Operational amplifier applications

Operational amplifiers have several applications, optimised for use with negative feedback. When positive feedback is required, a comparator is usually more appropriate; see Comparator applications for further information. Practical considerations Fig. 1: an equivalent circuit of an operational amplifier that models some non-ideal parameters using resistances. A real operational amplifier has a finite input impedance R in {\displaystyle R_{\text{in}}} , a non-zero output impedance R out {\displaystyle R_{\text{out}}} , and a finite gain G {\displaystyle G} . In this article, a simplified schematic notation is used that ignores details such as device selection and power supply connections. Non-ideal properties (such as those shown in Fig. 1) are ignored. Operational amplifiers parameter requirements In order for a particular device to be used in an application, it must satisfy certain requirements. The operational amplifier must have large open-loop signal gain (voltage gain of 200,000 is obtained in early integrated circuit exemplars), and have input impedance large with respect to values present in the feedback network. With these requirements satisfied, one can use the method of