In successive approximation ADC offset voltage equal to 1/2 LSB is added to the D/A converter's output. This is done to :
MH SET - 2018, SET Exam - 2018,
Answer: B
The half-LSB offset is added to reduce the maximum quantization error.
Without the offset, a successive approximation converter truncates: every input between two code levels is rounded down, so the error ranges from 0 to almost 1 LSB. Shifting the D/A comparison levels by half an LSB makes the converter round to the nearest level instead, so the error lies between -1/2 and +1/2 LSB and its maximum magnitude halves.
The offset does not change the number of comparisons, so it does not affect speed; it does not add output bits; and it does not widen the input range, since the full-scale code is unchanged.
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