Diagnosing a DAC output that is uniformly shifted Referring to the shown D/A converter output (figure referenced in the original item), what appears to be wrong, and how should the problem be corrected?

Introduction / Context:
D/A converter troubleshooting often starts by distinguishing offset error (uniform vertical shift), gain error (slope error), and nonlinearity (deviation from a straight line). Knowing these signatures speeds diagnosis.

Given Data / Assumptions:

• The staircase/ramp output is uniformly displaced from zero by a constant amount across codes.
• No distortion or code-dependent bowing is reported.

Concept / Approach:
Offset error appears as a constant shift of the entire transfer characteristic. Common causes: op-amp input offset voltage, bias currents with source impedance, or reference/bipolar offset network tolerance. Nonlinearity would show curvature or step irregularity; gain error would change slope.

Step-by-Step Solution:

Verification / Alternative check:
Measure output for code 0 and full-scale; if both are equally shifted relative to ideal, the error is offset, not slope or linearity.

Why Other Options Are Wrong:

• Nothing wrong: A uniform shift is not ideal behavior.
• Nonlinearity: Would not stay parallel to the ideal line.
• Power supply too high: That would more likely affect headroom, clipping, or reference rails, not a consistent offset alone.

Common Pitfalls:

• Misinterpreting a consistent shift as gain error—gain changes slope, not intercept.

Final Answer:
There is an offset error; if no provision is made for adjusting the offset, the op-amp may need to be changed.