Question

An 8-bit successive approximation type ADC has a resolution of 30 mV. The digital output for an analog input of 2.86 V is

• A. ${01100000}_2$
• B. ${01011111}_2$
• C. ${01101100}_2$
• D. ${01110011}_2$

Answer 1

The correct option is B

${01011111}_2$

$\text{Analog voltage}=\text{Resolution}\times \text{Digital equivalent}$

$2.86=30mV\times \text{Digital output}$

$\text{Digital output}=\frac{2.86V}{30mV}=95.3$

The step 95 would produce 2.85 V and step 96 would produce 2.88V.

The successive approximation type ADC always produce a final output i.e., a step below the analog input.

$\therefore$ The digital result would be

${95}_{10}={01011111}_2$