do that....
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What happens to the semiconductor in an LED when it is given voltage that it cannot handle?

Let us suppose we have an LED with the allowed voltage range of 1.5V to 4.5V and we gave it somewhat 12V. Now we know that the LED will instantly stop forever. But I want to know what will happen to ...
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Polysilicon Emitter equivalent for PNP BJT

I recently read (in the book semiconductor device fundamentals by Pierre about polysilicon emitter technique used in a n-p-n Bipolar Junction Transistor (BJT) to enchance the current gain of BJT. I ...
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1answer
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Are there semiconductor materials with hole mobility greater than electron mobility?

Every material I've ever seen has a hole mobility much less than its electron mobility. For silicon, it's by a factor of two or three; for gallium arsenide it's more like twenty. But are there any ...
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58 views

High frequency switching applications

I was reading that for high frequency switching applications with semiconductors, the ratio of the electron to hole mobility should be high. Why is it so? Is it a necessary condition always? Or ...
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Gate voltage of power semiconductor devices in datasheets

Many static characteristics of power semiconductor devices are presented in available datasheets at a specific gate voltage. For example, they are achieved at Vge=15V for IGBT devices and Vgs=20V for ...
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Identity and advice on replacement of SM diode

I have a Sonos Play:3, which is past its warranty. I dismantled it to find it has the well documented fault with a blown capacitor. However, there is also damage also to one of the surface mount ...
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25 views

Should the mass action law be valid for charged semiconductor surfaces?

Considering the case for Metal Oxide Semiconductor also Streetman's book says that if the contact potential for n-type semiconductor exceeds zero it should develop into depletion region but WHY? It ...
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44 views

Photo-conductivity of n and p type semiconductors

Both n-type and p-type semiconductors are available to fabricate a photoconductive devices. To achieve the highest photoconductivity, do you want to use n-type or p-type? Why? $$σ_{ph}=q(μ_n ∆n+...
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42 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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17 views

Neutrality when diode is given an voltage

When a diode is forward biased, the majority carrier electrons move in to p region from n region, now my question is how does the neutrality exists when mobile electrons entered the acceptor ...
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How does a MOSFET conduct in saturation region?

It is a simple question but I could not find a straightforward answer. When a MOSFET enters saturation region, the channel length starts to decrease, and the channel width is the smallest near the ...
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Is the resistance between collector and emitter is lower that of the path between collector and base? [closed]

If no, pls tell me why. And if yes, my question is how can the path C-B-E be have lower resistance than that of B-E? Shouldn't the resistances of BE and CB add up cause they're in series?
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Why can't a combination of two diodes connected back to back act like transistor? [duplicate]

I saw an explanation of the transistor working here by Bill Beaty. I absolutely loved it. But I'm not entirely sure why the action cannot be achieved by two diodes connected back to back by a metal ...
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72 views

The forward voltage Vf of a diode

I want to know about the forward voltage \$V_{f}\$ parameter of a diode device, given an I-V charateristic curve and in ambient temperature. What is the criteria to define the \$V_{f}\$ for any diode? ...
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32 views

How deep does the depletion region in power diode penetrate the lightly doped n- layer under no bias?

I could find references for describing the depletion layer in a power diode under reverse bias and the consequent classification of Non-punch through and Punch-through diodes. But I couldn't find a ...
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1answer
589 views

Why do power diodes have a p+ n- n+ construction and why not p+ p- n+?

I've been learning about power diodes and how they differ from low power diodes with the addition of a lightly doped n-type layer. This n-type layer improves the breakdown voltage rating of the ...
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1answer
38 views

Ic and Vce equations of IGBT

I know in IGBTs while operating, parameters Ic (collector current) and Vce (collector-emitter voltage) are Tj (junction temperature) and Vge (gate-emitter voltage) dependent. Is there anything else ...
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1answer
39 views

Calculation of Vce from Ic-Vge Characteristic

We have found the Ic-Vge (collector current vs gate-emitter voltage) characteristic of an IGBT device as shown below at a high Vce (collector-emitter voltage) value (here 20V) from the datasheet (...
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2answers
1k views

Are some CPUs implemented in standard cells and are others customized?

