Difficulty: Easy
Correct Answer: R/2R ladder D/A converter
Explanation:
Introduction / Context: Two common DAC realizations are the binary-weighted-resistor DAC and the R/2R ladder DAC. Textbook schematics often show a repetitive ladder using only two resistor values (R and 2R), with digital switches steering nodes either to a reference or ground. Recognizing this pattern is essential in converter identification questions, even when a figure is summarized in text.Given Data / Assumptions:
Concept / Approach: The R/2R ladder uses only two resistor values, simplifying matching and scaling. Each additional bit adds one identical section, making the design highly modular. Equal 2R branches ensure that each bit contributes a precisely halved weight relative to the next more significant bit without requiring exponentially small or large resistor values.Step-by-Step Solution:
Identify the repeating R–2R sections and their taps controlled by bit switches.Note that currents from all sections sum at the output node or op-amp summing junction.Conclude that the structure is an R/2R ladder DAC, not a binary-weighted resistor network requiring many resistor values.Verification / Alternative check:
Compare with binary-weighted DACs: those require R, 2R, 4R, 8R, ...; the ladder requires only R and 2R.Why Other Options Are Wrong:
four-bit decoder: A logic device, not an analog converter network.binary-weighted-input DAC: Different topology using many resistor values.four-bit A/D converter: ADCs are measurement devices, not resistor ladders with output summing nodes as shown.Common Pitfalls:
Assuming any ladder of resistors is an A/D; the presence of bit-controlled switches and a summing node indicates a DAC.Final Answer:
R/2R ladder D/A converter
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