All Questions
Tagged with semiconductors transistors
118
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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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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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1
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77
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Bipolar Junction Transistor operating modes
If I use a BJT transistor as a switch, the transistor operates in the saturation or cut-off region, not in the active region.
However, some sources use the formula IC = β·IB. However, this formula is ...
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2
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83
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How do P-type transistors conduct current?
Going through a Introduction to Computing Systems by Yale N. Patt and Sanjay J. Patel and currently reading a chapter on MOS transistors. From what I understand, N-type transistors "close" a ...
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1
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104
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Can I calculate beta by using the quiescent point and a voltage divider?
How can I calculate beta with only the data in the image?
Q is the quiescent point. I've tried with the basics Vcc formulas, but since it doesn't provide any value for Vcc I could not proceed.
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200
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Effect of semiconductor doping on threshold voltage
After reading online, I have modeled this as an relation between the threshold voltage and the doping concentration:
For a N-channel MOSFET on a P-type substrate:
$$
V_{T,N} \propto \sqrt{N_{A}}
$$
...
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2
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3
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396
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What exactly happens at the fundamental level if base voltage is higher than collector voltage in CE transistor?
In the first answer to this question, it is stated that:
This happens even if the base and collector are at the same voltage (!). Basically, one way to model a transistor is as the base-emitter diode,...
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111
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When does the transistor reach the stable status when I add resistor to the emitter
simulate this circuit – Schematic created using CircuitLab
If I add resistor R3, which is an emiter resistor, can it change the value of the base voltage? I've learned that the emmiter voltage ...
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54
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What does the interface between lead(s) and the silicon chip look like inside a semiconductor package?
For a leaded semiconductor, like a diode or a transistor, one of the leads is usually the same piece of metal as the copper pad/heat spreader on the back, which is also shorted to one of the junctions ...
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3
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2
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546
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How do the BJT collector and emitter portion compare in terms of size and charge density?
The diagram of a BJT implies that the two p-n junctions are identical. However, I do know that they are not since we cannot connect the transistor the other way around i.e swap emitter and collector, ...
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What does this schematic symbol mean (transistor with two emitters)?
Basically the question is, what it is?
Are those two emitters (meaning that part of semiconductor heavily doped)?
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Is there anywhere I can download BJT Transistor I-V data?
Is there anywhere I can download some current-voltage data for a bipolar junction transistor? (It doesn't matter that much which one.)
To explain further, for a simple BJT circuit we have the ...
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57
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Power dissipation vs. heat dissipation for transistors and diodes
Are these two concept the same or different for semiconductors? Some power MOSFETS have power ratings in the hundreds of watts, and that's way too high for heat loss.
I try to understand 'power ...
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4
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4
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1k
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Relation between collector current and Vce voltage in saturation mode
I have confusion regarding how collector current affects the voltage across collector to emitter in NPN transistor (2N4123).
How do I interpret this graph? Can I say when collector current increases ...
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3
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659
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Potential distribution in MOSFET
Let us assume that an NMOSFET has its source, drain and substrate grounded therefore VDS and VSB=0 V . We apply a gate voltage VGS=2 V and I want to know how this potential is distributed as we move ...
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BJT: definition of "edge of saturation"
The book Sedra/Smith (Microelectronic circuits) tells in chapter 5 the following:
My question: I found no statement on why the EOS is defined by the point where vc < (vb - 0.4V).
Seems like other ...
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What would a theoretical Group II, Group IV Transistor's Properties be? [closed]
This question is for more than a theory.
I would like to disprove that what I'm working on is not a Group II, Group IV transistor.
I know they CAN exist. I don't know why they don't exist or what ...
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2
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192
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MOSFET gate substrate voltage
In a MOSFET the channel is formed between gate and the body it would sense to use gate body voltage to form the channel. Why is gate source voltage used to form the channel?
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300
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Is an NMOS device symmetrical with regard to its D and S pins? [duplicate]
Can D and S be swapped? (Assuming the body is not internally connected to S.)
The structure of a MOSFET is totally symmetric. Even the LTspice simulation shows that it can be swapped.
Does this ...
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2
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751
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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 ...
2
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1
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282
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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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336
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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 ...
6
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4
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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 ?
1
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1
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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. ...
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474
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Is saturation region defined for a "given" collector emitter voltage?
