# 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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### 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 ...
210 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 ...
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 ...
301 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 ...
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 ...
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 ...
443 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 (...
726 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 ...
742 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 ...
751 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 ...
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 ...
3k 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. ...
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 ...
685 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 (...
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 ...
110 views

### In adaptive signal processing, what does it mean for an arrow to go through a block?

For example, in this case the FIR digital filter has an arrow going through it. This is common in the signal processing comunity but very unintuitive from a control perspective i.e. where is the arrow ...
109 views

### AC Analysis Mindset [closed]

I'm just trying to solidify my foundational knowledge of ac analysis. So when approached with a basic circuit, lets say a RLC circuit, should my first instinct be to convert each group of components ...
235 views

### Help understanding the function of my circuit. (Bug swatter)

The important thing is the image below. I want to know how it works. Here's what I understand so far. First I'll identify the pieces: -The blue "packet" is a capacitor. Its a $0.030 \mu F$ with ...
470 views

### Op amp has a biased output

I'm designing an op amp circuit to amplify 20mV, 18kHz square wave up to measurable levels (~2-3V). Why is the output signal: Biased at ~400mV Triangular (high output capacitance? is that a thing?) ? ...
20k views

### Why do microcontrollers have so little RAM?

Maybe this is more of a perceptional problem, but it seems like microcontrollers have advanced by leaps and bounds in the last 20 years, in almost all regards, higher clock speed, more peripherals, ...
11k views

### Magnet that needs power to turn off? Inverse coil?

I have never heard of such thing. But it would really suit my needs. I'm inventing a device and during it's operation, it should be able to catch an iron object any time (with a permanent magnet). ...
1k views

### What would happen if an ideal voltage source was connected to an ideal wire?

I've seen it mentioned in discussion that an ideal wire doesn't exist (all wires have resistance), but even if it did, an ideal voltage source doesn't exist (all batteries have internal resistance); ...
971 views

### What is the difference between the substitution principle and Thevenin theorem?

The substitution principle (as seen in this book; in italian, sorry) Let A and B be any two part of an electrical network with voltage and current sources and only resistances, connected by ...
489 views

### Why don't infinitely many sinusoidals exist in an oscillator circuit?

A sinusoidal oscillator, takes the ambient thermal noise or any imbalance in the circuit as input and gives out an oscillation. This kind of oscillators are called to be linear. By the nature of a ...
190 views

### When is it theoretically possible to fit PCB circuit on x Layers (emphasis: x =1)

When is it theoretically possible to fit a given circuit on a certain number of layers? (Presumably PCB layers.) What is/are the name of the mathematics/algorithms that might determine this, or ...
20k views

### Theory question about “j” imaginary unit (AC circuit analysis)

I have just started to learn about AC network analysis and have some questions about "j" (or "i" on my calculator), the imaginary unit. My book doesn't go into a great deal about this, and jumps ...
1k views

### Why do op-amps keep amplifying?

I was reading an old copy of Horowitz and Hill's The Art of Electronics and I am trying to wrap my head around operational amplifiers in negative feedback circuits. As the book explains, as the op-...
232 views

### Would it be practical to build a chip that can do this math?

I was theorizing a new kind of 64-bit number for use in data storage, but then started wondering if it could become practical if created in hardware. (I believe it would be too slow if only software ...
165 views

### Why doesn't linear resistance scale proportionally with the square of length?

I have an in depth question about basic proportionality of resistance. Why doesn't it scale with the square of length? I ask this because what is causing the potential difference on two leads is ...
59 views

### Absolute and relative permitivitty

Principles of Electronic Materials and Devices - Hasap, pg: 585, he says: $$\epsilon_r = \frac{Q}{Q_0} = \frac{C}{C_0} = \text{relative permittivitty}$$ Then he says: It is important to remember ...
7k views

### Induced dipole moment and 'electronic polarization'

Principles of Electronic Materials and Devices - Hasap, pg: 586, he says: The induced dipole moment depends on the electric field causing it. We define a quantity called the polarizability a to ...
9k views

### Is there a maximum possible voltage?

This question got me to wondering if there is a maximum theoretical voltage. It seems to me there's a limit to how much positive or negative charge you could have--say, a container full of electrons ...
575 views

### Design vs reality and what to do when they differ

I've been trying to focus a bit more on Analog circuits lately and found that my design and actual results often don't match up exactly. An example is a Pierce oscillator I built a while back, the ...
5k views

### How can the SI unit of resistivity [Ωm] be interpreted?

The way I interpret the resistance $R$ of a resistor, which has dimensions $[\frac{\mathrm{V}}{\mathrm{A}}]$ is: how many volts must be applied across the resistor to achieve 1 ampere of current?...
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 ...
136 views

### Am I doing this right? (LED's to music)

simulate this circuit – Schematic created using CircuitLab I have been charged with designing and making a circuit that makes LEDs brighten or dim to an audio source. At the time I thought I ...
389 views

### Resistivity and resistance. Permittivity and?

We know that resistance is dependent on both the materials resistivity and the geometry of the material. For a cylindrical or rectangular material the resistance is: $$R=\rho*\frac{l}{A}$$ where l ...
167 views

### At what resistance do I not see a voltage drop across a resistor?

If I have a circuit like this and measure the voltage drop across the resistor I get a value, regardless of what resistor I use: However, if I stick a piece of wood in there instead of the resistor I ...
162 views

### Is it possible to have a continuous quantized signal or a discrete infinite precision signal?

When converting an analog signal to the digital domain I understand that one does two things. An analog signal is continuous and must be sampled in to discrete time segments (Discretization) The ...
25k views

### Where does U for voltage come from?

I believe in Europe the letter U is commonly used for voltage in (eg.) Ohm's law $U = I × R$. I think I understand where the letter V came from, commonly used in North America. But what's the story ...
166 views

### Biological 'Black Box' - how to test for underlying logic?

Firstly, I am a neuroscientist - so bear with me! I have a collection of connected brain cells (network) and a means of recording the electrical output, as well as manipulating the input to the ...
843 views

### What are the technical challenges to store electricity from lightning strikes? [duplicate]

I ask myself that question every time I watch a Tesla documentary. So, let's get some answers down so the smart ones can think about it and we can clean-up our environment. There is free electricity ...
64k views

### When people talk about a device “drawing” current, what do they mean? Why do devices under load “draw” more current?

In my (extremely rudimentary) understanding, the amount of current flowing in a circuit is determined by a) its resistance, and b) the voltage of the power source (voltage from beginning to end), ...
193 views

RF newbie here. Lately I've been experimenting with RF. I built some simple oscillators, managing to get a tank circuit working as well as buffering the 1 megahertz output of a tin can oscillator. ...
753 views

### Series/Parallel DC circuit analysis training issue

I'm blocked in this exercise. I don't get how I can compute R1/R2/R3 voltage. Here's the schema : simulate this circuit – Schematic created using CircuitLab So I was able to calculate some ...
1k views

### Current divider rule calculation issue

I'm doing the exercises from Wisc-Online. This one I think they are really great to learn and practice and have already done a bunch of their practical trainings. But here I'm starting to be crazy. I ...
59k views

### What does common mode voltage stand for in an instrumentation amplifier?

I was reading a text about instrumentation amplifiers. I couldn't find any easy explanation what really common mode voltage means and its importance.
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### How does a domestic appliance “know” how much current to draw?

I have a small wall plug which takes 240V 50Hz AC from the mains, and can give me 500mA 5V DC. I suspect there is a transformer stepping the voltage down and a bridge rectifier converting the AC to DC....