Combinational Logic Circuits Questions and Answers

Answer: B

The resolution (the size of one step) of an n-bit ADC is the full scale range divided by \(2^n - 1\) steps.

\[ \begin{aligned} \text{Resolution} = \frac{3\ \text{V}}{2^4 - 1} \\ &= \frac{3}{15} = 0.2\ \text{V} = 200\ \text{mV} \end{aligned} \]

Dividing by 16 instead of 15 would give 187.5 mV, which is not offered, so 200 mV is the intended answer. The values 100, 300 and 400 mV would be 3 V divided by 30, 10 and 7.5, which do not correspond to a 4-bit converter. The answer is option B.

Answer: C

For an N bit straight binary digital to analogue converter the output voltage is the proportionality factor times the decimal value of the binary input.

\[ V_o = K \times (\text{decimal value of input}) \]

The binary input 0010 is 2 in decimal (the bit with weight \(2^1\) is set), and \(K = 1\), so

\[ V_o = 1 \times 2 = 2\ \text{V} \]

The value 1 would be for the input 0001, and 3 for 0011, and 0 for 0000. The answer is 2, option C.