I have seen the traditonal saturation regions graphs (attached). The graph gives the impression that there is a huge region which is saturation region. Shouln't the saturation region be for a "...
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3
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1k
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Does the collector voltage have to be greater than the emitter voltage by few tenths of a volt for an NPN transitor
For an NPN transistor, does the collector voltage have to be greater than the emitter voltage by few tenths of a volt for it to be in active state? If yes what is the reason?
Also it says greater by a ...
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44
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Node Technology in Modern Transistors
i was reading about the new 2nm chip IBM created and through some reading i learned that the "nm" part does not refer to the actual gate length like it did many years ago. Can anyone tell me ...
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4
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3
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640
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Need to increase the amplitude of op-amp output
I'm using this circuit to measure the RPM of a DISC rotating at 24000 rpm. This circuit is working fine. But the problem is with amplitude. It should be of 4.2V, but actually is of 2V as shown in ...
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149
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Is this question wrong? possible to calculate gain without beta or Ic given? [closed]
How to proceed with this question? I can't think from where to start.
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67
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How temperature difference does not affect transistors in CPUs?
Recently I learned about semi-conductors and some devices.
Today I watched a video on youtube about a guy overclocking a cpu to 7.0 ghz, while cooling it with liquid nitrogen to -192 celsius degrees. ...
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1
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110
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Qualitative explaination of Output Characteristic of Transistor (BJT) using Depletion layer between Collector and Base
From my understanding,
The diffusion layer at a p-n junction is an equilibrium of two opposing forces on charge carriers due to 2 forces - Concentration Gradient and Electric Field caused by Bias and ...
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2
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120
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Transistor: Getting “incorrect” graph for input voltage to output voltage
I tried drawing the graph of \$v_o\$ vs \$v_i\$ for a bipolar junction transistor. I used the below setup (common emitter:)
By design of how the base is a small part compared to others, \$I_b <<...
6
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1
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303
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How point-contact transistor work?
In December 1947 Bardeen, Brattain and Shockey introduced a device which is considered to be the first transistor. This transistor was point-contact device. So, it used metal-semiconductor junctions.
...
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3
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182
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Which semiconductors are good candidates for constructing a CPU? [closed]
Wikipedia offers an excellent list of semiconductor materials but does not include which can be used to create integrated circuits or even logic transistors (PNP or NPN). The Integrated Circuit page ...
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991
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BJT Active Region - Biasing of BE and BC junction
I am having trouble understanding why the BC junction is considered to be reversed biased in these two models. The way I see it, the base looks to be in a higher potential than the collector junction ...
user263783
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3
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165
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Dependency of Collector current in common base transistor(active region)
I just started reading about transistors from book "Microelectronics circuits"by Sedra/Smith,
This is written in book which I don't understand, any help would be much appreciated
For forward ...
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2k
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Gate leakage current for a JFET?
I'm really confused about how JFETs work. JFETS are usually significantly higher doped donor xor acceptor atoms.
My professor mentioned that MOSFETs usually have an oxide in between the the metal and ...
0
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0
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307
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Why do electrons and holes in the base have to recombine in order to create the base current
Khan academy link
In the video above, it is said, that in order for the base current to appear, electrons have to recombine with the holes in the base region.
Why can't they simply go to the base ...
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110
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Iellegible JFET name, seems to be HEPxxxxx
I have this poor scanned schematic on which there is a Motorola P-channel JFET, labeled as Q5, and I can't read the name. It seems to me that the 2nd note is written "Q5 is HEP*1036" where * ...
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5
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156
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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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492
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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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2
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3k
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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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Emitter current and Early effect
I know that due to Early effect in a npn transistor the effective base width reduces.However I can't understand how this will lead to an increase in emitter current.
Some sources say that the charge ...
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2k
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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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175
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PN Junction paradox or something else? [duplicate]
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2
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534
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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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203
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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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1
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202
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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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108
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Semiconductor common emitter configuration
Please could anybody explain the CE configuration, the graphs of \$I_b\$ vs. \$V_{be}\$ and \$I_c\$ vs. \$V_{ce}\$. I can't understand which current remains fixed and how can one regulate \$V_{ce}\$ ...
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Is it misleading to say "holes in semiconductors jump to the other side"? [duplicate]
I'm getting a little confused with the convention of saying that "holes in a semiconductor will move from p-side to n-side and electrons will move the opposite way". I have no trouble with the concept ...
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