# Bandwidth of Circuit

Question: What is the bandwidth of the circuit OR What do you mean by bandwidth of circuit?

Answer: Bandwidth or BW of the resonant circuit is defined as the difference between the frequencies at which the circuit delivers half of the maximum power.

Consider the figure below:

The graph is the power response of a series resonant circuit. Here the bell-shaped curve is known as the selectivity curve. One can see that frequency values around ωs have all significant amounts of power to be dissipated.

BW on the x-axis implies the bandwidth of the resonant circuit, which is actually the difference between the frequencies for which the circuit will deliver half of the maximum power.

The other two frequencies on the right and left side of ωs are ω1 and ω2. These are called the half-power frequencies, or band frequencies, or cutoff frequencies.

Related to BW is another concept namely the Q factor or quality factor that is actually a measure of the “goodness” or quality of a resonant circuit. You can read more about QF here.

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