Question

What is the analog output for a 4-bit R-2R ladder DAC when input is (1000)₂, for V_ref = 5 V?
1. 2.3333 V
2. 2.4444 V
3. 2.5556 V
4. 2.6667 V

Answer 1

Correct Answer - Option 4 : 2.6667 V

Concept:

\(step\;size = {\rm{\Delta }} = \frac{{{V_{ref}}}}{{{2^n} - 1}}\) 

n is the number of bits

V_ref is the reference voltage

Output of DAC is,

V_o = Δ × (Decimal equivalent of binary)

Calculation:

V_ref = 5 V

No. of bits = 4

Binary equivalent = 1000

Decimal equivalent = 8

Step size \(= {\rm{\Delta }} = \frac{5}{{{2^4} - 1}} = \frac{1}{3}\)

\({V_o} = \frac{1}{3} \times 8 = 2.6667\;V\)