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# Dependent Current Source

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#### cwible

##### New Member
Hi guys,

I'm in an introductory EE class and I was wondering, if the dependent variable of a dependent current source is zero, does the dependent current source become a short circuit or open circuit?

Thanks for the help.

An ideal current-source has an infinite impedance so I would expect it to look like an open circuit.

You could call it a NoOP (Software instruction that does nothing, except waste some time)

https://www.ti.com/lit/an/snoa474a/snoa474a.pdf

short answer: a current source is a high impedance (infinite for an ideal CS), but in the real world can be anywhere from a high impedance, to a high negative impedance due to resistor mismatches (specifically in a Howland CS... BJT and FET CS circuits don't have similar feedback paths)

Hi guys,

I'm in an introductory EE class and I was wondering, if the dependent variable of a dependent current source is zero, does the dependent current source become a short circuit or open circuit?

Thanks for the help.

Any ideal current source has an infinite internal impedance and a infinite amount of voltage available to enforce its designated current value. Whether the ideal dependent source is commanded to supply a particular amount of current or no current at all does not change its internal impedance. So, if no current is coming from a dependent source, does the circuit "see" any difference of impedance than if a independent current source is outputting no current?

Think of it this way. A dependent current source would have to have an infinite impedance in order to keep its current at the zero value. What does an infinite impedance suggest in terms of whether it is a open or short circuit?

Ratch

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