《数字电子技术基础》由会员分享，可在线阅读，更多相关《数字电子技术基础（55页珍藏版）》请在金锄头文库上搜索。
1、第十一章 数-模和模-数转换11.1 概述11.2 D/A转换11.3 A/D转换Evaluation only.Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.Copyright 2004-2011 Aspose Pty Ltd.11.1 概述一个计算机控制系统的框图如图11.1.1所示
2、。1.用途：Evaluation only.Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.Copyright 2004-2011 Aspose Pty Ltd.11.1 概述图11.1.2为一个温度控制系统：传感器放大器A/D 转换微型计算机控制 对象D/A 转换电加热炉热电偶执行机构图
3、11.1.2温度时间 Evaluation only.Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.Copyright 2004-2011 Aspose Pty Ltd.2、主要性能指标转换精度和转换速度11.1 概述3、概念及分类 （1） D/A转换器：将数字信号转换成模拟信号的过程称
4、为数/模转换 （Digital to Analog），实现的电路称为D/A转换器， 简写成DAC（DigitalAnalog Converter）。 (2)A/D转换器 ：将模拟信号转换成数字信号的过程称为模/数转换 （Analog to Digital），实现的电路称为A/D转换器， 简写为ADC（AnalogDigital Converter）。Evaluation only.Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Created with Aspose.Slides f
5、or .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.Copyright 2004-2011 Aspose Pty Ltd.11.2 D/A转换器数字量是用代码按位数组合起来表示的D/A转换器是由数码寄存器、模拟电子开关电路 、解码电路、求和电路及基准电压及部分组成。Evaluation only.Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Created with Aspose.Slides
6、 for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.Copyright 2004-2011 Aspose Pty Ltd.图11.2.24位权电阻网络D/A转换器由权电阻网络、4个电子模拟 开关和1个求和放大器组成。11.2.1 权电阻网络D/A转换器1.组成 ：Evaluation only.Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Created with Aspose.Slide
7、s for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.Copyright 2004-2011 Aspose Pty Ltd.Evaluation only.Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty
8、Ltd.Copyright 2004-2011 Aspose Pty Ltd.2.输出电压的计算：由于V V0， 故各电流为输出电压为Evaluation only.Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.Copyright 2004-2011 Aspose Pty Ltd.取RF
9、R / 2，则输出 电压为Evaluation only.Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.Copyright 2004-2011 Aspose Pty Ltd.上式标明，输出的模拟电压与输入的数字量Dn成正比。注：1.若VREF取正值，则输出电压为负值。若想输出 电压为正值
10、，可以将VREF取负值。2. 此电路的优点是电路结构简单，所用的电阻元件少 。缺点是各个电阻的阻值相差较大，输入数字量的位 数越多，差别就越大，故很难保证电阻的精确度。Evaluation only.Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.Copyright 2004-2011 A
11、spose Pty Ltd.11.2.2 倒T形电阻网络D/A转换器为了克服权电阻网络D/A转换器电阻阻值相差太 大的缺点，改进电路为倒T型电阻网络D/A转换器图11.2.4Evaluation only.Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.Copyright 2004-201
12、1 Aspose Pty Ltd.RRRR图11.2.5Evaluation only.Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.Copyright 2004-2011 Aspose Pty Ltd.总的电流为RRRR图11.2.5Evaluation only.Evaluation
13、 only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.Copyright 2004-2011 Aspose Pty Ltd.由于故输出电压为Evaluation only.Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile
14、5.2.0.0.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.Copyright 2004-2011 Aspose Pty Ltd.对于n位输入的倒T形电阻网络D/A转换器，在求和 放大器的反馈电阻为R时，其输出的模拟电压为上式说明输出的模拟电压与输入的数字量成正比，其 其输出公式与权电阻网络D/A转换器相同。11.2.2 倒T形电阻网络D/A转换器Evaluation only.Evaluation only. Created with As
15、pose.Slides for .NET 3.5 Client Profile 5.2.0.0.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.Copyright 2004-2011 Aspose Pty Ltd.图11.2.6为采用倒T型电阻网络的单片集成D/A转换器 CB7520(AD7520)的电路。11.2.2 倒T形电阻网络D/A转换器其输入为10位二进制数，采用CMOS电路构成的模拟开关 。图11.2.6Evaluation only
16、.Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.Copyright 2004-2011 Aspose Pty Ltd.输出电压为图11.2.6Evaluation only.Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.Copyright 2004-2011 Aspose Pty Ltd.注：在使用CB7520时需要外接运算放大器，反
