DAC error terminology: “When a DAC’s measured step sizes deviate from the ideal 1 LSB step size, the error is called nonlinearity.” Judge this statement.

Introduction / Context:
Precision DACs are characterized by several error metrics. Distinguishing offset, gain, differential nonlinearity (DNL), and integral nonlinearity (INL) is fundamental for specifying accuracy and control-loop stability. The question targets the concept of nonlinearity as it relates to step size deviations.

Given Data / Assumptions:

• Ideal step size = 1 LSB in a nominally linear DAC.
• Measured step sizes may vary due to mismatch and circuit nonidealities.
• We focus on deviations from ideal steps and their classification.

Concept / Approach:
DNL quantifies how much each individual code-to-code step differs from 1 LSB. INL quantifies cumulative deviation of the transfer curve from a straight line (best-fit or endpoint). Thus, “deviation of the measured step size from the ideal step size” directly describes DNL, which is a form of nonlinearity. Therefore, the statement is correct in the general sense that such deviations fall under nonlinearity errors.

Step-by-Step Solution:

Verification / Alternative check:
Datasheets list DNL and INL separately under “nonlinearity.” Step size variation appears explicitly in DNL plots.

Why Other Options Are Wrong:

• Incorrect: Conflicts with standard definitions.
• Offset error: A uniform shift of the whole curve, not step deviation.
• Ambiguous due to reference: Reference drift shifts the scale but does not define nonlinearity by itself.

Common Pitfalls:
Confusing gain error (slope) and offset error with nonlinearity; assuming INL alone captures all step deviations.

Final Answer:
Correct