CMOS Analog and Mixed-Signal Circuit Design

3	Amplifiers

3.1      INTRODUCTION

This chapter provides a brief introduction to the basic complementary metal-oxide semiconductor (CMOS) amplifier, in particular, the two-stage CMOS amplifier. This chapter use the signal path as design insight. A new technique called the current density approach is also discussed in the last part of this chapter.

3.1.1      CMOS AMPLIFIER

Figure 3.1 shows a two-stage operational amplifier. Reference current Iref is generated/sourced from a voltage reference circuit. The input stage together with M₁₂ and M₁₄ forms a folded cascade configuration. M₁₅ and M₁₆ act as an active load for the first-stage amplifier. The output stage is a common source amplifier with a compensation capacitor. M₁₈ acts as a load. ...