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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Any advantage in AC-DC or DC-DC with past, large form factor semiconductors?

I want to clarify this question with my real-world example: Say you have a device which contains some AC-DC converter (or DC-DC) for rather high power specs (10 kW up to 300 kW, not in the same ...
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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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question regarding semi-conductor in electrrical science someone please explain the solution properly [closed]

At 300K, a p-n junction of Silicon (Si) has acceptor and donor concentration of 1 x 1019 cm-3 and 1 x 1016 cm-3, respectively. The intrinsic concentration of Si is 1 x 1010 cm-3.Draw the following ...
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p-type and n-type solids

Is the difference between p-type and n-type solids simply the difference in the placement of the valence and conductive band in the solid. Otherwise I fail to understand, p-type means lots of holes ...
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How do the collector and emitter terminals of a BJT operate when no power supply is present?

let's consider an example of transistor amplifier: Let's consider the case in which power supply is not connected (so between VCC and GND there is an open circuit). What will I read at the output ...
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190 views

What is more conductive, copper or doped silicon? [closed]

At room temperature, which is more conductive: copper, N-type silicon, or P-type silicon? What are their respective conductivities?
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Does hole concentration fall below the intrinsic concentration, if Si is doped with pentavalent impurities?

If we increase N type doping in a pure Silicon then according to the equation $$P_n=\frac{n_i^2}{N_D}\text.$$ Then mathematically, hole concentration is less than \$n_i\$, if \$N_D>n_i\$. Why does ...
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Semiconductor switching device with extremely low leakage current in off state

I would like to use a semiconductor device that acts like an ideal relay, that is, with very low leakage current in the off state. By very low, I mean at least 100 pA per volt (like a 10GOhm resistor),...
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Why “substrate” is exposed through a “do not connect” pin at all?

I've were reading through MOC3041 opto-isolated triac when I noticed this part: "Substrate". It's also repeated later on one page down further, but there's no explanation. I guess that might be the ...
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Explanation for parallel darlington behavior

I've built and simulated the circuit below in real life, LTSpice and Stack-Echange-Spice. It behaves in a similar fashion in all of these Environments. When the "LAMP2" load is disconnected, the Base ...
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The potential drop in a pn junction diode-

In the picture shown above, I was trying to learn about diode equivalent circuits. I am not being able to understand the direction of Vb taught by the instructor here. The question is- If the n region ...
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direction of current densities for electrons and holes?

Let's say we have: \$ J_n = 3 \frac{A}{m^2} \$ and \$ J_p = 2 \frac{A}{m^2} \$ and let's define the direction of positive current (flow of positive charges) to be moving from left to right. Then, ...
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Where do the positive charges come from in P-Type silicon?

Can you please help me understand P-Type silicon? I would like to propose a scenario and then ask you a few questions about it. Scenario: If I take a block of pure silicon and dope it with boron, I ...
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Why do point contact diodes use wire whiskers?

I've recently been learning about the operating principles of various semiconductor devices, and I've run into difficulty regarding the point contact/metal-semiconductor diode. I can't find out why ...
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Deriving the NOT logic gate using PMOS logic

I recently started learning about Field Effect Transistors (FET's) and about the MOS circuit family. From my understanding NMOS is made from a p-type substrate and n-type source/drain, whereas the ...
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Metal semiconductor Junction

As we know in normal p-n junctions is formed by doping on a single semiconductor so that material continuity is maintained which facilitates the movement of charge carriers between two regions. But in ...
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ploting the recombination rate in a forward bias depletion

I'm trying to figure out how to plot the graph in b. I know I need to go according to the recombination formula in a, and Ei is linear, but for some reason something won't work. is there anyone who ...
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Does solar cell absorb sub-bandgap photons?

My understanding is that although we are taught that solar cells only absorb photons of energy higher than the bandgap of the material, some of the sub-bandgap photons still gets absorbed, which is ...
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What is the part number of this FET with top marking “NSC1”

LCD switch circuit part in laptop. The marking is marked "NSC1". "a" is the gate and 5 volts is applied "b" is the drain "c" is the source 3.3 volts is applied to b, and if a gate has 5 volts, 3.3 ...
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Depletion region (space charge region) width calculation

Calculation of depletion region width requires the knowledge of permittivity of the material as shown below. \${\displaystyle w\approx \left[{\frac {2\epsilon _{r}\epsilon _{0}}{q}}\left({\frac {N_{...
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1answer
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Dielectric constant (relative permittivity)

I recently learned that the dielectric constant (or relative permitivity) is not actually a constant, but it depends on wavelength or frequency (dielectric function). If that is the case, why are we ...
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Derive the expressions for the i-v characteristics of these configurations of NPN Transistors. Part (a)

I just need part (a) to be solved because then b would be trivial. I am using the Ebers-Moll model equations but somehow my final solution doesn't have alpha_F and alpha_R and i know that shouldn't ...
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Unknown logo on FGS25N120ANTD IGBTs. Which semiconductor manufacturer is this?

I bought 5 FGS25N120ANTD IGBTs from my local vendor a while back. I was unable to identify the manufacturer, based on the logo. Can somebody help me out?
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Output characteristics of transistor

Why is the slope of output characteristics of transistor in CE configuration more than that of CB configuration??
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Semiconductor mass action law

Based on the results from the above example, applying the mass action law yields: \$n_i^2 = n_o p_o = 4.86\$ X \$10^{19}\$ However, we know that the intrinsic concentration of Si at 300 K is \$...
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1answer
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Why do bare die chips (MOSFET) have a maximum storage temperature?

