Chapter 13 - Understanding Op Amp Parameters

Abstract

This chapter discusses the op amp data sheet parameters. There are usually three main sections of electrical tables in op amp data sheets. As the name of the table implies, some of it is composed of parameters and some test conditions. Test conditions are conditions placed on the op amp when the parameters are measured. Some abbreviations are used for both a condition and a parameter. Further, the open loop voltage gain parameter, AOL, is defined as the ratio of change in output voltage to the change in voltage across the input terminals. Usually, the DC value and a graph showing the frequency dependence are shown in the data sheet. It is expressed either unitless or in decibels. AOL is similar to the open loop gain, AVD, of the amplifier except that AVD is usually measured with an output load. AOL is usually measured with no load. Both parameters are measured as an open loop. The differential large signal voltage amplification parameter is the ratio of change in output voltage to the change in voltage across the input terminals. It is expressed either unitless or in decibels. AVD is sometimes referred to as differential voltage gain. AVD is a design issue when precise gain is required. This is because the higher the open loop gain for the frequency bandwidth being used, the more precise is the gain. The ratio of resistors in the op amp circuit more closely defines the gain.