What describes static power in digital circuits?

What describes static power in digital circuits?

• A. Static power is consumed when idle due to leakage.
• B. Dynamic power is consumed during switching as capacitances charge/discharge.
• C. Static power increases with switching frequency.
• D. Power is only consumed when the circuit is powered on.

Answer: (A)

Static power is the constant power draw from leakage currents in transistors even when no logic is switching. In modern CMOS, leakage comes from subthreshold conduction, gate-oxide leakage, and junction leakage, so as long as the supply is on there’s a small but real current flowing. That’s why describing static power as the power consumed when idle due to leakage is the best answer. Dynamic power, in contrast, comes from charging and discharging capacitive loads during transitions and scales with switching activity (frequency and toggling), which is why the other statements don’t describe static power. The idea that static power increases with switching frequency is incorrect because frequency mainly drives dynamic power, not leakage. And saying power is only consumed when the circuit is powered on ignores the fact that leakage draws current even in idle, as long as the supply is present.

Static power is the constant power draw from leakage currents in transistors even when no logic is switching. In modern CMOS, leakage comes from subthreshold conduction, gate-oxide leakage, and junction leakage, so as long as the supply is on there’s a small but real current flowing. That’s why describing static power as the power consumed when idle due to leakage is the best answer. Dynamic power, in contrast, comes from charging and discharging capacitive loads during transitions and scales with switching activity (frequency and toggling), which is why the other statements don’t describe static power. The idea that static power increases with switching frequency is incorrect because frequency mainly drives dynamic power, not leakage. And saying power is only consumed when the circuit is powered on ignores the fact that leakage draws current even in idle, as long as the supply is present.