What information does a Bode plot convey about a linear time-invariant system?

• A. Time-domain impulse response
• B. Nyquist plot of poles and zeros
• C. A plot of magnitude (and phase) of the frequency response vs log frequency
• D. Voltage-current characteristic at a fixed frequency

Answer: (C)

A Bode plot communicates how an LTI system responds to sinusoidal inputs across a range of frequencies, showing both gain and phase as frequency changes. It is typically two graphs: magnitude of the frequency response (often in decibels) plotted versus frequency on a logarithmic scale, and the phase of the frequency response plotted versus frequency on the same log scale. This lets you see how the system amplifies or attenuates each frequency component and how much phase shift is introduced, which reveals filter type (low-pass, high-pass, band-pass), bandwidth, and any resonant behavior. It’s also useful for assessing stability margins in feedback, by indicating how the gain and phase evolve with frequency.

This view is different from time-domain impulse response, which is the system’s reaction to a delta input. It doesn’t directly show a Nyquist plot, and it doesn’t depict a voltage-current characteristic at a fixed frequency.