Bridging the Divide (Part 1): DAC Introduction
June 21, 2010 | Paul Buckley | 222900832
Bill McCulley, Applications Engineer, National Semiconductor, examines basic DAC operation, key definitions, together with common DAC topologies.
Page 1 of 8The best of what we are and hold as true: Always it is by bridges that we live."
Philip Larkin, British poet
Our world is not a digital environment of absolutes. The electrical signals of the real world are not made of logical highs and lows, or zeros and ones. These signals are analog and they meander within a range of voltages or currents.
The purpose of the Digital to Analog Converter (DAC) is to convert digital data into an analog signal. The digital data may originate from a microprocessor, ASIC, or FPGA, but at some point requires conversion to an analog signal to have impact on the real world. Whether the system uses an audio amplifier, an LED indicator, or a motor driver, the final signal will be analog in nature.
The DAC serves as that bridge to transfer a digital signal into the analog domain and hopefully ends with an accurate and true representation of the signal! As an important part of many electronic systems, it is good to learn about the fundamentals of the DAC.
This first article covers basic DAC operation and key definitions, along with common DAC topologies. The second article will discuss the implementation of DACs, along with issues such as errors and noise. The final article will review two important DAC applications: calibration and motor control.
Since the time of the Nyquist-Shannon sampling theorem, engineers have developed and used DACs, but it is only the past 25 years that monolithic DACs have become widely available. According to the Nyquest-Shannon sampling theorem, any sampled data can be reconstructed perfectly - provided it meets bandwidth and Nyquest criteria (Ref 1). So, with proper design a DAC can reconstruct sampled data in your application with precision.
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