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22 votes

What is the physical meaning of negative resistance?

There are a number of mechanisms that result in a region where locally increasing voltage results in locally decreasing current. For example, an Esaki (tunnel) diode. A common example would be a ...
Spehro Pefhany's user avatar
20 votes

LTspice: simulating the bounce effect of a push button

You can use the rand() function to generate a noise-like signal, that combined with time and a bit of math and logic operators can produce something like switch bounce when used to control a ...
GodJihyo's user avatar
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15 votes
Accepted

LTspice: simulating the bounce effect of a push button

I'd suggest using a PWL voltage source. Convert that graph into a .txt file of time vs. voltage level, as accurate as needed. Then set the voltage source to use that PWL file as input. If you need ...
rdtsc's user avatar
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14 votes
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Why is the voltage divider formula used in this circuit to find the terminal voltage?

You are right that we can use Ohm's law. Look at the math: The current in this series circuit is: $$I = \frac{V_1}{R_1+R_2} $$ And the voltage drop across \$R_2\$ is equal to: $$V_{R_2} = I \...
G36's user avatar
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13 votes
Accepted

I don't understand current source, voltage source, infinite resistance, zero resistance etc

If something has infinite resistance wouldn't nothing happen because everything is blocked? I also don't understand what an "open circuit" really means (to my eye it just looks like a ...
DKNguyen's user avatar
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12 votes

LTspice dependent voltage sources circuit

Oh, cripes. I can't believe the answers. Here. Hit F2, find "bv", drop it on the schematic, fill out the formula, hook it up somewhere. Done. Doesn't even have to be grounded. You can stick it ...
jonk's user avatar
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11 votes
Accepted

Why do I get two different answers for the current through the 47 kΩ resistor when I do a source transformation?

If you transform a source and a resistor then the only equivalence is the V/I characteristics at the two terminals of the transformed circuit, not for the elements inside the transformed circuit. If ...
Elliot Alderson's user avatar
10 votes

Why do I get two different answers for the current through the 47 kΩ resistor when I do a source transformation?

I gather you find the correct answer from this transformation: simulate this circuit – Schematic created using CircuitLab One way to see why is that the transformation on the left side doesn't ...
jonk's user avatar
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10 votes
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Practical example of controlled voltage and current sources

Short answer The difference between the ordinary constant sources and dependent sources is that the former have only output (the input is implicit, constant) while the latter have both input and ...
Circuit fantasist's user avatar
9 votes
Accepted

How does one know that the current is flowing downwards through the \$8 \ \Omega\$ resistor?

No, the authors have not declared that the current \$i_8\$ is flowing downward. They have defined some current named \$i_8\$ that is flowing downward. Once the circuit is solved it may be found that ...
Elliot Alderson's user avatar
9 votes

Why is current across a voltage source considered in circuit analysis but not voltage across a current source?

I'm not sure why you think KCL concerns itself with voltages anywhere, or KVL somehow needs to know anything about current anywhere. When applying KCL, we consider only current. When applying KVL, we ...
Simon Fitch's user avatar
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8 votes
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USB C Power delivery doesnt work properly

Most modern USB devices would like to communicate with the power supply to get more than 5V. With USB Type-C, USB-PD communication can be used, but there are also other methods. Your design does not ...
Justme's user avatar
  • 154k
8 votes

Ideal voltage vs ideal current source - which one wins?

Ideal voltage vs ideal current source - which one wins? An ideal voltage source has zero output impedance. An ideal current source has infinite impedance. So, if you connect both in parallel, they do ...
Kuba hasn't forgotten Monica's user avatar
7 votes

Simple way to boost from 24V to 24.8V? (up to 10A)

Ah. So you're driving LEDs directly with voltage, and the units you've got work best at 24.8 volts. Congratulations - you're about to kill your LEDs. The reason that the manufacturer's specs are not ...
WhatRoughBeast's user avatar
7 votes
Accepted

Don't individual signal sources affect each other when using a summing amplifier?

