Analog Electronics for Measuring Systems

2Amplification and Amplifiers

2.1. Introduction

In Chapter 1, we described a certain number of sensors, as well as the conditioning circuit used to obtain a voltage as an electrical representation of the measurand. Now, this voltage should be somehow treated: in most cases, it should be amplified, and often filtered. This chapter is devoted to the amplification of low-frequency signals and it is particularly focused on circuits based on operational amplifiers. We will therefore begin by briefly describing the working principles of operational amplifiers: in particular, we will focus on some parameters specified in the data sheets quantifying their limits and non-idealities. We will describe here the so-called voltage-feedback operational amplifier (often just called operational amplifier), frequently adopted in low-frequency circuits. A different element, the current-feedback operational amplifier, bears some resemblance to it, but as its use is more specific, it will not be described here. We will then give an overview of differential amplifiers, in particular the instrumentation amplifiers. The name of those circuits reflects their widespread use in instrumentation… The end of the chapter will be devoted to insulation amplifiers, which are very useful when security or electromagnetic compatibility issues are of primary importance.

There are a lot of very good textbooks that develop the matter presented here in detail. One of them is, of course [ASC 03], also cited in the ...