Questions tagged [theory]
Theory is a contemplative and rational type of abstract or generalizing thinking, or the results of such thinking. Depending on the context
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Given the power spectral density, how do I calculate the bandwidth and total power of \$X(t)\$?
Given the PSD (power spectral density), \$S_x(f)\$, of a signal, how do you calculate the bandwidth and total power of \$X(t)\$?
I think I have the bandwidth but how can I get the total power of \$X(t)...
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1answer
46 views
Blocking capacitor causing signal to go low in otherwise working amp/rectifier circuit
I'm making a simple amp > voltage doubler rectifier circuit to drive an lm3916 meter circuit and when simming to choose between JFET, BJT or OpAmp (just for my learning, I'm looking to a Jfet in ...
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Can channel-length modulation coefficient be larger than 1?
Channel-length modulation coefficient lambda is ideally zero or desired to be as small as possible in real case. I haven't come across the case where lambda > 1. But if Ids is very much sensitive ...
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2answers
63 views
Theory Question: Speakers don't work unless I poke soldered points with screwdriver
In case you couldn't tell by the title, I don't really have any idea what I'm doing with electronics. Something happened though, and I am really curious about it. Don't know how to ask it specifically,...
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1answer
30 views
Operative Definitions of Memory in Circuits
I've been studying Memristors (non-ideal) and some related circuits depending on pinched hysteresis of the IV for use in memory. I'm still puzzled by the lack of general framework for what constitutes ...
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61 views
What is Ethernet diff. pair referenced to between connector and magnetics
This is a little bit confusing part. I clearly understand that in ethernet cable fields are coupled between wires of differential pair. On PCB on IC/PHY side it is also known that differential pair ...
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37 views
A circularly polarized EM wave is perfectly absorbed by any interface?
According to the Fresnel equations, the effective reflectivity of an arbitrarily polarized electromagnetic wave is given as:
$$
\Gamma = \frac{\Gamma_p + \Gamma_s}{2} ,
$$
where \$\Gamma_p\$ and \$\...
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1answer
48 views
Parallel LC circuit Q factor inductance role
I'm wondering why Q factor in parallel LCR circuit is proportional of C and inversely proportional to L according to the formula \$Q = R \sqrt{C/L}\$ completely lost here
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1answer
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What are the modern uses of SPI and I2C protocols [closed]
I have been using I2C and SPi for a few years now, but as I begin working with USB, I realize it is much faster. I still see devices with 2 MCUs that could potentially communicate faster with USB, but ...
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1answer
44 views
Meaning of the determinant of an ABCD transmission matrix
In a thesis, [1] I found the following statement:
To determine [characteristic impedance and] dispersion relationships for
an arbitrary reciprocal network having the transmission matrix
$$ \begin{...
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39 views
Algebraic Data Type
I understand the concept of algebraic data types, but I don't see in what context they are useful or when they would be beneficial. When should I consider using them and how are they useful in ...
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1answer
98 views
Diodes and resistors theory
I came across a problem which I cannot calculate by theory.
How does this circuit with diodes and resistors work?
In the above diahram, I can calculate the current simply by subtracting the voltage ...
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1answer
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Early Deadline First (EDF) scheduling in real-time systems feasibility test proof
I am trying to prove Theorem 6.2 on page 127 of the book Real-Time Systems by Jane W. S. Liu:
http://www.cse.hcmut.edu.vn/~thai/books/2000%20_%20Liu-%20Real%20Time%20Systems.pdf
It is based on Early ...
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1answer
88 views
How to deal with a negative resistor in Z parameters of a passive network?
This question is so basic but for some reason I am not seeing it: Assume an arbitrary passive 2-port network having only isotropic materials. This implies S21=S21 and Z12=Z21 (see https://www....
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3answers
465 views
Possible to control a transistor by BC terminals?
I'm thinking about a strange working mode: the CB part is forward biased and trying to control EC current by CB current.
EB is reversed.
May it work?
Transistor is BJT.
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2answers
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Why passive component has better drift characteristics than active components had?
