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 their conduction state. Silicon, Germanium, and 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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Unexpected slope change in I–V curve of an infrared LED — beginner question
I’m a complete beginner working on a simple experiment to measure the I–V characteristics of LEDs.
For most visible LEDs, my results look as expected: the current increases exponentially once the ...
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When should an MOS varactor be used in place of a varactor diode?
I was reading about voltage controlled oscillators in this article.
Towards the bottom of the article, the authors display this figure when discussing varactor diodes:
I'd never heard of an MOS ...
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Why does Ebers-Moll Model reduce to three instead of four parameters?
In the Ebers-Moll Model of a BJT we have 4 Parameters.
The following images are taken from
U. Tietze Ch. Schenk, "Halbleiter Schaltungstechnik" ("Semiconductor Circuit Technology")
...
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Hybrid Relay- reverse Engineering [closed]
I want to design a hybrid relay for a three phase motor. The rating is 230VAC L-N @20A. In order to get a better idea, I ordered this hybrid motor starter.
It is also a 3 phase hybrid motor starter ...
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P-JFET strange behaviour upon negative Vgs
simulate this circuit – Schematic created using CircuitLab
I am trying the understand the working of a P-JFET. Why is the behaviour strange for Case-3? Is it a simulation issue?
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Interpreting the datasheet of P-JFET MMBFJ270
Why are there two curves for transfer characteristics of MMBFJ270?
Does it mean drain current can be bi-directional based on VDS - If so, I assume a typo in VDS parameter?
Or does it refer common-...
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Measuring BJT Gummel Characteristics with Keysight B1500A: Do I Need Three SMUs?
I want to measure the Gummel Plot of a bipolar junction transistor (BJT) using a Keysight B1500A. My setup includes two medium-power SMUs (MP-SMU) and one GNDU. The connections are: emitter → GNDU, ...
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Wouldn't a large enough voltage source connected across the collector-emitter ends in a bipolar junction transistor forward bias emitter–base junction
I’m analysing an NPN transistor in terms of electric fields and potential barriers. Suppose we have the configuration:
Emitter | Base | Collector
This means there are two PN junctions and therefore ...
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Parallel LEDs in semiconductor package
I'm working on a project that requires me to use 3V LEDs with a Lux rating of about 150 lm @ 300 mA. I'm working with my PCB vendor, and they recommended an LED with the specs I'm looking for.
However,...
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When a JFET is in saturation, does the depletion region completely block the channel or mostly block the channel?
I'm trying to understand the physics of a JFET in saturation, but books are contradictory. Some say that the depletion regions meet, pinching off the channel, but this is not a barrier to the ...
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Comparison of off current between GeOI and SOI finfets
I am going through this research paper at https://ieeexplore.ieee.org/document/7070691
While drawing conclusions from Ion vs Ioff graphs it states that “Ioff is less sensitive to threshold voltage ...
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Output characteristics of N-Channel MOSFET's for negative Drain Voltage and Current
I have seen some questions recently about MOSFET Drain current Id being negative while the MOSFET is turned on. Links to some of them:-
MOSFET driving backwards - posted by NBK SOFT
Dual MOSFETs used ...
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IV characteristics of a P+N diode: how to find boundary conditions
I have the following junction:
Where \$\tau _p\$ for \$x_b < x < x_c\$ is said to be small enough such that the distance \$ x_c - x_b \gg L_p \$ (where \$L_p\$ is the \$ \sqrt{D_p * \tau_p}\$ ...
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Intuition behind quasi-Fermi levels
The definition of fermi level, that I know
Its the energy level where the probability of finding an electron is 50%, at a given temperature \$T, T\ne0K\$.
Or, Its the highest energy level occupied ...
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What actually (-Delta Q) in the depletion region?
In the semiconductor region (S): a corresponding charge −ΔQ appears, which is distributed in the depletion zone. What is −ΔQ really? I know it is in the semiconductor region, where Xd is the depletion ...
