By David Herres
典型的现实现象（大多数传感器输出，空气压力变化中的声学信息，温度波动等）是模拟的，而不是数字本质上。如果转换为电信号，它们将在滑动刻度上连续变化，而不是以离散步骤，二进制或其他方式进行编码。
If digital processing and memory are to be used, the analog information must first be digitized. This takes place via an analog-to-digital converter (ADC), as outlined in a上一篇文章。已经开发出有效的方法以适合应用程序的速度和解决方案来完成此过程。
在存储器中处理和存储后，必须将挖掘信息转换回模拟形式。（这是具有讽刺意味的，因为在个体人类中，信号必须再次转换为数字形式，然后我们的神经元网络可以将数据处理并将数据委托到人类记忆。）
The device that accomplishes the conversion is known as a digital-to-analog converter (DAC). It can be implemented either within an IC or as a discrete device, as represented by a high-performance oscilloscope.
A very basic DAC is the pulse-width modulator, frequently appearing as part of a variable-frequency ac motor drive (VFD). A VFD varies the speed of ac motors (usually three-phase induction) in response to changes in the width of electrical pulses synthesized within the control equipment.
脉冲密度转换用于过采样和插值DAC。一个例子是三角洲 - 西格玛DAC。最终结果是，噪声已从低频区域转移到没有问题的较高频率区域。
A very fast DAC is the binary-weighted device, but accuracy is less than required by many applications, and the expense for a high-resolution device may be prohibitive due to the large number of components required.
The R-2R ladder DAC is noteworthy because it is inexpensive and simple to manufacture since it needs only two resistor values. In fact, by means of parallel or series connections, a single resistor value will suffice. Moreover, regardless of the number of bits, the output impedance is consistently equal to the value of the resistor chosen, which simplifies filtering in down-stream analog circuitry. Superposition and Thevenin Equivalent circuit analysis can be applied to make sense of this DAC. These theorems simplify Ohm’s law calculations and make possible determination of the output impedance.
The thermometer-coded DAC consists of a resistor for every possible digitization value. The device is characterized by exceptional speed and accuracy but its high cost precludes most applications.
混合DAC在单个集成电路中结合了两个或多个设计，因此这是一种广泛使用的解决方案。由于全球使用的DAC数量越来越大，我们可以期望这些设备的成本进一步下降。
帖子Basics of digital-to-analog converters首先出现Test & Measurement Tips。
Filed Under:Test & Measurement Tips
