Chapter 2 - Operational Amplifiers

Abstract

In all signal-processing systems, designers have to receive, amplify or attenuate, or process the analog signals using varieties of analog techniques. The operational amplifier (op amp) is one of most commonly used analog components for such tasks. This chapter provides a designer's viewpoint on the use of op amps, identifying their characteristics and limitations in a practical sense. There are four types of amplifiers: voltage amplifier, current amplifier, trans-impedance amplifier, and Trans-conductance amplifier. The ideal op amp must be always considered as a four-terminal device. The chapter discusses the input imperfections and the output obstacles of op amps. The actual characteristics of real op amps are considerably more complicated. There are three uncorrelated noise sources: two current sources (IN) and a voltage source (VN) that appear differentially. The output side of the model also is not ideal. There is an output impedance (Ro) in series with the voltage sources. In a modern approach, practical op amps available from the component manufacturers can be grouped into several categories, such as voltage feedback op amps; current feedback op amps; micro-power op amps; single supply op amps; chopper stabilized op amps; and wideband, high-speed, high-slew-rate op amps.