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What's the physical significance of Q factor?

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deepa

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well there are so many definitions the Quality factor,,but can any one please clearly explain what is the physical significance of this quantity,,
there is Q of a filter ,Q of a damping system,Q of a coil or a capacitor..
Does the Q in all these cases mean the same?
 

Re: Q factor

hi,
yes there are simillar. but parametrers are not the same
Q (Low pass and High pass) filter=L/R=r/c=BW3dB/f0
but Q Band pass filter and band reject filter=BW3dB/f0
Q self= L/r
 

Re: Q factor

i need to know the physical meaning of the quality factor in circuits
 

Q factor

Read Tom Lee's RF CMOS IC Design book
 

Re: Q factor

Basically Q-factor is the reciprocal of various loss tangents viz. loss tangents due to dc resistance, loss tangents due to ac resistance (skin effect and proximity effect), loss tangents due to dielectrics. Higher the Q-factor, lower will be the heat dissipation in the circuit.
In other words, Q-factor is the ratio of reactive power stored to the active power dissipated. Its the quality of the circuit that how much power it can stored.
Based on Q-factor , efficiency of LC-tank circuit can be defined as
Efficiency = (Qunloaded - Qloaded)/Qunloaded
Higher the Q, better will be selectivity of the LC-tank circuit.
 

Re: Q factor

In my opinion, the physical meaning of the Q factor is that the times or numbers of oscillation for the defined energy.
 

Re: Q factor

The tank circuit for which the Q is defined exchange the electromagnetic field energy every half cycle from magnetostatic energy to electrostatic energy. The 2*pi/Q factor is physical the relative loss of energy over one cycle.

You derive this by the equation deltaE/E where

deltaE=(ipeak^2*R/2)/Ftank and

E=(ipeak^2*L/2)

you end up in deltaE/E=2*pi/Q where Q=2*pi*Ftank*L*R
 

Re: Q factor

i don understand clearly wat is Ftank.and the Q i know of a tank ciruit is 1/R .(L/C)Λ 0.5..
 

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