I cannot intuitively see why this circuit works. Consider a somewhat ideal op-amp with an open loop gain of (say) 100,000. Consider next that the output voltage at any point in time is not saturated ...
Andy aka's user avatar
  • 462k
7 votes

Why is the voltage divider formula used in this circuit to find the terminal voltage?

You can calculate it using Ohm's law by applying it twice: once to R1+R2 to find the current in the entire circuit, then again to find the voltage across R2. But it's much faster if you know the ...
DKNguyen's user avatar
  • 56.8k
7 votes
Accepted

Can power outlet be taken as a current source?

Both 'current source' and 'voltage source' as presented in your course in electronics are idealisations. They are theoretical entities we never meet in practice. But they are often good approximations ...
Neil_UK's user avatar
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7 votes

What does a voltage or current source actually output?

There are only two quantities that can be considered fundamental, or "real", in the sense that they actually exist, and those are voltage and current. Resistance is artificial, a contrived ...
Simon Fitch's user avatar
  • 37.6k
7 votes

What does a voltage or current source actually output?

Voltage is the cause, current is the effect. So both sources provide a voltage on their terminals. In the voltage source the voltage on the output terminals has, or is intended to have, a constant ...
HarryH's user avatar
  • 526
6 votes

Don't individual signal sources affect each other when using a summing amplifier?

The answer is in the schematic you provided. The inverting input is a "virtual earth". The amplifier is configured so that the output adjusts until the negative feedback causes the inverting input ...
Transistor's user avatar
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6 votes
Accepted

Finding load current in a circuit with voltage dependent voltage source

I cannot see how this can be solved without knowing RL (60.9 kohm) @Andyaka teacher is persistent about not giving RL, so I'm trying to find a way to get rid of RL Please note that my "answer&...
Andy aka's user avatar
  • 462k
6 votes

Why do I get two different answers for the current through the 47 kΩ resistor when I do a source transformation?

The only guarantee you get from from replacing any section of a circuit with some equivalent, is that conditions outside that replaced section will remain unchanged. There's nothing that says the ...
Simon Fitch's user avatar
  • 37.6k
5 votes
Accepted

why add a resistor parallel to voltage source?

You might change your mind if you unplugged the device and then touch the plug pins. The 1 MΩ resistor between live and neutral provides a discharge path for the capacitor. The discharge time ...
Transistor's user avatar
  • 177k
5 votes

How to run 5v relay on 9v?

You will put a resistor in series with the relay coil. The resistor value is selected in conjunction with knowing the DC resistance of the relay coil. The idea to select the resistor value so that the ...
Michael Karas's user avatar
5 votes

How to run 5v relay on 9v?

Place a ~4 V zener diode in series to drop the voltage. simulate this circuit – Schematic created using CircuitLab
winny's user avatar
  • 15.6k
5 votes

GND of 9V batteries in a circuit

You won't get "a lot of power" out of two 9V batteries because they don't have it. Outside of that, the circuit will work. The "REF GND" is particular to the simulator, and you don't need it in real ...
JRE's user avatar
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5 votes
Accepted

Ideal Voltage and Current Sources in series

The current source tells us that each element in this loop will have a current of 2mA flowing through it, including the resistor. Ohm's law tells us that $$V_{R} = I_{R}\cdot R_{R} = 2\ mA \cdot R_{R}...
Joren Vaes's user avatar
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5 votes

Simple way to boost from 24V to 24.8V? (up to 10A)

The range given by manufacturer (23.8 - 28 V) is the range of forward voltages that will appear on the string of LEDs if a constant 10 A current is applied. This voltage will depend on temperature and ...
Ale..chenski's user avatar
  • 40.9k
5 votes

Under which specific (formal) conditions can I apply the superposition theorem?

The superposition theorem works for any linear circuit. The problem with two voltage sources in parallel is that if their voltages are not identical then you have a nonsense circuit. Two different ...
Elliot Alderson's user avatar
5 votes

What is the physical meaning of negative resistance?

In this context, we have to discriminate between (1) pure differential (dynamic) neg. resistances (as shown in the examples of the other answers) and (b) a static negative resistance. For a ...
LvW's user avatar
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