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Steps in Designing using gm/ID Lookup table
I am learning to design circuits using gm/ID lookup tables and I now try to design Miller OTA but I am no sure how to start. I have set myself parameters that I should strife to like: GBW, SR, CL. I ...
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Which electrical components can emulate a current source?
Voltage sources are predominantly found in nature comparing to current sources. However I was wondering which electrical devices made from humans can emulate a current source (very high input ...
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Problem related to semiconductors & E-k graph?
I had found this image in a book, and the graph shows the relationship of E-k. I had studied that E is proportional to k^2 , and k is proportional to the inverse of wavelength. My question is why the ...
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Non-Equilibrium carriers in n-type semiconductor
I got this question in class:
An experiment is conducted as follows for n-Type semiconductor where \$N_D > 10^{16} [cm^{-3}]\$
The semiconductor (at room temperature) is placed in an electric field ...
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Question About GaN Driver Design
I am reading an application note about GaN driver circuit design from Innoscience (Innoscience-AN001¹). Just about capcitor Cc using to provides a negative voltage for gate during turn-off. What ...
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What is the physics behind the silicon diode and the Zener diode?
Zener diode, in reverse has the same behaviour as diode.
In reverse, the diode, when reaching Vmax, the diode goes into avalanche effect mode and get destroyed, whereas as for the Zener it is fine. ...
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Die Size and IC Package
I would like to gain a better understanding of IC package lead inductance and on-die capacitance.
For a physically larger IC chip, would the on-die capacitance generally be higher due to the reduced ...
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Diode in FB vs RB confusion
Here’s what I already know, please correct me if I’m wrong. Say we apply a forward bias on a diode. The free electron of an impurity such as Phosphorus or just from Silicon from the N side will jump ...
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directly connecting highly doped metals to the active intrensic region in an LED instead of p and n doped semiconductor layers?
Why are p- and n-doped semiconductor layers essential in an LED structure? What would happen if, instead of using these layers to inject carriers into the active region, we directly connected highly ...
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Why does slope of Fermi level in a semiconductor indicate current?
(I had a fairly expansive question that I wanted to ask here. In the process of articulating the question concisely, I found my answer. It was a revelation to me so I thought to share it here incase ...
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Semiconductor doping - atomic percent of impurity
This is a exercise from a book
Germanium is doped with \$10^{-2}\$ atomic percent of antimony. Assuming
that at room temperature,all antimony atoms are ionized, compute the
electron and hole ...
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Why use 1D simplification to derive semiconductor device behavior? [closed]
My knowledge is at an undergraduate level, I would appreciate it if your reply were mindful of that. It seems like even at prestigious universities, like MIT, Caltech, semiconductor device behaviour ...
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How is \$V_{DSsat}=V_{GS}- V_T\$ in an E-MOSFET?
In an electronics book by R. Boylestad, it is given that for VDG = VDS-VGS if VDS increases, for constant VGS, VGD decreases which means Drain is more positive than Gate and hence reduces the ...
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In an enhancement MOSFET, how is \$V_{DSsat}=V_{GS}-V_T\$?
In an electronics book by Robert Boylestad & Louis Nashelsky (snip above), it is given that for an enhancement-type MOSFET when \$V_{DS}\$ increases (with constant \$V_{GS}\$), \$V_{GD}\$ then ...
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How much of a MOSFET can you strip before it no longer functions?
I'm writing a program / game for fun to simulate N-type and P-type doped semiconductors. The goal is not to be accurate but fun, but accuracy would be nice.
While developing, I was wondering how much ...
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Is This MOS Capacitor Capacitance vs. Surface Potential Graph (Under Varying Temperatures) Physically Accurate?
I’m analyzing the attached graph (which I wrote in Matlab), which shows the capacitance of an MOS capacitor as a function of the surface potential: $$\psi_s$$ for different temperatures. The graph ...
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How to Identify Terminals on a BC108 Transistor and Can I Use BC547 Instead?
I recently purchased an NPN transistor (BC108) for the following circuit. While I can identify the emitter, base, and collector on the circuit diagram, I’m unsure how to identify these terminals on ...
