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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3answers
668 views

Understanding optocoupler performance with collecor or emitter resistors

When using an optocoupler, is there a difference performance'wise whether using a collector or an emitter resistor? When using a normal transistor the base to emitter voltage gain is approximately 1, ...
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2answers
162 views

Is there a theoretical limit to power supply transformation efficiency?

As I'm looking at some resistive-load applications I'm wondering whether there are any rules that put an upper-limit on supply-matching efficiency. Because if a load isn't matched to the power supply ...
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5answers
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RC differentiator circuit explaination

This is the circuit of a basic RC differentiator, with the input/output voltage waveforms. First of all, I don't understand why there is decrease in the output voltage (discharging of charge from ...
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2answers
44 views

Is symmetrical current perfectly symmetrical beyond analysis? [closed]

Lets suppose that a circuit was constructed with almost identical components and wires to a ridiculous accuracy. When we say that a current is equal due to symmetry after a branch in a node with ...
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2answers
2k views

Does changing the Voltage and the Current passing through an LED affect the result in the same way?

More directly : passing electricity that is 0.5 times the amperage of the one required will make the LED half bright, right? Is it the same with halving its voltage requirement? Or will it not turn on ...
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2answers
256 views

Help with DC circuit theory problem

I need help with this DC circuit problem: When the switch is open, voltage between points A and B is 2V. When the switch is closed, through variable resistor \$R_{p}\$ flows maximum current, and \$R_{...
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4answers
1k views

Voltage and Current along a Wire

In this question I am referring to this article. At first I was looking for a physical explanation of the fact that energy or the signal, respectively, travels much faster through a wire than the ...
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1answer
109 views

How microprossesor perfoms substration by 2's complement

How microprossesor perfoms substration by 2's complement for 5 + (-3) ? I know this might be basic, but to be honest I didn't get it at all. ...
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1answer
169 views

Circuit Impedance

What is the impedance of the following network? My textbook says $$Z = R_i + R + jwL + 1/jwC$$ But I can't seem to make that work.
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1answer
548 views

A way to cancel/or harness back-emf?

In systems where there is back-emf induced to oppose the applied voltage, or to change it in cases of power converters, is there a direct way to cancel back-emf or harness it back? The simplest way ...
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2answers
4k views

finding the gain of a two stage voltage amplifier

i currently do not know how to approach this question, in terms of simplifying the circuit and which formulas to use in order to find the gain
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1answer
68 views

Analysis of the effect a opposing voltage source has to a buck-converter's output?

I have two voltage sources Vps and V1 connected in series: simulate this circuit – Schematic created using CircuitLab There is also Load(1) connected which I believe is in series as well, and ...
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5answers
2k views

Explanation of 2nd order transfer function

I am reading about the 2nd order transfer function of a 2nd order system (like the mass-spring-damper system). I am constantly seeing the following form as the standard one: \begin{equation} H(s) = \...
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1answer
102 views

Why thevinin is applied to voltage source

Why do we use superposition with independent voltage source? and it isn't linear(I mean homogeneity and additivity). EX: independent Voltage source V = 4 volts is not linear(homogeneity and ...
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1answer
343 views

Using superposition to solve circuit with one voltage source and a dependent source

If i use super position to solve a circuit with one voltage source and one current dependent voltage source, does it make sense to use superposition to eliminate the independent voltage source, and do ...
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1answer
154 views

Calculations: Antenna specs; SWR, Bandwidth, Rad.Eff, Q-factor

Is it possible to give approx. answers about what an antenna is capable of? There is a lot of formuals out there, but every single one I found is based on actual measurement; input, output, SWR (...
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7answers
3k views

What makes a circuit digital?

I've been trying to understand how a circuit becomes digital. I understand the different between an analog signal and a digital signal, but I don't see where digital circuits come from if all the ...
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1answer
293 views

What is the software used in this image(semiconductor simulation)?

If I interpret this correctly, this means there is some nice software to simulate various properties of semiconductors. Does anyone know what it is or alternatively what packages do the same thing?
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2answers
4k views

Does perfect insulation exist?

