Digital Systems

Chapter 6

Logic Gates

OBJECTIVE

In this chapter, we shall study RTL, DTL, TTL, ECL, ICL, HTL, NMOS and CMOS logic gates; the difference between the various families of gates and their speeds; propa- gation delay; operating frequency; power dissipated per gate; supply-voltage levels; and operational-voltage levels that define logic states 1 and 0.

In Chapter 4, we learnt six digital electronics logic operations used as basic operations in the complex circuits. These are NOT, NAND, AND, OR, NOR and XOR. We also learnt that an interesting combination is NOT-XOR (recall the Figures 4.1 and 4.2). There are the different types of circuits of the logic gates for implementing these operations; RTL, DTL, TTL, ECL, ICL, HTL, NMOS and CMOS. How are ...