Q1: The power dissipation, P_D, of a logic gate is the product of the ________.

ANS:B - dc supply voltage and the average supply current

Power Dissipation is an important metric for two reasons. Amount of current and power available in a battery is nearly constant. Power dissipation of a circuit or system defines battery life, The greater the power dissipation, the shorter the battery life. Power dissipation is proportional to the heat generated by the chip or system, Excessive heat dissipation may increase operating temperature and cause gate circuitry to drift out of its normal operating range, will cause gates to generate improper output values. Thus power dissipation of any gate implementation must be kept as low as possible.

Other this, power dissipation can be classified into static power dissipation and Dynamic power dissipation.

Ps (Static Power Dissipation) : Power consumed when the output or input are not changing or rather when clock is turned off. Normally static power dissipation is caused by leakage current. (As we reduce the transistor size, i.e. below 90nm, leakage current could be as high as 40% of total power dissipation).

Pd (Dynamic Power Dissipation) : Power consumed during output and input transitions, So we can say Pd is actual power i.e. power consumed by transistors + leakage current.

Thus total power dissipation is

Total power dissipation = static power dissipation + dynamic power dissipation.