In hydraulics, I think perfect sealing is achievable - it is not science fiction to consider a material whose pores are smaller than a water molecule (or is it?), which would yield zero flow rate. ...
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1answer
98 views

Annoying Biomedical Electrical Engineering Question - How do you relate circuit values to find the distance of the nodes of ranvier?

Question is as follows: I have the electrical circuit drawn as described by the question (ie, the electrical circuit representation of a membrane with Rm1 = 0, Cm1=0 then in series with Rn and a DC ...
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7answers
3k views

Why do LEDs have a maximum current?

So I understand that LED's have a maximum current (like 20mA for instance), but scientifically why is this? Using the water analogy it seems like a high voltage would be the thing that would mess up ...
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1answer
330 views

Simple Analogy for Impedance and Load?

Can someone explain what impedance and load really are? I have a textbook in front of me and I have taken and passed the EE class on it, but aside from a textbook definition I can't seem to get a ...
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2answers
92 views

Control: what is the proper justification that you can't just make the output equal to the input if the system produces unstable output

Suppose we have a signal, it goes into the plant and generates an unstable response, a common question then arise at that point is why can't we just set our output to a "hard-coded" input. Think of ...
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3answers
115 views

Simple Theory question about Circuit Analysis

I have the following circuit. I calculated it's transfer function, in the common way, to be: \$ \frac{Vo(s)}{E(s)} = \frac{-R_3}{s\ R_2R_4C + R_2} \$ Then i thought something else. Since there's ...
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2answers
273 views

Why is this a 7th order circuit?

This is the circuit: I saw it in a book. It said that this is a 7th order circuit. From theory we know that the order of linear passive circuits is determined by the sum of capacitors and inductors, ...
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1answer
128 views

Homework: DC circuit help

I need help with the following problem: Find range of resistance R4 and voltage U4 so that the range of current I is $$I \in [-3A,-1A]$$ E=5V, E4=6V, Ig=1A, Ig4=-3A, R1=2ohm, R2=3ohm, ...
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1answer
1k views

Wireless Power Transfer Circuit Theory

I made this circuit, and it is working fine. But didn't understood the theory in it. How is it putting a frequency in the coil? It did not match with any of the oscillator circuits. And also it is not ...
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1answer
3k views

Norton's and Thevenin's theorems importance

Are Norton's and Thevenin's theorems used in real life? And in which situations? I'm reading a circuit analysis book and I asked myself: do electrical engineers use these theorems to get current and ...
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2answers
141 views

Physical changes caused by charge pump

Charge pumps are very cool circuits because they challenge my ideas about how voltage works. I'm very comfortable with the math behind line integrals, so to define "voltage" as the work done to move ...
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4answers
12k views

Why is the Ampere the only SI fundamental unit for electricity?

According to wikipedia the only SI fundamental unit for Matters Electrickal is the ampere. Don't you at least need the ohm to derive anything? How would you make volts from only amps? Perhaps I ...
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1answer
122 views

Channel Coding with Higher modulation

Just had a theoretical question. I'm reading a book on LTE, and I came across an introductory section that talks about using higher modulation with channel coding. I understand that usually using ...
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3answers
436 views

Inductance of toroidal-cylindrical inductor?

If the inductance of a solenoid is \$L_{\text{sol}}=\frac{\mu N^2 A}{l}\$ and the inductance of a toroid is \$L_{\text{tor}}=\frac{\mu N^2 r^2}{D}\$, is it correct to assume that the inductance of a "...
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1answer
83 views

How does cascoding helps

In order to improve the output impedance of a current mirror emitter resistance are added to them..but on the other way these emitter resistances have certain drawbacks which involve restricting ...
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3answers
108 views

Why does output impedance behaves this way

Why does the output impedance(Ro) of a common emitter amplifier is considered in parallel with the collector resistance(Rc)...as according to the KVL--->Vcc=IcRc+Vce+IeRe they seems to be in series......
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2answers
1k views

Why would Z/P cancellation with real part > 0 between the plant and the controller make the system unstable?

