Operational amplifiers are undoubtedly the easiest and best way of performing a wide range of linear functions from simple amplification to complex analog computation. The cost of monolithic amplifiers is now less than $2.00， in large quantities， which makes it attractive to design them into circuits where they would not otherwise be considered. Yet low cost is not the only attraction of monolithic amplifiers. Since all components are simultaneously fabricated on one chip， much higher circuit complexities than can be used with discrete amplifiers are economical. This can be used to give improved performance. Further， there are no insurmountable technical difficulties to temperature stabilizing the amplifier chip， giving chopper-stabilized performance with little added cost. Operational amplifiers are designed for high gain， low offset voltage and low input current. As a result， dc biasing is considerably simplified in most applications; and they can be used with fairly simple design rules because many potential error terms can be neglected. This article will give examples demonstrating the range of usefulness of operational amplifiers in linear circuit design. The examples are certainly not all-inclusive， and it is hoped that they will stimulate even more ideas from others. A few practical hints on preventing oscillations in operational amplifiers will also be given since this is probably the largest single problem that many engineers have with these devices.