Questions tagged [current-source]

An electronic component that sources current - if it sinks current it is called a current sink but both devices (sinks and sources) can be called sources. An IDEAL current source will supply current, maintain high voltage compliance (i.e. adapt its output voltage to match the network it is supplying current to) and have an infinite output impedance. In non-ideal implementations current sources have limited operating ranges and finite output impedances.

An electronic component that sources current - if it sinks current it is called a current sink but both devices (sinks and sources) can be called sources. An ideal current source will supply current, maintain high voltage compliance (i.e. adapt its output voltage to match the network it is supplying current to) and have an infinite output impedance. In non-ideal implementations current sources have limited operating ranges and finite output impedances.

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How to get more than 100mA from a USB port

I heard that the current limit for a USB port is 100mA. However, I also heard that some devices can get up to 1.8A from a port. How do you get past the 100mA limit?
200ok404notfound
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What exactly is a current source?

What I understood from the definition of current sources is that it is a source which supplies a constant current across a load no matter how the other parameters (like resistances for example) in the circuit are changed. Am I right? If I'm right,…
Green Noob
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Choosing resistor values for inverting amplifier and why?

The gain here is A = -R f /Rin. However, lets say I want a gain of 10 V/V. Which resistor value would you choose and why? I know that you could have infinite number of combinations for these resistors but why would some one use specific value. i.e R…
dr3patel
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What does a two overlapping circles symbol mean in an electrical schematic/diagram?

In the datasheet for a A3503 Hall Effect Sensor, I saw a circuit diagram labeled 'Functional Block Diagram', and it shows a symbol I have not seen before. It's shown here between 3 - Output and 2 - Ground. What is this supposed to represent? The…
Ehryk
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What's the intuition for reading transistor/resistor circuits?

The below circuit supposedly provides constant current to an LED. I tested using everycircuit.com and that seems correct (used R = 70 ohm for example). What's a step by step way of thinking about the flow of electrons in such a circuit? How can we…
JC123
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Increasing the compliance voltage range for a variable, two-quadrant constant current pin-driver circuit

The following is for hobbyist work and I have no commercial intentions at all. Only a handful (two?) will be built. (I use these for part testing and curve generation, though with the higher voltage compliances I may find still more uses than…
jonk
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How do we create current sources?

Constant current sources (simply, current sources ) are useful and necessary devices. They are widely used to drive LEDs, charge capacitors and batteries, to bias differential amplifiers, etc. The only problem is... there are no such devices in…
Circuit fantasist
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Do constant current batteries exist?

Do constant current batteries exist? If not, why not? Else, why are they not very common in the market? I am not talking about an ideal current source. But it should be a constant current source for few range of values (load, voltage or something).…
nidhin
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What are some practical examples of a constant current source?

Please don't state the obvious that nothing is a perfect constant current source. And please do not give examples of how to create them from components. I looked at this SE Q/A which stated the obvious - that you can not have a perfect current…
jennifer
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How does adding a current source and extra resistor to source follower improve its performance?

This question is similar to FET - Source follower utilizing current source to lower voltage offset , although I do not entirely understand the explanations, which is why I am posting my own question. As part of an electronics lab, I was asked to…
corgiworld
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op amp+mosfet = current source.Why do we need a feedback resistor?

The feedback resistor is needed to compensate for the error of the input currents? How to choose the resistance R2. Circuit source Resistor R2. Can I use this circuit, op-amp with differential input voltage range = +/- 0.6V? I'm not sure. I think not
AndreyB
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What does a voltage or current source actually output?

Current is the rate at which electrons flow through a circuit, and voltage is the potential "drop" between two points in a circuit. Do voltage sources output an unknown current, and vice versa? Why aren't they the same, if V=IR when there is no…
Asia B
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Why would you attach a Diode to the base of a BJT?

I was looking at a DC BJT setup for sourcing current and came accross this I have never seen a diode attached to the base of BJTs before and was wondering what it might be used for? I believe it might be used for compensation due to effects in…
user1207381
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Where does this current source symbol come from?

There's an old symbol for a current source that's just two overlapping circles, reminiscent of a Venn diagram. There is more than one question on here with people asking what the symbol is, but I'm interested to know where it comes from; is it just…
Hearth
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What's the point of a current source?

simulate this circuit – Schematic created using CircuitLab OK. So I've been told that the current flowing into the current source (that is, into the arrow's behind) is the same as the current coming out of the current source (that is, out of the…
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