Question

The bandwidth of an RF tuned amplifier is dependent on Q-factor of

• A. \( \text{Tuned output circuit} \)
• B. \( \text{Tuned input circuit} \)
• C. \( \text{Operating point} \)
• D. \( \text{Output, input circuits and quiescent point} \)

Hint:

In RF tuned amplifiers, always associate bandwidth with the **Q-factor of the tuned circuit**, especially the **output circuit**, as it governs the frequency selectivity. Use the relation: \[ \text{Bandwidth} = \frac{f_0}{Q} \] to estimate or understand behavior in such circuits.

Answer 1

The Correct Option is A

To solve this problem, we need to understand how the bandwidth of a radio-frequency (RF) tuned amplifier is affected by the Q-factor of various components.

1. Understanding Q-factor and Bandwidth:

- Q-factor (Quality Factor): The Q-factor is a measure of the selectivity or sharpness of the resonance in a tuned circuit. It is defined as the ratio of the resonant frequency to the bandwidth of the circuit:

\[ Q = \frac{f_0}{\Delta f} \]

where \( f_0 \) is the resonant frequency and \( \Delta f \) is the bandwidth. A higher Q-factor indicates a narrower bandwidth, and a lower Q-factor indicates a wider bandwidth.

2. Bandwidth of RF Tuned Amplifier:

The bandwidth of an RF tuned amplifier is primarily influenced by the Q-factor of the tuned circuits in the amplifier. These circuits are responsible for selecting the desired frequency, and their Q-factor determines how sharply the circuit resonates around that frequency.

- Tuned Output Circuit: The Q-factor of the tuned output circuit plays a significant role in determining the bandwidth of the amplifier. A high Q-factor results in a narrow bandwidth, while a low Q-factor leads to a wider bandwidth.

- Tuned Input Circuit: Similarly, the Q-factor of the tuned input circuit also affects the amplifier’s bandwidth, although its influence may not be as pronounced as that of the output circuit.

- Operating Point: The operating point (or quiescent point) determines the amplifier's linearity but does not directly affect the bandwidth as much as the Q-factors of the input and output circuits do.

3. Final Answer:

The bandwidth of an RF tuned amplifier is most strongly dependent on the Q-factor of the Tuned output circuit, though the tuned input circuit and operating point can also influence the overall performance.