AD/DA conversion

Which correctly describes the "offset binary" code used in ADCs that handle both positive and negative voltages?

  1. AThe MSB alone represents the sign and the remaining bits the magnitude
  2. BNegative full scale is all 0s, positive full scale is all 1s, and 0 V is represented by the middle code
  3. CAll negative values are collapsed into the all-0 code
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Answer: B. Negative full scale is all 0s, positive full scale is all 1s, and 0 V is represented by the middle code

Offset binary assigns 000...0 to the minimum of the input range (negative full scale) and 111...1 to the maximum, with 0 V near the middle code (for example 100...0). It differs from two's complement only by an inverted MSB, and both are commonly used in bipolar-input ADCs.

  • A. An MSB sign with the remaining bits as magnitude is sign-magnitude representation.
  • B. Correct. The whole range is assigned from 0 upward, with 0 V in the middle.
  • C. Collapsing negative values into a single code would lose information.
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More AD/DA conversion questions

  1. How many output levels can an 8-bit AD converter represent?
  2. What sampling frequency is needed to sample an analog signal containing components up to 20 kHz without aliasing?
  3. Which is a characteristic of a flash AD converter?
  4. Which correctly describes the operation of a successive-approximation (SAR) AD converter?
  5. What is the maximum quantization error of an ideal AD converter? (LSB: the voltage corresponding to one least significant bit)