Lumped Circuit Element

[devonsc]

Hi there, just a short post here. If it is not too much trouble, can anyone explain briefly or define what does it mean by lumped circuit element?

I come across this term in some communication books, which involves the transmission lines. Am I right to say that it is actually a low frequency network?

 

[seansscheng]

"lumped" means that the dimension of you ckt element is much smaller than the wavelength of the signal passing through it. Therefore, you can treat your ckt element as a lumped unit (against the wavelength), and do not have to worry about wave propagation phenomenon "within" your ckt element. The opposite of "lumped element" is "distributed network."

Typically, in low-frequency ckt/network, since the frequency is low, therefore, the wavelength is large (wavelength = propagation speed(usu. speed of light) / frequency ), so most elements can be treated as lumped. However, as frequency goes higher and higher, the wavelength becomes shorted and shorter, the wave propagation effect WITHIN the ckt element becomes more and more pronounced.

I hope the above explanation help. Thanks.

 

[DrDolittle]

Let me tell you that in terms of Transmission level.
Along a transmission line there are inductive and capacitive reactances given raised by Ferranti Effect etc.Hence such parameters can be assumed to get scatterd along the distribution or either lumped.When they are lumped it is easier to calculate such impedance effects.Yes,you are right they are used for low frequency signals.When high frequency signlas are used a more rigorous mathematical treatment is employed.

Regards
drdolittle

 

[chingtang]

You may want to read "Lumped Elements for RF and Microwave Circuits" by Inder Bahl for more detail.

 

[masai_mara]

As mentioned above the lumped parameters agrument assumes that the cicuit parameters like R,L & C can be taken as fixed quantities for a circuit, this makes the calculations easier with circuit equations for voltage and current and is fairly accurate for low frequency applications. But for higher frequnecies with the above assumption you end up with inaccurate results hence you go for more rigorius approach with distributed parameters which take into account the dimensions of the circuit and uses transmission line equations.

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