TABLE OF CONTENTS This chapter of the book discusses several popular types of specialty amplifiers, or amplifiers that are based in some way on op amp techniques. However, in an overall applications sense, they are not generally used as universally as op amps. Examples of specialty amplifiers include instrumentation amplifiers of various configurations, programmable gain amplifiers (PGAs), isolation amplifiers, and difference amplifiers.
Other types of amplifiers, for example such types as audio and video amplifiers, cable drivers, high-speed variable gain amplifiers (VGAs), and various communications-related amplifiers might also be viewed as specialty amplifiers. However, these applications are more suitably covered in Chapter 6, within the various signal amplification sections.
Walt Kester, Walt Jung
Probably the most popular among all of the specialty amplifiers is the instrumentation amplifier (hereafter called simply an in amp). The in amp is widely used in many industrial and measurement applications where dc precision and gain accuracy must be maintained within a noisy environment, and where large common-mode signals (usually at the ac power line frequency) are present.
An in amp is unlike an op amp in a number of very important ways. As already discussed, an op amp is a general-purpose gain block user-configurable in myriad ways using external feedback components of R, C, and, (sometimes) L. The final configuration and circuit function using an op amp is truly whatever the user makes of it.
In contrast to this, an in...