Explaining the question more, I see some die pictures which are implementing a Cortex-M0, with Bluetooth LE and so on, depending on the chip functionality, and are appearing like this (nRF51822): ...
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Ic-Vge IGBT Curve

In the figure below, presented in the manufacturer datasheet, you can see the Ic-Vge curve of an IGBT device. As mentioned, it has been drawn at Vce=20V. What does this equality mean? Can we have such ...
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45 views

Are both electrons and holes responsible for conductivity in an extrinsic semiconductor (both n-type and p-type)? [closed]

In a semiconductor, the drift velocity Vd and E(electric field intensity) are directly proportional to each other.. with the proportionality constant as mobility of charge carriers.. in the formula I ...
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1answer
62 views

Can really small transistors be modeled as in undergrad textbooks?

Most undergrad textbooks on microelectronics (those covering semiconductors, diodes, BJT's, FET's, etc.) that I have laid my hands on discuss semiconductor concepts such as charge carries, drift, ...
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192 views

What do we mean by “gate plateau voltage”?

While reading some semiconductors datasheets, I've found something called "gate plateau". What do we mean by this term ? Reference: AND8029 application note page 2, from ON Semiconductor written by ...
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1answer
160 views

Large SiGe ASICs for digital logic

I am trying to understand if digital ASICs with tens of millions of silicon-germanium gates exist. A comment in another post states (emphasis mine) "SiGe can hit 5 GHz pretty easily even with half a ...
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Exotic semiconductors for fast digital ASIC

I am researching exotic semiconductors for a digital ASIC with a few million logic gates which should run as fast as possible within a $30 million budget. (Specifically, I need to do a single fully-...
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1answer
61 views

How could the Gate-Source potential difference be neglected?

I’ve been reading the book Electronic Principles by Malvino In the Voltage-Divider bias section of JFET, if gate current is negligible then how did Gate Voltage attain a negative value, given Vdd ...
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1answer
259 views

MOSFET common source amplifier output impedance calculation

What I've read in microelectronic texts like Prof's Razavi's Fundamentals of Microelectronics is that for calculating output impedance, one has to make all independent sources 0, i.e., short all ...
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2answers
65 views

Why conductivity increases in semiconductor when doped?

I know it depends upon the concentration of electrons and holes . So if we add donor atoms, even though electron concentration in conduction band increases , hole concentration decreases due to more ...
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1answer
37 views

Why in semiconductor studies, we are only concerned with reduced zone representation of e-k diagram?

Does electron transition from conduction band to valence band takes place only in first Brillouin zone? Or can it happen in any other Brillouin zone?
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1answer
257 views

Diode current components

I have the following two questions in the derivation of current in a diode. 1) In forward bias, an assumption "abrupt junction" is made and field is equal to 0 is also made. But then we still use ...
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2answers
82 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
59 views

Simple diode question

I have the following doubts about a p-n junction diode: 1) If we short the diode ( connect it's terminals together without any power source) then how is the Kirchoff's law across the loop satisfied? ...
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3answers
1k views

How should I understand the intrinsic body diode inside a MOSFET?

I know there is an intrinsic body diode inside all the MOSFETs, but I'm confused about the reason why it's there. I've searched the articles but can't find a good explanation for it. Can anyone use ...
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2answers
301 views

Why won't this DIY transistor attempt conduct

I've been trying to make a crude transistor device at home. So far I have not been successful. My electrical understanding is next to non existent other than what I've learned in the last 3 months ...
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1answer
65 views

Why carriers move when Electric field is applied on Haynes-Shockley experiment

I would like to know why excess carriers/minority move when an electric field is applied at the Haynes-Shockley expirement
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Confusion regarding this Op-Amp circuit

So I have started learning about Operational Amplifiers. In case of idea Op-Amps, Vd=0 as amplification is very large and Vo is limited by Vcc(the supply voltage). Here in this inverting Op-Amp ...
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1answer
521 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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1answer
127 views

Confusing regarding measuring barrier potential of a pn junction using a voltmeter

I have been trying to understand why we can't measure the Barrier potential existing in an unbiased pn diode but on seeing the answers I am quite confused. There seems to be two answers to this ...