Static power retention.

Static power retention.

• A. It disappears at power-down.
• B. It depends primarily on switching activity.
• C. It remains constant regardless of leakage.
• D. It persists as leakage when idle.

Answer: (D)

Static power retention is about the power that remains dissipated when a circuit is idle due to leakage currents. In modern devices, transistors aren’t perfect switches; there is subthreshold leakage where current flows from supply to ground even when a transistor is “off,” along with gate-oxide and junction leakage. When the circuit is not switching but still powered, these leakage paths continuously draw current, so power is wasted during idle periods. This baseline leakage current makes static power persist, unlike dynamic power which only appears when the circuit is actively switching and charging/discharging capacitances. If the supply is truly removed, power dissipation stops, but as long as the circuit has power, the leakage sets the static power level.

Static power retention is about the power that remains dissipated when a circuit is idle due to leakage currents. In modern devices, transistors aren’t perfect switches; there is subthreshold leakage where current flows from supply to ground even when a transistor is “off,” along with gate-oxide and junction leakage. When the circuit is not switching but still powered, these leakage paths continuously draw current, so power is wasted during idle periods. This baseline leakage current makes static power persist, unlike dynamic power which only appears when the circuit is actively switching and charging/discharging capacitances. If the supply is truly removed, power dissipation stops, but as long as the circuit has power, the leakage sets the static power level.