Questions tagged [circuit-theory]

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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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-2 votes
3 answers
84 views

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
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1 answer
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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 ...
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2 votes
2 answers
1k views

Do higher voltages cause heating?

I'm trying to wrap my head around energy consumption in general. For some background info, I'm an engineering student and am familiar with the usual electrical engineering formulae Here is what caused ...
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1 answer
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How do you prove that a certain circuit is impossible to construct with a certain amount of switches?

I wanted to make a subcircuit, which, if viewed as a black-box, is a two-terminal device, which can behave as a closed circuit (0 Ω) 25 Ω 50 Ω an open circuit (∞ Ω) (sans non-idealities of course; i....
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Is it possible to constrain a circuit's voltage supply to a specific voltage range?

I have a circuit which requires exactly 12v to work properly, with a maximum tolerance of ±0.5V. The circuit is arbitrary and one can think of it as a theoretical question, but let's say that it ...
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-1 votes
1 answer
102 views

Books on network theory [closed]

I really want to know which books should I read to learn the subject- Network theory in electrical engineering. I know there are some popular books out there in the market, but I will really ...
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5 votes
3 answers
236 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}{\...
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Why reactive components have less influence at low frequencies?

Some textbooks state that reactive components (may) have less influence at low frequencies, since inductance and capacitance are generally more significant at hifh freqs. "Pratical electronics ...
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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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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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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 ...
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NgSpice transient analysis on BJT Colpitts oscillator

Can you tell me how can I run a transient analysis on it? What I am curious about is the startup process. I'd use a simple textbook example BJT circuit, the point is on the simulation setup/commands. ...
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3 votes
1 answer
207 views

Clarifying an article on switch debouncing - something about leakage current causing trouble

I recently read this article on switch debouncing: A Guide to Debouncing - Part 2, or, How to Debounce a Contact in Two Easy Pages, by Jack Ganssle. The article is on choosing the correct resistor and ...
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76 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 ...
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1 answer
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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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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 ...
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1 answer
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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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1 vote
0 answers
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Multipole Network Power Calculation

How do we calculate the DC power consumption of a multipole resistive network, if we know the currents of all the poles (pins) and all the voltages between the poles? Let's say for example, that we ...
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1 vote
1 answer
337 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)}{...
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1 vote
1 answer
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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 ...
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1 vote
2 answers
543 views

dependent current source polarity

In this question, I apply the current cycle law, I find the current i1 to 25uA. I find the voltage on the dependent current source -2 volts. When I go through the formulas, there is no problem here. ...
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2 votes
2 answers
116 views

Transient solution of current in circuit with two coupled inductors, with resistances

Circuit in question is given below. I want to find why I can not get the same current waveform as PSpice gives me. Basically I want to calculate formula for i1(t) by hand and get something as close ...
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3 votes
1 answer
248 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 ...
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1 answer
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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 &...
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1 vote
4 answers
107 views

Energy Transport in Circuits

I've been reading about how energy is actually transported in circuits (I first read about it here: http://amasci.com/miscon/ener1.html). The description in this article of why electrons don't move ...
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2 votes
4 answers
145 views

Relation between transmission line and 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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2 votes
1 answer
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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. ...
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3 votes
1 answer
53 views

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 ...
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  • 499
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1 answer
945 views

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 ...
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3 answers
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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 ...
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1 vote
1 answer
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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 ...
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2 answers
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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 ...
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1 answer
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Initial Condition in Series RLC Circuit

I have the following RCL circuit simulate this circuit – Schematic created using CircuitLab After using the Laplace transform my lecture notes mention that we get the following circuit ...
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1 answer
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Current going into the positive pole of a battery while discharging a capacitor

Please bear with me if this is a fundamental question. Let's suppose we have an RC circuit, charging a capacitor up to the voltage of a battery of 9V. The capacitor is currently at 9V, we switch the ...
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0 votes
1 answer
81 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 ...
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0 votes
3 answers
815 views

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 ...
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  • 3,246
0 votes
1 answer
83 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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0 votes
2 answers
481 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 ...
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0 votes
1 answer
37 views

Audio jack adaptor [closed]

Can I connect two headphone to each other using a female to female connector and setup communication between the headphones?
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2 votes
0 answers
65 views

Why is any general cutset equation a linear combination of fundamental cutsets?

I have currently started studying circuit theory and my professor introduced graphs to form kvl and kcl equations. When we form the cutset matrix using fundamental cutsets it is easy to understand ...
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0 answers
40 views

Current flow on this branch [duplicate]

What happens in this current branch? In circuit analysis how to deal with branches like this?
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0 votes
1 answer
40 views

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?
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0 votes
1 answer
142 views

NMOS High Side switch circuit solving

I'm trying to get my head around the circuit theory behind the high side NMOS switch, here is the shematics: My question is not about whether this is a good or a bad way to make a high side switch (I ...
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3 answers
746 views

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 ...
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1 answer
179 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 ...
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2 votes
1 answer
1k 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 ...
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2 answers
195 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 ...
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1 vote
1 answer
3k views

mesh analysis with current sources + dependent current source

I need to find Ix with mesh analysis method. I will really appreciate your help. So, I turned Is2 to a voltage source and tried writing equations for a super mesh and KCL. anyway, I miss something in ...
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2 answers
144 views

What are the initial conditions used to find the coefficients in the current equations?

Suppose a RLC series circuit. R, L and C are in series with a battery and a switch. The switch is open. L and C are discharged. At t=0, the switch is closed and the battery (V1) feeds the circuit. I ...
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