All Questions
Tagged with circuit-theory circuit-analysis
64 questions
0
votes
4
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130
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Can we solve all linear circuits using only KVL and constitutive relations?
Can We Solve for Node Voltages and Branch Currents in Any Linear Circuit Using Only KVL and Constitutive Relations?
In circuits with a single loop, it's trivial to solve using only Kirchhoff's Voltage ...
1
vote
1
answer
90
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Does KVL guarantee identical voltages/currents in similar circuits?
I have a question that is a bit abstract. Assuming I have two proper linear circuits, A and B, which have:
The same ideal components (for example, voltage source, inductor, capacitor, resistor)
The ...
0
votes
2
answers
163
views
IV curve arithmetic - reference request
When playing around with electrical concepts in my head, I realized that the IV characteristic of any combination of elements, in series or in parallel, can be computed by simply adding the IV curves ...
1
vote
1
answer
59
views
Computing input resistance of two common-base configurations
When computing the input resistance of this common base configuration, the collector current \$I_C\$ is approximated as equal to the emitter current \$I_E\$:
simulate this circuit – Schematic ...
0
votes
2
answers
278
views
How to find a missing resistor?
This seems to be a really simple question. I'm not really sure where I went wrong in my solution. Please forgive me if this seems irritatingly simple, I've only just started learning about electric ...
1
vote
1
answer
291
views
How to simplify this complex DC circuit?
I find it very hard to simplify this circuit. Currently practicing for my removal exam and this was one of the problems I failed on one of my previous exams.
Especially the middle part makes me so ...
2
votes
2
answers
122
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Good way to obtain voltages along (non-uniform) \$RC\$ line
I have a long RC line, e.g.:
simulate this circuit – Schematic created using CircuitLab
Is there a good way to obtain the voltages on nodes V1, ..., Vn (possibly approximated) at a specific ...
1
vote
4
answers
767
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Synthesizing an impedance given by transfer function (poles/zeros) using a passive network
I would like to synthesize an arbitrary passive network based on a given transfer function (poles/zeros).
The origin is the output impedance of a voltage regulator for which I want to find an ...
-2
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3
answers
546
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How do I use Norton's Theorem to find the current in this resistor? [closed]
I've been trying to solve this question but it seems impossible
0
votes
1
answer
308
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Mesh Current Method and Analysis DC
This is my approach so far:
simulate this circuit – Schematic created using CircuitLab
I'm having problems with the third loop, only because of the fact that there are two batteries that are ...
6
votes
3
answers
624
views
Is reactive power periodic in nature? What is the exact difference between active power, average power, and real power?
Consider an RC circuit which is supplied by a sine source
$$v(t)=V_m\cdot \sin(\omega t)$$
The current through the circuit will be
$$i(t)=I_m\cdot \sin(\omega t+\phi) \\
\phi=\arctan \left(\dfrac{1}{\...
2
votes
1
answer
185
views
How to analytically find node voltages in a voltage doubler?
Given a voltage doubler circuit:
simulate this circuit – Schematic created using CircuitLab
You can figure out what should happen in stead state if \$R_L=\infty\$ and \$R_s=0\$. In that case, \$...
1
vote
1
answer
358
views
Meaning of the determinant of an ABCD transmission matrix
In a thesis, [1] I found the following statement:
To determine [characteristic impedance and] dispersion relationships for
an arbitrary reciprocal network having the transmission matrix
$$ \begin{...
2
votes
2
answers
121
views
Why losslessness requires voltage and current must be both zero?
In the textbook (pg. 260 Linear Circuit Analysis, by Artice Davis), losslessness is defined in such way:
Losslessness: If w(\$\infty\$) = 0 for any v(t) and i(t) waveforms supported by the
element ...
0
votes
0
answers
146
views
Understanding MOSFET operating transitions
I'm trying to conceptually understand the output voltage and the operating condition transitions that the MOSFETs in the circuit below go through as the input voltage is swept from 0 to VDD.
It's not ...
0
votes
0
answers
221
views
Causes for negative port resistance of passive device (or obtaining |S11|>0 from measurements)
Suppose you have two reciprocal (passive) devices, A and B, both described with S-parameters \$S_a\$ and \$S_b\$. With a VNA, you measure \$S_a\$ and \$S_{\rm tot}\$ (S-parameters of AB, both devices ...
