Difficulty: Easy
Correct Answer: Incorrect
Explanation:
Introduction / Context: DACs translate numeric codes into voltages or currents. While the output is an electrical (analog-domain) quantity, practical DACs produce discrete step changes with finite settling time, glitch energy, and update rate. The statement claims the output is “truly” analog; we must interpret this against signal theory and hardware realities.Given Data / Assumptions:
Concept / Approach: A stand-alone DAC output is piecewise-constant: it jumps in quantized steps at update instants, then holds. Although the amplitude is continuous within tolerance (not logic-level digital), it is not a perfectly continuous-time, band-limited analog waveform. To obtain a smooth analog signal, designers often follow the DAC with a reconstruction (low-pass) filter that removes images/steps and approximates the desired waveform.Step-by-Step Solution:
Recognize zero-order hold: output remains constant between updates.Account for quantization: smallest change is 1 LSB; output is stair-stepped.Note dynamics: finite-time settling and glitches further deviate from “ideal continuous.”Verification / Alternative check:
Oscilloscope observation shows discrete steps; adding a low-pass filter yields a smoother waveform closer to “truly analog.”Why Other Options Are Wrong:
Correct: Overstates the purity of the analog nature; steps contradict “truly.”True only after a reconstruction filter: This is a useful nuance but the statement as given (without filter) should be judged false.Depends solely on word length: Resolution helps but cannot eliminate discrete updates without filtering.Common Pitfalls:
Equating “not digital logic levels” with “perfect analog.”Ignoring sample-and-hold and reconstruction requirements of DAC systems.Final Answer:
Incorrect
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