Page 391 - Basic Electrical Engineering
P. 391
f and f are the higher and lower bandwidth frequencies. Let us now
2
1
calculate the value of f / (f – f )
1
2
0
Quality factor Q as we have seen earlier is
Thus,
From eq. (3.20), it is seen that if the quality factor is high, bandwidth will be
narrow. The circuit will, therefore, allow only a narrow band of signal
frequencies which are close to the resonant frequency. Such a circuit is,
therefore, highly selective in allowing signals to pass through. High-quality-
factor resonant circuits are also called ‘tuned circuits’, which will be studied
in detail in electronic circuit design.
We have seen earlier that power dissipated at cutoff frequencies is half the
power dissipated at resonant frequency. Hence, the cutoff frequencies f and
1
f are also called half-power frequencies.
2
Example 3.33 An R–L–C series circuit has R = 10 Ω, L = 0.1 H, and C = 8
μf.
Calculate the following:
