Suppose a unit inverter with three units of input capacitance has unit drive.

a) What is the drive of a 4x inverter?

b) What is the drive of a 2-input NAND gate with three units of input capacitance?

Refer to equation 4.24 in the textbook to recall that if a unit inverter is defined to have one unit of input capacitance then the drive of the gate is,

x = Cin/g

Here, Cin is the input capacitance, and g is the logical effort of the gate.

Consider a unit inverter with 3 units of Cin and a single unit of x.

Recall that an inverter has a logical effort of 1.

Therefore, modify the equation for this inverter.

x = Cin/3g

Here, Cin is divided by 3 to match the unit drive value.
(a)
Consider a 4x inverter.