R/2R ladder DAC advantage: Compared with a binary-weighted resistor DAC, what is the primary practical advantage of the R/2R ladder topology that makes it scale well to higher bit counts?

Introduction / Context:Two common DAC resistor topologies are binary-weighted and R/2R ladder. Designers often prefer the R/2R ladder for medium-to-high resolutions due to manufacturability and matching considerations.

Given Data / Assumptions:

• We compare required component precision and scalability as bit width increases.
• Both topologies can be implemented with switches and an op-amp summing node.

Concept / Approach:Binary-weighted DACs need resistor values in powers of two (R, 2R, 4R, …), causing wide spreads and matching difficulties. The R/2R ladder uses only two values (R and 2R), enabling tight ratio matching with standard resistor networks, improved yield, and predictable performance as N grows.

Step-by-Step Solution:Identify component set for binary-weighted: many distinct values → matching challenges.Identify component set for R/2R: only R and 2R → easier trimming and layout.Conclude the primary advantage is “only two resistor values,” improving scalability.Secondary benefits follow: better monotonicity and linearity for a given tolerance class.

Verification / Alternative check:Commercial precision DAC ICs frequently adopt ladder or current-steering architectures, reflecting manufacturability advantages.

Why Other Options Are Wrong:Fewer parts (option B) is not generally true; ladder networks can use similar counts.

Analysis ease (option C) is subjective and not the main reason.

Virtual ground (option D) is common in op-amp based DACs; not eliminated by R/2R per se.

No precision reference (option E) is false; DACs need a stable reference.

Common Pitfalls:Assuming absolute accuracy follows from resistor count; temperature coefficients and switch resistance still matter.

Final Answer:It only uses two different resistor values.