Which CMOS gate network in Fig can operate at the highest fr

Which CMOS gate network in Fig. can operate at the highest frequency? Explain your answer.

Solution

There are losses and delays associated with CMOS swtching. Each NOT is implemented by a fixed number of CMOS elements and each input of AND is handled by fixed number of CMOS.

Each NOT gate if apprearing before AND or OR has 2 CMOS associated with it like in (a) and if after AND or OR gate, each input can be implemented by 2 CMOS.

Each input to or and and is implemented by 3 CMOS.

so a) needs 34 CMOS.

b) needs 24

c) needs 26.

Since C has lowest number of CMOS, it can operate at highest frequency.