Defining DAC resolution (practical metric): One practical way to express the resolution of a DAC is the ratio of one LSB step size to the full-scale output span. Evaluate this statement.

Difficulty: Easy

Correct Answer: Correct

Explanation:


Introduction / Context:
Resolution can be stated in several complementary ways: in bits (n), in number of distinct codes (2^n), as an absolute LSB voltage/current step, or as a fraction of the full-scale range. Engineers often use the ratio LSB/FS (sometimes expressed as a percentage or parts per million) because it directly links code granularity to the converter’s usable output span.


Given Data / Assumptions:

  • Ideal n-bit DAC with a defined full-scale span (FS).
  • Uniform step size across codes (ignoring DNL/INL for the definition).
  • Full-scale may be specified as Vref or a scaled multiple thereof by the DAC topology.


Concept / Approach:
For an ideal DAC, LSB step size = FS / (2^n). Many texts define “resolution” as 1 in 2^n of full scale, i.e., LSB/FS. Some use (2^n − 1) in the denominator when mapping codes 0…(2^n − 1) over FS; the key point is that resolution can be expressed as the fractional LSB size relative to FS. This is a practical, widely used definition alongside the bit count.


Step-by-Step Solution:

Identify bit resolution n → total codes = 2^n.Relate step to span: LSB ≈ FS / 2^n (ideal case).State resolution as a ratio: LSB/FS = 1 / 2^n (or closely 1 / (2^n − 1)).


Verification / Alternative check:
Datasheets often present both n (bits) and LSB size in volts or microamps; the fractional view is inherent in percent-of-full-scale specifications.


Why Other Options Are Wrong:

“Incorrect”: Conflicts with standard engineering usage.Unipolar/endpoint caveats: The ratio concept applies broadly; sign and endpoint choice do not invalidate it.“Depends solely on Vref”: Vref sets absolute LSB in volts, but the ratio is determined by n and mapping, not by the specific Vref value.


Common Pitfalls:
Confusing resolution (granularity) with accuracy (INL/DNL, gain/offset) and noise; a small LSB does not guarantee accurate outputs.


Final Answer:
Correct

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