A Low Pass RC filter behaves as a High Pass RC filter if the voltage source is replaced by a current source. What is an intuitive explanation to this phenomenon?
thanks I get it now.
gauthamtechie,
- - - After all, a current source is a voltage in series with a large resistance. That is bound to change the characteristics of the circuit. Although others have said otherwise. - - -
Ratch
Hmmm, would you please elaborate?
A current source may be equivalent to a voltage source and a resistance in series, but one can construct a true current source w/o a large series resistance. Take an inductor based LED constant current driver. When the inductor is energized with the FET turned on, the energy in the inductor is stored as L*I^2/2. Then the FET opens, and the inductor current free wheels through the catch diode and LED.
For high efficiency this approach is used. The inductor outputs a constant current. The voltage is determined by the LED and catch diode. There is no large series resistance. If there were the losses would be great, an undesirable thing.
Ratch you post some stuff that I just cannot believe that you even believe. How can you think that an inductor supplying a current really consists of a voltage source plus large series resistance? Measurements confirm the opposite.
"...but one can construct a true current source..."
Just one comment from my side: I think, this statement must be elaborated as well.
1.) What is a "true current source"?
2.) Is there any voltage source "behind"?
Remember: What is this thing called "current"? It is movement of charges, is it not?
And which force is it that causes the charges to move? Isn`t it a voltage (resp. the corresponding field) ?
W.
Hi Claude,
thank you for the detailed answer. Of course - I must agree, no doubt about the definitions you have mentioned.
My only concern was the formulation "...one can construct a true current source" (construct !).
W.
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