Op amps are presently in wide use in just about every aspect of linear electronics. An op amp is a multi-stage amplifier treated as a single entity. The first stage usually utilizes a differential amplifier that can be made with either bipolar or FET devices. The following stage(s) create a large voltage gain. The final stage is a class B voltage follower. The resulting op amp typically has a high input impedance, a low output impedance, and voltage gains in excess of 10,000. The op amp operates from a bipolar power supply, usually around $$\pm$$15 V. Externally, it has connections for the inverting and noninverting inputs, the single-ended output, and the power supplies. The op amp may be packaged in a variety of forms, including DIPs, SIPs, cans, flat packs and surface mount.