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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How \$V_{th}\$ is calculated in MOS structures?
I'm an electronic engineering student, I've already studied the theory, but it seems that I'm missing something randomically from most of the chapters, so today I'm showing you a question of an exam's ...
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Why not use synchrotrons for EUV? [closed]
The semiconductor industry has at last started upgrading to extreme ultraviolet lithography. The delay was in large part occasioned by the difficulty of building a suitable EUV light source, and ...
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Semiconductor chip shortage [closed]
Does anyone have an answer why do chip distributors have almost virtually zero stocks? Is there a shortage?
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High Voltage PMOS devices availability
Generic question for experts well versed in semiconductor device physics. Most of the high voltage power switching devices seen are N-Channel (Silicon and Silicon Carbide) with varying ratings. Is ...
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1answer
30 views
Troubleshooting Skyper 32Pro R + Adapter Board 1 Skyper 32Pro R
Hello I am trying to test an IGBT SKM145GB066D with the Adapter Board 1 Skyper 32Pro R and gate driver Skyper 32 Pro R, but cannot make it work. I've spend 2 weeks trying, but it seems like some ...
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2answers
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Calculate V for given circuit [closed]
Consider the diode circuits in Figure. V1 = 5 V, V2 = 0, and VCC = 6 V. Assuming ideal diode model, determine V0.
I assumed both d1 and d2 to be ON but how to calculate further? I have no idea please ...
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1answer
116 views
Magnitude of current
The current of a germanium diode at room temperature is 100 uA at a voltage of -1 V. Predict the magnitude of the current for voltages of 0.2 V and -0.2 V at room temperature. Repeat the prediction ...
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Designing BJT that's beta value is 120
I want to design a BJT that's beta value is 120
Following this picture can I say that the components of the base current are like this?
J(B) = J(pE) + J(R) + J(RB) - J(G) - J(pC0)
I want to design ...
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4answers
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What is the physical model for energy flow in or around a lossless conductor during transient analysis? (Veritasium Electricity in Wires)
Context
Veritasium - The Big Misconception About Electricity - Energy Doesn't Flow in Wires
Note I do not agree with the answer (D) given by Veritasium which is only plausible if any tiny current ...
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2answers
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Why can't electrons leave the N side and enter the P side in reverse bias?
Why can't electrons (excess electrons) of the N side of a semiconductor diode enter the P side via the battery in reverse bias mode of PN junction? like this:
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1answer
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Diodes made using separate p and n-type semiconductors
Can a diode be made by connecting, in series, separate n and p-type semiconductors?
Assume that all ends are attached to Ohmic contacts. I am hoping that this will prevent any discontinuities in the ...
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2answers
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Why aren't aluminum and nitrogen used as dopants in semiconductors, chips, etc.?
Boron is most commonly used for the p-type dopant, and phosphorus for the n-type, correct?
Why not aluminum for the p-type and nitrogen for the n-type?
Is it just a matter of cost and/or convenience?
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Energy band diagram of a polar material
For a single piece of a polar material (ex. GaN, AlN, etc), there exists a constant electric field inside the material due to the bound charges at the surface.
Above figure shows the resulting band ...
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2answers
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MOS capacitor - why is the total capacitance just the oxide capacitance C_ox?
All of the textbook that I have read mention that the total capacitance is just the oxide capacitance (Cox) for a MOS capacitor in an inversion and accumulation mode. It makes sense that is true for ...
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What does "field" in field oxide mean?
This is an excerpt from Design of Analog CMOS Integrated Circuits by Behzad Razavi. What does "field" in field oxide mean here, electric field?
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The accumulation region of metal ptype in a negative voltage applied to the gate
For a metal-p-type semiconductor boundary, I know how to compute the depletion width when no voltage is the applied to the metal, as below:
How to compute the accumulation width of a metal-p-type ...
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5answers
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Why is silicon necessary in making semiconductors?
