Definition focus – DAC “resolution”: For a digital-to-analog converter, what exactly does the specification “resolution” mean in terms of the smallest change at the output for a one-code increment at the input?
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AIt is the comparison between the actual output of the converter and its expected output.
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BIt is the deviation between the ideal straight-line output and the actual output of the converter.
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CIt is the smallest analog output change that can occur as a result of an increment in the digital input.
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DIt is its ability to resolve between forward and reverse steps when sequenced over its entire range.
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EIt is the converter’s maximum update rate in samples per second.
Answer
Correct Answer: It is the smallest analog output change that can occur as a result of an increment in the digital input.
Explanation
Introduction / Context:Vendor datasheets list several key DAC/ADC parameters: resolution, accuracy, linearity, monotonicity, and speed. Confusing these terms can lead to poor component choices or unrealistic performance expectations.
Given Data / Assumptions:
- An N-bit DAC with full-scale range VFS (or IFS for current output).
- Ideal behavior assumed for defining terms.
- We want the precise meaning of “resolution.”
Concept / Approach:Resolution quantifies the granularity of the DAC's output steps. For an ideal N-bit DAC, 1 LSB = VFS / (2^N). A single increment of the digital input changes the output by one LSB. Other specs describe different behaviors: accuracy (overall error), integral nonlinearity (deviation from the ideal straight line), differential nonlinearity (step size error), monotonicity (no step reversals).
Step-by-Step Solution:Relate the digital code increment (k→k+1) to analog change.Ideal analog step = 1 LSB = VFS / (2^N).Therefore, resolution is the smallest analog output change caused by a 1-LSB input increment.This definition is independent of accuracy or linearity errors.
Verification / Alternative check:Cross-check with any DAC datasheet block: “Resolution: 12 bits; LSB size: Vref/4096.” This directly defines resolution as the minimum step.
Why Other Options Are Wrong:Option A describes absolute accuracy.
Option B describes integral linearity error.
Option D is a loose phrasing of monotonicity, not resolution.
Option E refers to update rate (speed), unrelated to step size.
Common Pitfalls:Equating higher bit count with better accuracy; noise, reference stability, and linearity determine usable resolution (ENOB) in practice.
Final Answer:It is the smallest analog output change that can occur as a result of an increment in the digital input.