Bandwidth is defined at magnitude drop to:

• A. 70.7%
• B. 90%
• C. 50%
• D. 10%

Answer: (A)

Bandwidth is a crucial concept in electronics and signal processing, often defined in terms of the frequency range over which a system operates effectively. The definition involves the magnitude of a signal and how it changes with frequency.

When discussing bandwidth in the context of filters and circuits, it is typically defined at the point where the output power drops to half of its maximum value. In terms of voltage, this corresponds to a magnitude drop to approximately 70.7% of the peak amplitude. This percentage is derived from the relationship between power and voltage, where power is proportional to the square of the voltage (P ∝ V²). A drop to half power means that the voltage drops to ( V_{max} / \sqrt{2} ), which is roughly 0.707 or 70.7%.

Recognizing this standard is essential for understanding how filters and amplifiers behave across different frequencies, making the identification of bandwidth critical in designing and analyzing electronic systems. Other percentages like 90%, 50%, or 10% do not conform to the standard definition of bandwidth in this context.