仪表放大器设计指南 第三版 01.pdf

Chapter-1: IN-AMP BASICS 第一章：第一章：仪表放大器基本原理仪表放大器基本原理 第一章第一章：：仪表放大器基本原理仪表放大器基本原理 1. INTRODUCTION 简介简介 简介简介 Instrumentation amplifiers (in-amps) are sometimes misunderstood. Not all amplifiers used in instrumentation applications are instrumentation amplifiers, and by no means are all in-amps used only in instrumentation applications. In-amps are used in many applications, from motor control to data acquisition to automotive. The intent of this guide is to explain the fundamentals of what an instrumentation amplifier is, how it operates, and how and where to use it. In addition, several different categories of instrumentation amplifiers are addressed in this guide. 仪表放大器经常被误解。并非所有用在仪器仪表应用中的放大器都是仪表放大器；也绝非所有仪表 放大器只能应用于仪器仪表应用中。仪表放大器应用于多种应用领域，从马达控制到汽车业的数据 采集，等等。本文目的就是解释什么是仪表放大器、仪表放大器如何工作、又如何应用，等等一系 列基础知识。此外，本文附有不同种类的仪表放大器供查询。 2. IN-AMPS vs. OP AMPS: WHAT ARE THE DIFFERENCES? 仪表放大器仪表放大器 运算放大器：运算放大器：区别何在区别何在？？ 仪表放大器仪表放大器 运算放大器运算放大器：：区别何在区别何在？？ An instrumentation amplifier is a closed-loop gain block that has a differential input and an output that is single-ended with respect to a reference terminal. Most commonly, the impedances of the two input terminals are balanced and have high values, typically 109 Ω, or greater. The input bias currents should also be low, typically 1 nA to 50 nA. As with op amps, output impedance is very low, nominally only a few milliohms, at low frequencies. 仪表放大器为闭环增益模块，为差动输入、单端输出（相对于参考端）。通常，两个输入端阻抗平 衡，并且为高阻输入，典型值为 109 Ω 甚至更高；输入偏置电流低，典型值 1nA ~ 50nA ；输出阻 抗极低，如同运算放大器，在低频范围内一般只有数 m Ω。 Unlike an op amp, for which closed-loop gain is determined by external resistors connected between its inverting input and its output, an in-amp employs an internal feedback resistor network that is isolated