AD/DA conversion
What is the drawback of a binary-weighted resistor DAC, which assigns a different resistor (R, 2R, 4R, ...) to each bit?
- AAs the number of bits grows, the resistor ratio becomes very large, making accurate fabrication difficult
- BIts structure inherently prevents a monotonic output
- CIts conversion speed is very slow
Show answer and explanation
Answer: A. As the number of bits grows, the resistor ratio becomes very large, making accurate fabrication difficult
In a binary-weighted resistor DAC, the ratio between the smallest and largest resistors reaches 2ᴺ⁻¹ for N bits. With more bits, it becomes difficult to match resistors differing by orders of magnitude with high accuracy. The R-2R ladder uses only two resistor values and avoids this problem.
- A. Correct. The large resistor ratio makes accuracy hard to achieve.
- B. With accurate enough resistors, monotonicity can be maintained.
- C. The binary-weighted DAC is simple; slow conversion is not its main drawback.