MOS logic gates are by far the most popular choice for realizing digital integrated circuits at the present time. This is primarily due to the large number of MOS transistors that can be fabricated in a single integrated circuit. MOS logic gates were introduced in Chapter 1, where the transistors were modeled very simply as switches. In this chapter, we shall analyze the MOS gate circuits in greater detail, now that a more complete understanding of MOS transistors and the MOS IC fabrication process has been gained.

Although, the logic family called CMOS logic is by far the most popular due to its low power dissipation, a different logic family called pseudo-NMOS technology will be discussed first. This logic family is realized primarily using n-channel transistors with a single p-channel transistor used as the load for each logic gate. The design of these logic gates is very similar to what was used previously for the NMOS logic family, which was the first technology that allowed for the manufacture of very large-scale integrated (VLSI) circuits. Pseudo-NMOS gates are not used very often in actual ICs (except perhaps for programmable logic arrays, which are described in Chapter 10) because they dissipate power even when their outputs are not changing. However, they are simple, result in dense circuitry, are moderately fast when capacitive loading is small, and are designed in a manner similar to many other logic families. An example of this is a logic family that is realized using the very high-speed...