1
vote
1
answer
612
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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....
1
vote
1
answer
1k
views
Transfer function and characteristic equation
I have the following network (page 805, example 14.5, Agarwal & Lang, Foundations of Analog and Digital Circuits):
The associated transfer function for \$i_z, v_z\$ is \$ H(s) = \frac{I_z (s)}{...
1
vote
1
answer
221
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Complex impedances of capacitors/inductors in the phasor domain
I'm trying to verify the complex impedances of passive components in the phasor domain (not s-domain). Take for example the inductor, whose element law is \$ v = L \frac{di}{dt} \$. Assuming a complex ...
3
votes
1
answer
647
views
Why is this two-inductor circuit first order?
I have the following circuit with two inductors. Apparently this is a first order circuit (judging from my solutions for \$ i_1, i_2\$; and circuit simulations) but it's not intuitively clear to me ...
0
votes
1
answer
234
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Confusion Between Dual Capacitor/Inductor Circuits
I'm trying to physically understand the responses of this pair of (dual) circuits: a step current source driving a capacitor and a step voltage source driving an inductor.
simulate this circuit &...
2
votes
1
answer
93
views
Maximum error of nominal resistor combinations
Suppose you have resistors which have nominal values of \$R_0\$ or \$2R_0\$ but can vary to be anywhere between \$(1 ± .03)R_0\$ or \$(2 ± .06)R_0\$, respectively, so each can have about 3% error.
...
4
votes
1
answer
156
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Linear Circuit and System Interpetation
My question is about interpreting a given circuit as being itself a linear system. We know that a linear system needs to satisfy the superposition principle: if \$f(ax_1+bx_2)=af(x_1)+bf(x_2)\$. This ...
1
vote
1
answer
2k
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Capacitor sign convention
I am a lot confused about how to assign the current of a capacitor and the sign of its constitutive relation, because usually in physics and in engineering there are different conventions. There are ...
0
votes
3
answers
664
views
Why should signals in circuits propagate much slower than the speed of light?
I've read a couple of other topics (such as this one and this one) about the lumped circuit abstraction requiring that signal timescales (i.e. the period of the highest frequency signal component) be ...
1
vote
1
answer
588
views
Norton Equivalent and current convention
Consider that we are trying to find the Norton equivalent of a certain circuit . According to my understanding , while finding the short circuit current or the Norton current , we should point it ...
0
votes
2
answers
84
views
Equivalent circuit with voltage buffer
let's consider this circuit:
Consider the node A: it is at GND (0 V) because of the voltage buffer at right.
So my question is: is it possible to remove it and to consider the following simplified ...
0
votes
1
answer
136
views
Electric Power in Frequency Domain
Let's consider an impedance Z inside a certain circuit. Let's suppose that we are working with a generic non periodic signal (so it is possible to analyze the circuit with the Fourier Transform).
How ...
0
votes
3
answers
2k
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Dissipation and Impedance
it is known that power losses (which become heat) in circuits are due to resistances, because of Joule Effect. But sometimes I read that dissipation is due to the real part of a certain impedance, and ...
0
votes
2
answers
1k
views
Current Source and Short Circuit
let's consider this circuit:
How can I analyze it? Which is the expression of the current in the short circuit? Is it correct to split the circuit in the following way (I always did it when there was ...
0
votes
0
answers
41
views
Current flow on this branch [duplicate]
What happens in this current branch? In circuit analysis how to deal with branches like this?
0
votes
1
answer
105
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What is the contribution of dependent sources while calculating the Thevenin’s Voltage?
I was solving a problem and while calculating the Thevenin’s voltage the dependent voltage source contribution was not taken into account.Why?What important concept am I missing?
0
votes
3
answers
1k
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How does one relate an RC circuit's time domain solution to phasors?
It seems to be a given for phasor analysis that the voltage across a capacitor can be defined as follows:
$$ V_{C}(t) = V_{A}\cos(\omega t + \phi)\tag{1} $$
Where Vc(t) is the capacitor's voltage at ...
0
votes
1
answer
228
views
Determining the Thevenin Equivalent
How could I proceed with this circuit to determine the Thevenin Equivalent? I have the values of \$R_1, R_2, R_3, I_2\$ and the time value for g. I first tried to figure out the total voltage for the ...
