Deep Dive: E7D02
The correct answer is B: By varying the duty cycle of pulses input to a filter. How does a switchmode voltage regulator work is by varying the duty cycle of pulses input to a filter. Switchmode regulators vary duty cycle to control output. For amateur radio operators, this is important for power supply design. Understanding this helps when working with switching regulators.
Why Other Answers Are Wrong
Option A: Incorrect. Alternating output between positive and negative voltages isn't switchmode - switchmode varies duty cycle. Alternating output isn't switchmode. Option C: Incorrect. Varying conductivity of pass element isn't switchmode - that's linear regulator. Varying conductivity isn't switchmode. Option D: Incorrect. Switching between two Zener reference voltages isn't switchmode - switchmode varies duty cycle. Zener switching isn't switchmode.
Exam Tip
Switchmode voltage regulator works = by varying duty cycle of pulses input to filter. Think 'S'witchmode = 'S'witching 'D'uty cycle. Switchmode regulators vary duty cycle to control output. Not alternating output, not varying conductivity (linear), not Zener switching - just varies duty cycle.
Memory Aid
Switchmode voltage regulator works = by varying duty cycle of pulses input to filter. Think 'S'witchmode = 'D'uty cycle. Switchmode regulators vary duty cycle to control output. Important for power supply design.
Real-World Example
A switchmode voltage regulator: It works by varying the duty cycle of pulses input to a filter. The switch turns on and off rapidly, and the duty cycle controls the average output voltage. This is how it works - varies duty cycle.
Source & Coverage
Question Pool: 2024-2028 Question Pool
Subelement: E7D
Reference: 2024-2028 Question Pool · E7 - Practical Circuits
Key Concepts
Verified Content
Question from the official FCC Extra Class pool. Explanation reviewed by licensed amateur radio operators and mapped to the E7D topic.