Perhaps the most versatile and important analog integrated circuit for the student to master is the operational amplifier, or op-amp. Essentially nothing more than a differential amplifier wit-h very high voltage gain, op-amps are the workhorse of the analog design world. By cleverly appl-ying feedback from the output of an op-amp to one or more of its inputs, a wide variety of beha-viors may be obtained from this single device. Many different models of op-amp are available at a low cost.