Question

In CMOS logic design, if the supply voltage is halved, by what factor is the dynamic power dissipation reduced, assuming frequency and load capacitance remain constant?

Accepted Answer

The dynamic power dissipation in a CMOS circuit is calculated using the formula P = C * V^2 * f, where P is power, C is the load capacitance, V is the supply voltage, and f is the switching frequency. Load capacitance refers to the amount of electrical charge stored by the circuit gates, while switching frequency is the rate at which those gates transition between states. Because the supply voltage V is squared in this relationship, any change to the voltage has a quadratic effect on the power consumption. If the supply voltage is halved, the new voltage becomes 0.5V. When this value is squared in the formula, (0.5)^2 equals 0.25. Therefore, halving the supply voltage reduces the dynamic power dissipation by a factor of four, or to 25 percent of its original value.

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In CMOS logic design, if the supply voltage is halved, by what factor is the dynamic power dissipation reduced, assuming frequency and load capacitance remain constant?

The dynamic power dissipation in a CMOS circuit is calculated using the formula P = C * V^2 * f, where P is power, C is the load capacitance, V is the supply voltage, and f is the switching frequency. Load capacitance refers to the ....