Can you make a diode just by connecting a piece of N-type material like phosphorus to a P-type material like gallium? Why are they added to silicon?
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2answers
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Why N type MOSFET is used for low side and P-type for high side switching?
Typically N-MOSFET is used for low side switching and P-Type for high side switching. That's why transmission gates use both N and P-type MOSFET. But I can't correctly understand how a P-Type for the ...
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Why does the majority carrier concentration near the junction not decrease under forward bias? (PN junction)
We see that the current due to the majority carrier decreases near the junction as shown above, which means the majority carrier concentration should also decrease since the diffusion current is given ...
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1answer
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PN junction depletion capacitance
I am having difficulty understanding the PN junction capacitance.
I can't seem to figure out what exactly forms the two plates of the PN junction capacitance and what is the positive and negative ...
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2answers
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What does the cross point of V-I curves mean?
Here you see a V-I graph including many curves achieved under different junction temperatures of an IGBT. As it can be seen there is a cross point where all curves intersect each other. Does it make ...
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1answer
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Ambiguity of the "intrinsic" layer in a PIN diode
I'm having trouble understanding the fundamental makeup of large PIN diodes, specifically those used in radiation detection devices. For example, high purity germanium (HPGe) detectors are often ...
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1answer
39 views
Thyristor latching current and holding resistance
Is there a formula for calculating the latching current of a thyristor and the resistance of the thyristor after it forward conducts and I_gate becomes 0? I couldn't find anything online; the ...
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1answer
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What is the reason of difference in distributed gate thyristor design
As in the pictures, they use different designs (current rate, voltage rate etc. are same.)
What is difference between these two designs?
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1answer
51 views
Majority Charge carriers and electron holes
Suppose I have an extrinsic semiconductor made of silicon and doped with phosphorous. Now, phosphorous has one more electron than silicon. After replacing one silicon atom, and taking its place, the ...
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1answer
115 views
Derivation of microscopic Ohm's law from macroscopic version?
What I tried was:
$$\overrightarrow{E}= - \triangledown V \qquad \qquad\qquad\qquad (1) $$
$$V= IR\qquad \qquad\qquad\qquad\text{(Ohm's law for materials where V}\propto \text{I)}$$
$$\text{...
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Find the output voltage of a diode circuit with two batteries connected in parallel
When Vi<-2V, the D1 & D2 both will be turned on and both of them will be considered as short circuits. But how do I find the output voltage with two batteries connected in parallel like this? I'...
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1answer
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In n-type semiconductor, when are dopant atoms considered positive ions?
Consider a pure piece of silicon semiconductor. Let’s say we dope it with Phosphorus. The extra electron in the outer most shell of the phosporous is in its conduction band as it is not part of any ...
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2answers
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How does logic 1 get passed through an NMOS pass transistor?
I'm studying pass transistors. One thing I came across in several of the books is that when an NMOS has a logic state HIGH and the input terminal (the schematic below) is also HIGH, the output ...
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1answer
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Given a energy band diagram, can you always calculate potential, electric field, and charge distribution?
Given a band diagram, where do you start to get the electric field and charge distribution?
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BJT Early effect and the small signal model
As the collector-emitter voltage changes, collector current changes due to the Early effect so the base current must also change.
In the small signal model, we only account for the change of collector ...
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1answer
119 views
Electric field of Schottky diode
Reference: Device Electronics for Integrated Circuits 3rd Ed. Richard Muller
I am trying to understand how to calculate the maximum electric field. The answer given in the book is $$E_{max} = \frac{-q ...
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1answer
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Collector current in datasheet Graphs
Here is an example of output characteristics fot IGBT devices, i.e., the "collector current (Ic)-to-collector emitter voltage (Vce)" graph. Can somebody help me find what Ic represents here? ...
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Why aren't semiconductor wafers diced into triangles?
Semiconductor wafers are circular, and usually they are divided into squares or rectangles. However it's more efficient to pack triangles into circles than it is rectangles, so less wafer area would ...
