Page 53 - Op Amps Design, Applications, and Troubleshooting

CHAPTER TWO

Amplifiers

2.1 AMPLIFIER FUNDAMENTALS

2.1.1 Gain
This chapter focuses on the analysis and design of several basic amplifier cir-
cuits. Not only is the amplifier circuit a fundamental building block in linear
circuits, but the analytical techniques introduced in this chapter will greatly
enhance your ability to analyze the circuits presented in subsequent chapters.
Regardless of the specific circuit application (e.g., summing circuit, active filter,
voltage regulator, and so forth), the op amp itself is simply an amplifier. There-
fore, a thorough understanding of op amp behavior in circuits designed specifi-
cally as amplifiers will provide us analytical insight that is applicable to nearly
all op amp circuits.
An amplifier generally accepts a small signal at its input and produces a
larger, amplified version of the signal at its output. The gain (A) or amplification is
expressed mathematically as

We may speak of voltage gain, current gain, or power gain. In each of these cases
the above equation is valid. If, for example, a particular voltage amplifier pro-
duced a 5-volt RMS output when provided with a 2-volt RMS input, we would
compute the voltage gain as

36