OVERVIEW

This chapter uses the basic subcircuits of the last chapter to develop various forms of CMOS amplifiers. We begin by examining the inverter the most basic of all amplifiers. The order of presentation that follows has been arranged around the stages that might be put together to form a high-gain amplifier. The first circuit will be the differential amplifier. This serves as an excellent input stage. The next circuit will be the cascode amplifier, which is similar to the inverter, but has higher overall performance and more control over the small-signal performance. It makes an excellent gain stage and provides a means of compensation. The output stage comes next. The objective of the output stage is to drive an external load without deteriorating the performance of the high-gain amplifier. The final section of the chapter will examine how these circuits can be combined to achieve a given high-gain amplifier requirement.

The approach used will be the same as that of Chapter 4, namely, to present a general understanding of the circuit and how it works, followed by a large-signal analysis and a small-signal analysis. In this chapter we begin the transition in Fig. 4.0-1 from the lower to the upper level of simple circuits. At the end of this chapter, we will be in a position to consider complex analog CMOS circuits. The section on architectures for high-gain amplifiers will lead directly to the comparator and op amp.

As the circuits we study become more complex, we will have an...