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1answer
109 views
Voltage fluctuation due to AC in a half wave rectifier
I think I get the broader idea of using a diode as a half wave rectifier, but I have a question:
Who provides the forward voltage or knee voltage to start the diode for rectification? I am assuming it ...
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3answers
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Do we operate diodes past their barrier or cut off voltage?
I think I get the idea of barrier or cut of voltage (e.g., 0.7 V for Si). So diodes start conducting after cut voltage. I have few questions for the cut off voltage
What happens if I increase the ...
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1answer
57 views
Physics of BJT and charge profiles
Why does a linear charge profile in the base imply no recombination of charges at the base, but in case exponential decay it implies recombination at the base?
Why does charge density at the base ...
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1answer
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Compute the junction temperature for a bridge diode
Here is the datasheet:
I calculated the power dissipated through one of the 6 diodes according to this formula
$$P_d = U_\text{D0}\cdot I_\text{average} + R_{d}\cdot I_\text{rms}^2$$
Then, I would ...
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5answers
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What makes the value of the surface to case thermal resistance?
From the datasheet:
The datasheet notes that the case to heatsink thermal resistance is equal to 0.4 K/W. I do not know how they obtain this value as the thermal resitance depends at least on the ...
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MOSFET diode configuration expression for dynamic bias
I'm trying to think of an elegant way of analytically expressing the gate voltage as a function of time \$V_g(t)\$ (= \$V_d(t)\$) for the diode configured MOSFET below.
The sources VDD and V1 are ...
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(Too?) simple model of a pn junction
I want to build a simple model of a pn junction in order to show high school students how it works. I am not looking for something precise, so I use really simple discretization and I discard units. I ...
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1answer
81 views
Thermal impedance - what is the purpose?
If I want to compute the junction temperature of a component, I can by using its thermal resistance (case to junction) and if I know the power dissipated by the component and the temperature of the ...
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4answers
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Are there logic gates by which a signal could propagate backwards?
Is there a type of logic gate with floating inputs (I'm using that term loosely) such that a fixed voltage on an output could "propagate backwards?" Let me clarify with examples...
Say you ...
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1answer
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How will new (n on n) pixel detector work at *beginning* of HL-LHC?
The pixel detector of ATLAS and CMS detector is expected to be replaced by a technology N in N, instead of N in P.
We see in the preferred answer of
In this schematic, where is the depleted layer once ...
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4answers
588 views
In a JFET, is the gate *always* connected to the bulk/substrate?
In a JFET, is the gate always connected to the bulk/substrate ?
Or is there "no rule" (sometimes it is, sometimes it is not)?
And what about the case of the MOSFET ?
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1answer
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What is the current state of the art design rule for SiC VLSI? Technological impediments to making a SiC microcontroller for a Venus lander at 460 °C?
A sub-discussion below Is there any demonstrated or even proposed technology that can sterilize a spacecraft with 100% certainty and yet leave it electronically functional? in Space Exploration SE ...
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Why does the number of holes in an N-type semiconductor increase with temperature?
I was watching this video.
I understand that the dopant atoms introduce huge numbers of free electrons that essentially overshadow any additional electrons that break free due to higher temperatures.
...
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1answer
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Solar cell DIY with monocrystalline silicon wafer
I would like to make my own solar cell-
From a quick search on youtube, these 2 videos are apparently always the #1 result for "solar cell diy" keyword or similar:
Video 1
Video 2
The ...
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1answer
107 views
Why does the value of shunt resistor need to be very high for solar cell's greater efficiency?
In the circuit equivalent of a solar cell, shunt resistor is described as "The irregular polycrystalline lattice grain boundaries that resist to the flow of electrical current in the silicon ...
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1answer
270 views
Why does channel length modulation only occur in the saturation region?
As drain voltage is increased, the reverse bias across the drain-body junction also increases and thus the width of the junction should also increase which should deplete the channel length as well. ...