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The behavior of reverse bias on PN junction [closed]
I have a question about the reverse bias pn junction, while applying reverse voltage the material is being exposed to a reverse field results from the battery and we assume that this field is at the ...
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HCPL2531 offset voltage status at opto output
I am testing in a panel with very high motor noise. I want to pass the encoder data through the opto. When I apply the following scheme, my inputs and outputs are as I want.
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Does TFET uses drift mechanism as MOSFET?
I learned that basic mechanisms of MOSFET which are thermonic emission and drift current. In this case, thermionic emission take charge of supply carrier to channel from source region. Drift take ...
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SMD marking code L41 SOT-23-6
Please help me find the part number for the IC with marking "L41" sot-23-6.
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Effect of external voltage on collision time/ Mobility constant
While studying velocity of a electron in a semiconductor under external bias we derived it something like this, $$v_d= a\ \tau + v_t,$$
where \$a\$ is the acceleration from external bias, \$\tau\$ is ...
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calculating the contact potential of a p-n junction with donor energy level?
A p-n junction is such that the acceptor and donor dopant levels are 0.16 eV from the nearest band edge. The doping level on both sides is \${10}^{16} \text{atoms}/\text{cm}^3\$. What is the built-in ...
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What is / how do I find the general ratios of all of the materials used in a cmos chip?
I am doing a life cycle assessment of a CMOS chip. But I am struggling a lot in finding the general ratios or quantities of the materials used in a chip, which is necessary for calculation of ...
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Jump on varistor I/V curve when "passing" through max. leakage current region to max. clamping voltage region?
I'm taking a course on semiconductor physics and another on something like "usage of electronic devices". On both I've come across the I/V curve on a varistor, this is:
I cannot find the ...
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Simple circuit to bypass preamp when battery fails
A guitar has an on-board battery powered pre-amp between the pickups and the output jack. This is great until the battery fails, when it goes dead until the battery is replaced.
I would like to have a ...
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Noise in classical quantum transmission
In classical quantum transmission, we introduced a scattering model that includes two components: free projection and collision
Now, in this figure, this model is introduced that when it goes up in ...
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Series connection of diode and resistor. Why is there a constant voltage across the diode?
So I know that a diode can be described using the Shockley equation and after a certain voltage, the diode current begins to increase rapidly. The nominal 0.7 volts. I also know that this voltage ...
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How do you justify energy band bending in an unbiased MOS Capacitor?
Here is a MOS Capacitor:
(Image source: Chapter 5 of Modern Semiconductor Devices for Integrated Circuits by Dr. Chenming Hu)
Now lets consider the idea that the gate voltage is held at 0V, just like ...
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Carrier concentrations versus temperature and doping in Matlab
I am currently self studying structure of semi-conductors and I would like to make a graph in Matlab of the number of carriers as a function of temperature and doping. Let's say that I am testing ...
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Diffusion Current for Non-Linear Charge Carrier Configurations
Diffusion current in a MOSFET device can be calculated using Fick's Law per \$J=-qD\frac{d \rho}{dx}\$. It is often taken that the charge carrier configuration (\$\rho\$) across the MOSFET channel is ...
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Where is the flaw in this transistor, FET, Diode design?
I'm a hobbyist and I've designed and built (fabbed a small circuit board, schematic attached) a circuit to power a brushless DC motor using a solar panel which also charges a stand-by battery and ...
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What is a precise definiton of "cut-in" voltage as applied to diodes?
What is the "cut-in" voltage or knee voltage of a diode or transistor?
In a lot of books I read that the cut-in or knee voltage of a diode (or transistor) is when the diode starts conducting ...
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Semiconductor device testing [closed]
I'm a graduate engineer who's recently started a job testing silicon wafers consisting of both power MOSFETs or diodes and some IGBTs.
Unfortunately there's little in terms of support and training ...
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Electron holes and negatively charged particles [closed]
I'm studying BJTs and have a kind of legacy question. Is there any relation with electron holes and the positive charged point charges you'd see in simple Coulomb law applications?
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