ADC/DAC(4)- 什么是DAC以及DAC的应用

2018-12-06 10:44:55 来源:电路设计技能
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苏老师时不时要让大家阅读一些英文的资料,养成用英文学习和阅读的习惯,毕竟这个行业全球最前沿、最权威的信息都是英文的。今天借“elprocus”上面的一篇综述性的文章介绍一下什么是DAC、DAC的基本构成以及DAC的一些典型应用,有任何问题可以通过留言或者在我们的技术交流群里进行交流,我们明天再说说DAC的一些选型要领。
 
在文章中主要介绍了最常用的两种DAC构成结构,其实我们在很多场景下会采用PWM(脉宽调制)+低通滤波来实现数字量到模拟量的转化,比如开关稳压,关于PWM我也会在以后的文章中专门讲一下。
 
About Digital to Analog Converter (DAC) and Its Applications
Why we need data converters? In the real world, most data are available in the form of analog in nature. We have two types of converters analog to digital converter and digital to analog converter. While manipulating the data, these two converting interfaces are essential to digital electronic equipment and an analog electric device which to be processed by a processor in order produce required operation.
 
For example, take the below DSP illustration, an ADC converts the analog data collected by audio input equipment such as a microphone (sensor), into a digital signal that can be processed by a computer. The computer may add sound effects. Now a DAC will process the digital sound signal back into the analog signal that is used by audio output equipment such as a speaker.
 
语音信号处理
 
Digital to Analog Converter (DAC)
Digital to Analog Converter (DAC) is a device that transforms digital data into an analog signal. According to the Nyquist-Shannon sampling theorem, any sampled data can be reconstructed perfectly with bandwidth and Nyquist criteria.
 
A DAC can reconstruct sampled data into an analog signal with precision. The digital data may be produced from a microprocessor, Application Specific Integrated Circuit (ASIC), or Field Programmable Gate Array (FPGA), but ultimately the data requires the conversion to an analog signal in order to interact with the real world.
 
基本的数字/模拟转换器
 
D/A Converter Architectures
There are two methods commonly used for digital to analog conversion: Weighted Resistors method and the other one is using the R-2R ladder network method.
DAC using Weighted Resistors method
 
The below shown schematic diagram is DAC using weighted resistors. The basic operation of DAC is the ability to add inputs that will ultimately correspond to the contributions of the various bits of the digital input. In the voltage domain, that is if the input signals are voltages, the addition of the binary bits can be achieved using the inverting summing amplifier shown in the below figure.
 
二进制权重的电阻DAC
 
In the voltage domain, that is if the input signals are voltages, the addition of the binary bits can be achieved using the inverting summing amplifier shown in the above figure.
 
The input resistors of the op-amp have their resistance values weighted in a binary format. When the receiving binary 1 the switch connects the resistor to the reference voltage. When the logic circuit receives binary 0, the switch connects the resistor to ground. All the digital input bits are simultaneously applied to the DAC.
 
The DAC generates analog output voltage corresponding to the given digital data signal. For the DAC the given digital voltage is b3 b2 b1 b0 where each bit is a binary value (0 or 1). The output voltage produced at output side is
 
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