Which of the following options is INCORRECT for a feedback amplifier?

Feedback Amplifiers

Definition: A feedback amplifier is an electronic amplifier that uses feedback to control its gain, stability, and other characteristics. Negative feedback is commonly employed to improve performance by feeding a portion of the output signal back to the input in a manner that opposes the input signal.

Correct Option Analysis:

The correct option is:

Option 2: In a feedback topology, sampling the output current reduces the output impedance.

This statement is incorrect. Sampling the output current, in a feedback topology, does not inherently reduce the output impedance. Instead, when current sensing (sampling) is used in a feedback system, it affects the system's ability to control or modify the output based on the type of feedback network implemented. Output impedance reduction is typically associated with voltage sampling (not current sampling) in series-shunt feedback configurations. Therefore, the given statement does not accurately describe the behavior of feedback amplifiers.

Additional Information

To further understand the analysis, let’s evaluate the other options:

Option 1: In a feedback topology, sampling the output voltage reduces the output impedance.

This statement is correct. In a voltage-sampling (shunt) feedback configuration, the output impedance of the amplifier is reduced. This reduction occurs because the feedback network effectively modifies the output characteristics of the system, making it more stable and less sensitive to changes in load conditions.

Option 3: The gain-bandwidth product remains constant for a negative feedback amplifier.

This statement is also correct. Negative feedback amplifiers are designed to maintain a constant gain-bandwidth product. When the gain is reduced due to feedback, the bandwidth increases proportionally to maintain the product constant. This is a fundamental characteristic of feedback amplifiers and is one of the reasons why negative feedback is widely employed in amplifier design.

Option 4: Negative feedback minimizes nonlinear distortion in the amplifier's output.

This statement is correct. Negative feedback reduces nonlinear distortion by linearizing the amplifier's operation. By feeding back a portion of the output to the input, the system compensates for deviations from linearity, thereby improving the fidelity of the output signal.