2
votes
1
answer
2k
views
Why the opposite of the passive sign convention is not the active sign convention?
Studying the fundamentals of circuit theory, I was reading the Wikipedia article on the Passive Sign Convention and found out about the Active Sign Convention (ASC). After searching many introductory ...
0
votes
2
answers
278
views
How is voltage divided between two reverse-biased ideal diodes?
Suppose we have two identical ideal diodes (without any resistance or voltage drop). We connect these two diodes in series, in the same direction, and reverse-bias them with voltage V. Now we have two ...
7
votes
3
answers
3k
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How do I really calculate these resistors?
I am learning about it.
I would like to focus on this circuit
I am trying to calculate R10 and R11.
I want Ic = 10 mA. Transistor is 2N2222A.
This is an amplifier. If I understood how amplifiers ...
3
votes
3
answers
2k
views
How to find the value of alpha in this curcuit?
I have tried to solve this way but i am not sure how to proceed from here:
[![tried solution][2]][2]
1
vote
3
answers
1k
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How to find current in this circuit passing through 4ohm resistor
Below I have added my solution after the question so please let me know how I can solve it after the last step:
These steps to follow to solve the question from where i left in my post ,
FYI :As ...
0
votes
3
answers
137
views
Would a diode with a different forward voltage and response time cause this circuit to behave erratically?
I accidentally substituted diode RS1BB-13-F for S1BB-13-F.
RS1BB-13-F's forward voltage is 1.3V, while S1BB-13-F is 1.1V.
These substitutions were at D8 and D9 in the schematic (top right corner).
...
0
votes
1
answer
486
views
Why are MOSFETs used on the battery gauge lines?
This is from the iPhone 10, previous models didn’t have MOSFETs on the gauge lines so I’m wondering why they’re used now.
Is it so the phone can’t boot with just a voltage present from external ...
0
votes
0
answers
80
views
Are GPIO outputs software or hardware controlled?
I’m trying to diagnose an iPhone 6s that’s stuck in a boot loop. iTunes error points to a baseband issue.
So I’ve compared to a known working board and found that the PMU_TO_BB_PMIC_RESET_L line (at ...
0
votes
4
answers
6k
views
Definition for self-commutated switches
PSIM (an electronic circuit simulation software package) classifies GTO, IGBT, MOSFET as self-commutated switches. However, I ...
0
votes
1
answer
50
views
Nodal Analysis #2 - Where is my mistake?
I am given a problem with its shallow solution (i.e. not all steps/formulas shown). When I tackled the problem (below), my answer didn't match the apparently correct solution. Where is my mistake? The ...
0
votes
0
answers
65
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Nodal Analysis #1 - Where is my mistake?
I am given a problem with its shallow solution (i.e. not all steps/formulas shown). When I tackled the problem (below), my answer didn't match the apparently correct solution. Where is my mistake? The ...
0
votes
1
answer
82
views
Oscillator circuit operation confusion
In this circuit and explanation, it all makes sense except I'm having a hard time picturing Q2 not turning on until C1 has discharged first.
When C1 is discharging through Q1 why doesn't Q2 turn on ...
8
votes
1
answer
11k
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Meaning of Sigma in Laplace transform
I found the question below in a forum and I also have same problem. Unfortunately, there is no answer at all so I will post it here hope someone could make it clear.
A gain relation in a circuit of ...
0
votes
2
answers
157
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Basic circuit analysis - phase shifting
For the part of the circuit of sinusoidal circuit given below, the following data is given (effective values): $$E=10V,I_g=2\sqrt 3 A,I_2=2A.$$
Impedance of conductor is $$Z_C=5\Omega.$$
Current Ig ...
0
votes
2
answers
200
views
Anyone an expert on mobile LCD displays? [closed]
Reason I ask is, I've noticed with water damaged iPhone 6 screens if the pins on the connectors of the screen itself have corroded and you fix them with cleaning and fresh solder or jumper wires 8 out ...
-3
votes
1
answer
107
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Flow of electricity. Need explanation [closed]
simulate this circuit – Schematic created using CircuitLab
People are taught how to calculate this very simple thing, and the calculation goes from source plus to minus, and the diode is there ...