Can someone help me verify the claim if there is a zero pole cancellation with real part > 0 between controller Gc and plant Gp, then the system is not stable? I can't find any literature that ...
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2answers
3k views

Working of a current mirror as an active load

Ordinary resistor as load in a transistor amplifier has a certain short coming…we cant have voltage and current gain simultaneously ….. In this circuit a current mirror is actings as an active load ...
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1answer
880 views

Why does Nyquist plot only need loop gain but not the entire closed loop transfer function?

I was trying to compare a Bode plot and a Nyquist plot of the same system and realized that I was probably comparing apples to oranges Bode plot is plotting the entire closed loop transfer function, ...
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5answers
7k views

Why pulsed DC passes through a capacitor?

OK, the current flowing through a capacitor equals C*dV/dt, I'm aware of that. What I don't understand is the physics of the process: why does a capacitor pass pulsed DC (0-10V for example) when ...
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2answers
182 views

current flow to vcc

Hi, i want to build an encoder schematic using zener diode, so the input voltage from encoder can more than 5V (using zener 5.1V), if the input voltage from encoder 0V, voltage to uC is 0V, if the ...
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1answer
223 views

no distortion amp circuit, max. (d(Vout)/dt )max< slew rate, why not (d(Vin)/dt)max?

I think slew rate is how fast a circuit can react to a given input. I was asked to find the frequency limit where the output would show no distortion and tried to find it by (d(Vin)/dt)max < slew ...
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2answers
1k views

high side vs low side load control

Background Fairly standard scenario - I have an inductive load (servo or something similar) that I turn on and off as needed (several times per hour, nothing high frequency). In a scenario where the ...
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2answers
332 views

What are some of the real life example of the so called “tracking and regulation” problem in control theory?

Given a plant, we need to design a controller that takes in an input r and then ensure that steady state error between the output and input goes to zero while the system remains stable. What is a ...
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1answer
457 views

Control theory: What is the physical interpretation of asymptotic stability

For Bounded Input, Bounded Output stability (BIBO), there is a very nice interpretation. All it means is that if for any finite signal the system produces a finite output signal, then the system (...
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2answers
2k views

Can an electric circuit do recursion?

Can an electric circuit do recursion? By recursion I mean any kind of recursion, tail, binary, nested, etc: http://www.sparknotes.com/cs/recursion/whatisrecursion/section2.rhtml By electric circuit ...
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1answer
759 views

How to solve first-order RC circuit?

I've got a question, and I just keep getting myself confused when I try to solve it. The problem asks to find voltage and current and resistor currents transients (the switch is opened at t=0). Before ...
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2answers
879 views

Relaxation oscillator period

For an electronics project I am using a Schmitt Trigger relaxation oscillator. The equation for voltage across a capacitor in time t is $$V_c = V_s(1-e^{\frac{-t}{RC}})$$ My Schmitt Trigger uses a ...
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3answers
931 views

8 bit computer graphics [closed]

I'm working on learning how 8 bit computers work and operate. I know you can make a (tedious) microprocessor with a larg amount of logic gates and such, but how does it read graphics? I know this uses ...
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1answer
4k views

Caculating baud rate of Ethernet per wire

I'm trying to find the answer to what should be a simple question. How do I calculate the physical rate bits are transmitted on an individual Ethernet wire? I am interested specifically in 100 Mbps ...
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1answer
3k views

why ohmic losses increase with resistance?

Electrical newbie here. I'm trying to get understanding how is resistance involved with power dissipation (ohmic losses, eg. heating). Primarily I'm looking at Electromagnet coil, it says the losses ...
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3answers
796 views

How to convert noise to noise density in mic pre amps

I am trying to compare two low noise mic pres for the lowest noise, and I am looking at the TI1012 and MAX9814 MAX9814: ♦ Low Input-Referred Noise Density of 30nV/√Hz TI1012: Output Voltage Noise (...