DAC behavior — The requirement that increasing (or decreasing) the digital code by one step causes exactly one corresponding step change at the output is called what?
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Aresolution
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Blinearity
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Cmonotonicity
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Daccuracy
Answer
Correct Answer: monotonicity
Explanation
Introduction / Context: When converting digital codes to analog signals, a key quality is whether the output moves predictably with each code step. Control systems and audio applications especially require that one code increment never produces a backward or erratic jump in the output.Given Data / Assumptions:
- We are discussing a DAC operating over successive codes.
- Focus is on the relationship between adjacent codes.
- Ignore absolute gain/offset errors for this definition.
Concept / Approach: Monotonicity means the output never decreases when the input code increases (and never increases when the code decreases). A stricter interpretation in many specs is that each single-code change results in exactly one step in the correct direction with no reversals. Missing codes or large DNL errors can break monotonicity.Step-by-Step Solution:
Consider adjacent codes k and k+1.A monotonic DAC guarantees V_out[k+1] ≥ V_out[k] for an increasing sequence.Design goal: DNL ≤ 1 LSB ensures no missing codes and preserves monotonicity.Verification / Alternative check:
Datasheets list monotonicity and DNL; monotonicity is often guaranteed over temperature for precision DACs.Why Other Options Are Wrong:
resolution: Smallest code step size (LSB), not the behavior of steps.linearity: Deviation from an ideal straight line (INL), not step-by-step guarantee.accuracy: Overall closeness to ideal value; broader than step behavior.Common Pitfalls:
Confusing monotonicity with linearity; a DAC can be monotonic yet non-linear.Final Answer:
monotonicity