I came across this paragraph in the classic reference Op Amps For Everyone by Ron Mancini where it says on the first page:
Many attempts has been made to make a stable amplifier, but temperature ...
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1answer
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Common emitter amplifier's \$R_C\$ breaks
What happens if the collector resistor breaks (its value goes to infinity) in a textbook example circuit?
I assume that \$ I_C \$ hits zero, \$ U_{CE} \$ decreases until the transistor goes into ...
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Why is power of a signal equal to square of that signal?
Is there any logic as to why the power of a signal \$\mathrm{x(t)}\$ is taken as \$\mathrm{x^2(t)}\$?
I searched everywhere and there's no clue. My professor told: "It's a standard result so shut ...
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Why does triode voltage drop change as a function of grid voltage?
Imagine a thermionic diode connected in series with a resistor \$R\$. The circuit is hooked up to a voltage source \$V\$. The diode conducts a certain current \$I\$ and \$\Delta V_\text{diode}\ + \...
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5answers
229 views
Is it possible to “hash” a circuit board?
I'll preface this by saying I'm a software engineer by trade and have very little EE knowledge.
In the software world, one can take all the bits that make up a file and generate a hash for a file. ...
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1answer
51 views
Applying Thevenin's theorem between 3 points
I'm studying about transistor polarisation and got confused by this application of Thevenin's theorem, can someone please explain why eT is between B and M and why Vcc stayed even though it's not ...
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Type 1 surge protection: parallel or series?
Type 1 surge protection devices (SPDs) are installed at the outside edge of electric service, usually between the power meter and the meter base/socket, and protect the entire house. But how do they ...
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3answers
158 views
Energy Transformation in Flyback Transformers
I am trying to understand how is energy transferred as a current to secondary of flyback transformer. First due to the dot convention and secondary side diode, current will not flow in secondary and ...
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2answers
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Why do I get such high values when calculating the power dissipation of MOSFET in boost-converter circuit?
I'm a hobbist interested in electronics so I don't have any "professional" training on that.
Currently I'm trying to design a boost converter and now I'm stuck at some calculations.
I wonder ...
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Is Gaussian noise equal to white noise?
If noise on a signal is randomly fluctuating in time domain around its mean following a Gaussian normal distribution (Gaussian noise), would this be equivalent to an constant intensity in the ...
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BJT Hre simulation problem
im having problems understanding the behavour of the hybrid parameter hre in the bjt AC model.
im using the pi equivalent circuit to simulate the relation between hre and Ic (Dc value). i am not ...
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3answers
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relation between transmission line & circuit impedance
What is the relation between the impedance of lumped components and the characteristic impedance of transmission lines?
I have noticed that in some cases transmission lines are loaded with lumped ...
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1answer
49 views
Digital regulator for DCM Boost - How does it relate to duty cycle?
I really hope someone can help me here, I'm tearing my hair out trying to bridge the gap between control theory and electronics.
My aim is to control a discontinuous conduction mode boost converter ...
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6answers
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How do computers output a signal without an input? [closed]
I'm curious about how an output pin gets turned on at a low level when there is no input like pressing a button to complete a circuit.
If you program a raspberry pi to turn on and off an LED how does ...
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5answers
451 views
Generalized Power Equation, Ohm's Law and Ohm's Power Loss?
I'll try to state my questions precisely as I can.
I'm a beginner in Electronics and since I have a background in Physical Chemistry and basic Calculus, the book Practical Electronis for Inventors, ...
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3answers
206 views
What exactly does a resistor's tolerance rating mean?
I thought that I had this pretty much figured out over 30 years ago during my initial schooling, but various answers posted to a support forum of a major semiconductor manufacturer(name withheld to ...
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Why are 22pF capacitors so common? [duplicate]
I've noticed that many circuits use 22pF capacitors. For instance, the Arduino uses them to ground the oscillator pins of its AtMega328. Many tutorials call for exactly this value for simple circuits.
...
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Why don't commercial metal detectors clearly distinguish between iron and other metals?
