Question
Which of the following can be used to determine the Q of a series-tuned circuit?
Answer Options
- A) The ratio of inductive reactance to capacitive reactance
- B) The frequency shift
- C) The bandwidth of the circuit’s frequency response
- D) The resonant frequency of the circuit
Correct Answer: C
Explanation
The Quality factor, or Q, of a resonant circuit (like an RLC circuit used for filtering or impedance matching) is a measure of the circuit’s selectivity. A higher Q indicates a sharper response, meaning the circuit responds strongly only to a very narrow range of frequencies. This characteristic is defined by the circuit’s internal resistance relative to its reactance.
Practically, the easiest way to measure the Q of a tuned circuit is to measure its frequency response. The Q is calculated directly using the relationship Q = F_R / \Delta F, where F_R is the resonant frequency and \Delta F is the bandwidth of the circuit’s frequency response (specifically, the half-power bandwidth). Measuring the -3 \text{ dB} bandwidth is therefore essential for determining the circuit’s Q.
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