Part 1: Topic 5 - Power Analysis

Question 1

CMOS Switching Energy During Rise Time: What is the equation for the energy delivered by the supply?

Answer 1

Question 2

CMOS Switching Energy During Rise Time: What is the equation for the energy dissipated in a MOSFET?

Answer 2

Question 3

CMOS Switching Energy During Rise Time: What is the equation for the energy stored in the load capacitor?

Answer 3

Question 4

CMOS Switching Energy: Why is the energy dissipated 0.5C_loadV_DD² everytime the inverter switches?

Answer 4

When the input of the inverter is switched again, the charge stored in the capacitor flows through the on n-MOSFET to ground. The energy stored in the capacitor is dissipated in the n-MOSFET. No energy is drawn from the power supply as the pMOSFET is off. Thus the energy dissipated each time the inverter switches is 0.5C_loadV_DD².

Question 5

CMOS: What effect does reducing the threshold voltage have?

Answer 5

decreasing V_t reduces delay but also increases leakage power consumption.