I've read about how metal detectors work, and what I learnt here on EE.SE and other articles, the main principle is that ferrous metal will increase the inductance of the search coil, while non ...
asked Feb 14 '20 at 12:16
Tomáš Zato - Reinstate Monica
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2answers
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Why does lumped discipline not hold as dimension approaches operating signal wavelength?
I'm studying some basic introduction to the lumped matter discipline on my own. I completely understand where the first two constraints come from (i.e. lumped matter can only interact through their ...
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How can I tell if this boost converter is in continuous or dis-cont. mode?
I'm trying to intuitively understand a boost converter, so I've built a variable duty-cycle oscillator circuit that can go from 1kHz to 50kHz and allows me to adjust the duty cycle from 5-95% without ...
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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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Can the 1D wave equation be recreated in a conductive wire?
I am ignorant of EE, but not the wave equation, so bear with me.
The (scalar) wave equation \$d_{tt} - c^2d_{xx} = 0\$ describes the displacement (and velocity) of some medium through space and time....
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2answers
685 views
Can an induction motor be used to generate power?
Induction motors do not have magnets in them, instead the magnetic field the outer coils generate creates electricity, and subsequently magnetic field, in the inner coil. This means those motors need ...
asked Nov 19 '19 at 15:34
Tomáš Zato - Reinstate Monica
9823 gold badges17 silver badges37 bronze badges
3
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1answer
1k views
Why are circuit results different from theorised?
From the following circuit:
I got the following results in comparison to my theorized calculations:
Why were my result different to my calculations?
Here is my calculations:
Equipment used:
...
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Why is RMS used for P=VI (where there are no squares)?
I understand why RMS values are used for
$$P = {\bar{v^2} \over R}$$
because \$\bar{v^2}\$ would be the "MS" so to speak, and then by square rooting we get the "RMS" (\$\sqrt{\bar{v^2}}\$), which ...
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Transistor Analysis
Here is a problem I saw as an example of transistor analysis: (hFE is 50)
simulate this circuit – Schematic created using CircuitLab
The process is simple, the guy assumed that the transistor ...
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1answer
52 views
Isolated circuits: can their reference voltages (GNDs) be at the same potential?
Suppose there are two independent circuits isolated from each other. If they are isolated, the impedance is very high between them (ideally infinite) and there is no current flowing from one to the ...
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3answers
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Why doesn't electricty flow to earth ground when I connect my oscilloscope ground clip to a floating circuit?
There are two concepts I keep reading about that seem to be conflicting each other. Firstly, whenever there's a potential difference between two points, and those points are connected, electric ...
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How can a resistor be given a positive and negative characteristic?
This question is not pertaining to a circuit, but to individual parts itself.
If for any reason, i want to make a resistor have a positive and negative charge on its either ends, what would be the ...
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How to classify power electronics components in 2 main groups?
I'm working on preparing a course about power electronics, and with my basic search conclusions. I thought that if it's possible or acceptable to classify the power electronics components in 2 main ...
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What happens to a computer as it is cooled towards absolute zero?
What happens to the behavior of a conventional circuit using conventional components as it is cooled towards absolute zero?
To make this question more relatable: What would happen as we cool a modern ...
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Bipolar Transistor Inverter Circuit Analysis
I have been trying to understand this question and I'm just not sure what equation to use for the collector current.
I'm not sure if I need to be using an output voltage function of time?
All I have ...
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5answers
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How can I describe and explain SMPS on a very basic level without diving down in heavy maths / EE lingo?
I'm writing a book about repairing electronics. The audience level for the book is "very little knowledge about electronics" and it's mostly about the mindset and mindtools for finding problem sources ...
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Is space division multiplexing really multiplexing?
I don't know much about electronics, but happened upon the Wikipedia article for Multiplexing, which defined it as:
a method by which multiple analog or digital signals are combined into one signal ...
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5answers
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No potential difference between the negative terminal of battery A and positive terminal of battery B?
I know that if you have two batteries, battery A and battery B, and connect the negative terminal of battery A to the positive terminal of battery B, there is no potential difference. If you consider ...
