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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Designing a common emitter audio pre-amplifier

I am trying to design and simulate a common emitter audio pre-amplifier using 2N2219 with characteristics based on industry standards (audio frequency response, etc. Corner frequency must be less than ...
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2 answers
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AC voltage and frequency as complex number?

For some software I am writing, I coded classes of electrical systems that receive a voltage and return the current response. For the DC case that's easy: I pass a real number as argument, the voltage,...
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Why BJT thermal voltage can be not equal to kT/q in SPICE3

In SPICE, apart from effects such as basewidth modulation and base-collector leakage the collector current is given by the expression (according to the original SPICE2 PhD work) But actually, ...
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How to show that all power in an RC circuit is delivered to the resistor

I am new to electronics and I've been working my way through the Art of Electronics. I've have been able to complete all the exercises up to this point but I have been struggling on this one. Right ...
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1 vote
3 answers
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Why is my best placement of a directional antenna so weird?

I moved to an offgrid house with a 3G/4G repeater, with a short, enclosed directional antenna. It was wobbling and poorly mounted on an unstable wood plank at the base of a window, so I decided to ...
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2 votes
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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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Transistor analysis with 2 voltage sources

I want to calculate the DC currents of this circuit, and based on the superpostion theorem, I thought of ignoring Vqdc9 first, in order to calulate I2, I21 and I22, as shown in figure 2. After that, I ...
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3 votes
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What is the correct carrier concentration equation to use?

In this book I am reading, it gives the intrinsic carrier concentration as: \$ n_i = \sqrt{N_c\cdot N_v} \cdot e^{({\frac{-E_g}{2*K*T}})} \$ While another book says the carrier concentration is: \$ \...
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Why do we not see multiple or parallel DC PSUs?

A friend mentioned that his home router had blown its 12V PSU recently and had to be replaced. That got me wondering - Servers and routers can have isolated dual PSUs for exactly this condition, but ...
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Is the amplitude of the sum of 2 transmitters of white noise at a given frequency greater than each individual transmission?

If you have two antennas \$T_1\$ and \$T_2\$ each broadcasting 10GHz Gaussian White Noise at the same receiver, each with an EIRP of say 20 dBW with a random phase offset between them, then is there ...
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Why is Line coding called "Line coding"?

Why is line coding also called digital base band modulation named "line coding" where does it come? and how is the name it to modulation
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2 votes
1 answer
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About power dissipation of capacitors and inductors & I-V phase difference

For instance, The Art of Electronics (by Horowitz & Hill) states that ideal capacitors cannot dissipate power, even though current can flow through them, because the voltage and current are 90° ...
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4 answers
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Difference between Message and Signal in Communication Theory [closed]

What is the difference between a message and a signal in Communication Theory? It seems to me that often they coincide, is this always?
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Can someone confirm my derivation of the generalized power law from Practical Electronics, 4th edition?

I dont know how to use LaTeX, so I used Mathcha and took a snip from there.
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2 votes
1 answer
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Matching via sizes to trace widths

Let's say I've determined a trace width (\$t_w\$) for a trace, and now I want to determine the size of a via on that trace. My intuition is that to maintain the same amount of copper as the trace ...
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7 votes
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Why is BMC/k-induction used in RTL formal verification?

One popular approach for proving safety properties in formal verification of RTL designs is a combination of BMC and \$k\$-induction, which appears to stem from "Checking safety properties using ...
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Is there a method to convert a Butterworth response into Chebyshev and Bessel responses?

I wonder if once there is a completed/aproximated a design model of any of the responses mentionated, it can be operated mathematically (or there is a method/recipe) to generate the other responses? ...
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5 votes
2 answers
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How is the slope of the frequency response of an analog active filter defined?

I have seen different types of filters, and different slope values at -20 db, -40, etc. The literature says that the order define the slope, but how? How can it be mathematically justified? For ...
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How/where does a generator + motor dissipate heat?

I've got a mystery that I can't wrap my head around. A generator is generating 1 kW of electric power. The current goes through copper cables to a motor, which is consuming say 950 W of electric power....
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1 answer
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ESP32 Input Voltage Divider, Concept

Thank you for reading. I have read many other voltage divider explanations and calculators on this site as well as the web. My application is using a voltage divider to lower a possible 5 V signal (...
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4 votes
4 answers
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Will the net current drawn by a microcontroller equal the current supplied by it

Purely a theoretical question. Consider a microcontroller whose only job is to turn 1 pin high and in the process the microcontroller supplies I1 current throught the pin. But suppose we have to turn ...
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1 vote
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How to explain the strange results from this circuit (op-amp : differential amplifier?)

I have a differential amplifier. Problem of "gain" of the op-amp or "how it is wired." I have simulated this as a voltage source controlled voltage (VofV.) As a generic amplifer. ...
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-1 votes
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Switching DC battery on ideal choke?

(Google translation). A switch is activated at the instant t = 0 in a series circuit containing a battery of voltage U (ideal) and an inductor L (ideal). I am in doubt with the answers I have found on ...
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Is it possible to implement one 8-way 1-bit multiplexer?

I'm sorry, but shouldn't 8-way have 3 bits in order to traverse every address? Anyway, I have here a problem, and I am not sure if my solution is correct. The problem: Given the boolean expression \...
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1 vote
2 answers
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Is it possible to syntethize this Voltage Transfer Function?

I have the following voltage transfer function: $$ H(s) = \frac {a s^4 + b s^2 + c}{p s^4 + q s^2 + r} $$ Where \$a, b, c, p, q, r\$ are all real constants. The only method I have been taught to ...
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3 votes
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Does the frequency response \$H(j\omega) \$ exist for system with unstable poles?

This question arose from a discussion between me and TimWescott in the comments here. The question is: Does \$H(j\omega) \$ exist for systems with poles in the RHP (unstable poles)? My own answer to ...
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How many newtons are there in one coulomb of charge?

Or, I should have said, how many newtons of force does one coulomb of charge exert? At a distance, presumably, of one meter? Since N/C is supposedly equivalent to V/m? P.S. What are the values for a ...
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0 votes
1 answer
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What does it mean that in a point Α of an electrical field the voltage is -7?

The title. I am really confused. Does it mean that you need to spend 7J of energy to move Q=1C from there to somewhere where V=0, does the Q you move matter? Does it mean you need to spend 7J to move ...
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3 votes
2 answers
105 views

Theory: Can power cables induce AC voltage in human body?

In a demo video (which I unfortunately can't share) a man makes the following setup: Multimeter on 200 V AC settings with one pin in the ground socket of a conventional mains power socket. Right ...
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0 votes
1 answer
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Op-Amp Impdance Question

For the problem shown above since there is no current travelling through the input of the Op-Amp can we assume that the Op-Amp is acting ideally? And using this assumption can we ignore the output ...
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1 vote
1 answer
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How to analytically find node voltages in a voltage doubler?

Given a voltage doubler circuit: simulate this circuit – Schematic created using CircuitLab You can figure out what should happen in stead state if \$R_L=\infty\$ and \$R_s=0\$. In that case, \$...
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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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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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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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1 vote
1 answer
36 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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1 vote
2 answers
360 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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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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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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-2 votes
1 answer
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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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1 vote
1 answer
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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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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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0 votes
1 answer
117 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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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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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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3 votes
3 answers
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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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2 votes
2 answers
95 views

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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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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6 votes
7 answers
2k views

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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5 answers
362 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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