As far as I understand, a chip in general and a MOSFET in particular has a maximum operating temperature (let‘s say 125 °C or 150 °C for Si) because above that temperature the risk increases of ...
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Does the Shockley Ideal diode equation involve drift current?

I've encountered a contradiction in semiconductors. The ideal diode equation considers saturation current (the current when applied voltage is reverse biased to the diode). I thought that saturation ...
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1answer
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What exactly do the well taps in MOSFETs do and how?

Do they affect the flow of charge carriers or charge concentrations at all in the device? How so? Up to this point I've tried to visualize the effects that the various doped areas had on device ...
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2answers
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PN Junction paradox or something else? [duplicate]

[![I am having problem understanding reversed biased pn junction as the explaination provided by my book or any other source about flow of current in forward biased condition seems equally applicable ...
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How to compute the substrate doping concentration given parameters to compute Effective Gate Length?

I have been struggling with this homework question all weekend, and given it's Easter, I turn to the mercy of your all's wisdom given my University resources are unavailable. Any help you all could ...
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What happens when we apply a negative voltage to MOS capacitor?

I want to check if my understanding is correct( Showing just the case of semiconductor): As we apply the voltage as shown, holes get repelled due to the electric field produced by the battery towards ...
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Why are quasi neutral regions in a PN junction are called “quasi neutral”?

When the PN junction is in equilibrium ,the region away from the depletion region is neutral . Now when a bias is applied say forward , then we refer these regions as "quasi neutral ".But why? What ...
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Carrier concentration in the depletion region of PN Junction graph

I have just started learning about PN junction with the help of this video NPTEL At time 10-15 minute from the start ,we get this The professor claims that from the linear scale it is clearly seen ...
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Semiconductor mass action law question

I was told that the mass action law $$np = n_i^2$$ only applies to compensated semiconductors and intrinsic semiconductors, and it does not apply to n-type or p-type semiconductors. Is this true? I ...
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Why don't electrons from conduction band jump to the acceptor level?

One basic idea of Band theory is that electrons always try to occupy the lower energy states. Acceptor levels have vacant low energy states . Then why do electrons from Conduction band don't fall back ...
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1answer
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Difference between Logic Chip and Memory Chip front-end manufacturing process?

I understand that memory chips like DRAM Chips require a little different set of Front-end setup than logics chips. However, I am not finding anywhere how the actual manufacturing steps differ, ...
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1answer
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How is electron concentration maintained to hole concentration in intrinsic semiconductor?

I know about E-H pair generation because of which in an intrinsic semiconductor the numbers of free electrons=number of holes. In terms of Fermi level, fermi level shifts when the temperature is ...
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Can anyone properly explain me the characteristic curve of the p-type JFET?

I know how a MOSFET works. But recently I wanted to know details about JFET. When V(GS) = 0 volts there will obviously a current flowing through the p-type channel. What confuses me is how the ...
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Depletion Region Width for an Intrinsic Heterojunction

While I was going through my old semiconductor textbooks to aid in designing a double heterostructure device, I realized that there does not seem to be a well-defined description for how wide the ...
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1answer
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What is the technology of slicing a chip to debug called?

A couple of times, I have heard that there are situations where a microprocesor or chip has to be sliced to look in to the contents, or for the purpose of debugging it. Layer by layer sectioning is ...
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In an intrinsic semiconductor, why don't electrons go out from both valence and conduction bands?

My textbook ("Electronic Principles" by Malvino and Bates) seems to suggest the free electrons in conduction band move left and reach the positive terminal of the battery. Does this mean electrons in ...
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1answer
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What mechanism is responsible for the β/hFE variations in manufactured bipolar transistors?

It's common sense that the current gain β (hFE) in a bipolar junction transistor is somewhat unpredictable, and one must design a discrete transistor circuit to be insensitive to the variation of β. ...
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1answer
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Switching Devices [closed]

I am currently working on a project looking at research materials on low voltage but high current switching devices. Is there any technologies/research out there that are rated for high Amp low ...
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1answer
64 views

Current across a silicon diode

Which method or theorem can I use to solve the current across a silicon diode considering the two DC voltage sources?
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What is the difference between CPU transistors and generic ones?

Recently I had to build a h-bridge driver for my project, wireless power transmission. I learnt that I needed to have dead-time in my PWM signal given to IR2110, which doesn't have any dead-time ...
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Why this switch's current sense ratio sometimes increases and sometimes decreases?

The Infineon BTS50055-1TMA is a "smart" power switch that is basically a FET with current monitoring. The equation for calculating current is given by the first entry in the truth table on datasheet ...
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2answers
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Intuitive way to think of transistor saturation current?

I am having a hard time understanding what saturation current (denoted Is in my textbook) actually means for a transistor. For a diode, it makes perfect sense, it's the approximate maximum reverse ...
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76 views

If a silicon cyrstal is connected to a battery does current flow through the wire?

In a circuit consisting of a pure silicon crystal with each end attached to a different terminal of a battery via conducting wire, is there a current flowing through the wire? It seems that there is ...
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Why do NPN/PNP transistors need to use doped semiconductors for the 'N' region?

By my understanding, as long as the P layers are properly doped (to have fewer free electrons), the electrons could not flow between collector and emitter until the P is given a satisfactory level of ...
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1answer
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the transconductance of cascade MOSFET IF channel length modulation is NOT ZERO

What would the derivation of the cascode MOSFET transconductance in small signal analysis IF THE CHANNEL LENGTH MODULATION IS NOT ZERO, as most examples for the cascode mosfet transconductance say in ...

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