Which is not a contributor to dynamic power?

Which is not a contributor to dynamic power?

• A. Switching activity.
• B. Capacitance.
• C. Leakage current.
• D. Voltage.

Answer: (C)

Dynamic power in digital circuits comes from charging and discharging capacitive loads as signals switch. Each transition injects energy into the load, roughly (1/2) C V^2, and the total dynamic power scales with how often switching occurs (switching activity), the amount of capacitance being charged (load capacitance), the supply voltage, and the clock frequency. So switching activity, capacitance, and voltage (and frequency) all drive dynamic power. Leakage current, however, is a static form of power. It flows even when no switching happens due to subthreshold and other leakage mechanisms in transistors, contributing to static power rather than dynamic power. That’s why leakage current does not contribute to dynamic power.

Dynamic power in digital circuits comes from charging and discharging capacitive loads as signals switch. Each transition injects energy into the load, roughly (1/2) C V^2, and the total dynamic power scales with how often switching occurs (switching activity), the amount of capacitance being charged (load capacitance), the supply voltage, and the clock frequency. So switching activity, capacitance, and voltage (and frequency) all drive dynamic power.

Leakage current, however, is a static form of power. It flows even when no switching happens due to subthreshold and other leakage mechanisms in transistors, contributing to static power rather than dynamic power. That’s why leakage current does not contribute to dynamic power.