Question
What is the purpose of a low-pass filter used at the output of a digital-to-analog converter?
Answer Options
- A) Lower the input bandwidth to increase the effective resolution
- B) Improve accuracy by removing out-of-sequence codes from the input
- C) Remove spurious sampling artifacts from the output signal
- D) All these choices are correct
Correct Answer: C
Explanation
A Digital-to-Analog Converter (\text{DAC}) creates an analog output signal by taking discrete digital samples and holding their voltage level until the next sample is converted (a ‘zero-order hold’). This process results in a stepped, or stair-stepped, analog waveform rather than a smooth sine wave.
The sharp, sudden voltage steps in this stair-stepped waveform contain significant high-frequency energy outside the band of the intended signal (quantization and sampling noise). The purpose of the low-pass filter (often called a reconstruction or anti-alias filter) used at the output of a \text{DAC} is to remove spurious sampling artifacts from the output signal, smoothing the steps and leaving only the clean analog signal component.
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