Key benefit of the R/2R ladder DAC architecture Compared with a binary-weighted-resistor DAC, what is the principal advantage of the R/2R ladder approach?

Introduction / Context:
Choosing a DAC topology affects accuracy, cost, and manufacturability. The R/2R ladder dominates discrete implementations because it relaxes resistor tolerance and matching requirements.

Given Data / Assumptions:

• Comparing R/2R ladder versus binary-weighted resistors.
• Equal nominal performance targets (same bit width).

Concept / Approach:
In a binary-weighted DAC, resistor values span wide ratios (e.g., R, 2R, 4R, 8R, …), making precision and matching difficult. The R/2R ladder instead uses only two values (R and 2R) repeatedly, greatly simplifying trimming and keeping parasitics consistent—resulting in better matching and scalability.

Step-by-Step Solution:

Verification / Alternative check:
Review of typical DAC IC datasheets and textbooks consistently cites “only two resistor values” as the R/2R ladder’s major advantage.

Why Other Options Are Wrong:

• Fewer parts: Part count is similar for a given resolution.
• Easier analysis: Analysis simplicity is not the primary advantage.
• Virtual ground eliminated: Many implementations still use an op-amp summing node at virtual ground.

Common Pitfalls:

• Confusing lower parts variety with lower part count.

Final Answer:
It uses only two different resistor values.