TABLE OF CONTENTS Operational amplifiers (op amps) can be used to create (1) precision current sources and sinks, which range from submicroamps to milliamps, and (2) current regulators, which range from milliamps to amps. Equipment and instrumentation designers have used the op amp for these purposes for many years past, in fact ever since the third or fourth generation of op amps was introduced. Those products brought with them greater stability and were much more affordable than their predecessors. In this chapter we will look at how to use the op amp in both current source and current regulator applications, but first we will take a brief look at how today's op amp evolved.
An op amp circuit was first created during World War II for the U.S. military by an American scientist Loebe Julie. Following World War II, a few small companies emerged and started looking at analog computer applications. The best-known pioneer was Philbrick Researches, whose founder, another American engineer, George A. Philbrick, was the pioneer of both the op amp and of analog computing. In the late 1940s and early '50s, this original op amp circuit was constructed using several vacuum tubes, to form a multistage amplifier block. Julie's best design, known as the K2W, was adopted by Philbrick, which successfully commercialized it. Eager buyers include instrumentation and analog computer makers.
Initially, Philbrick made op amp circuits with vacuum tubes, but once the transistor became available, the company switched to making circuits with germanium transistors.
