Electronics - Analog and Digital Converters - Discussion

Discussion Forum : Analog and Digital Converters - General Questions (Q.No. 2)
2.
A 4-bit R/2R digital-to-analog (DAC) converter has a reference of 5 volts. What is the analog output for the input code 0101.
0.3125 V
3.125 V
0.78125 V
–3.125 V
Answer: Option
Explanation:
No answer description is available. Let's discuss.
Discussion:
34 comments Page 2 of 4.

Manjeet said:   1 decade ago
Vo = 5(Vi/16)

= 5(5/16)

= 1.5625
4-bit R/2R digital-to-analog....

Here what about R/2R...?

I think 1.5625 x 2 = 3.125V

SUMIT SHAH said:   1 decade ago
Main equation is,
Vo= Vref * (b0*2^(-1)+b1*2^(-2)+....)
Vo= 5 * (1*2^(-1)+0*2^(-2)+1*2^(-3)+0*2^(-4))
Vo=3.125V

Ashu said:   1 decade ago
Vo = 5(0/16+1/8+0/4+1/2).
Vo = 3.125.

Vidya said:   1 decade ago
Vout = Resolution * Decimal equivalent of given No.
Where Resolution = Vref/(2^n)-1
Resolution = 5/(2^4)-1 = 5/7
And dec No = 5

So answer = 25/7 = 3.125.
(1)

Vaishnavi murugan said:   1 decade ago
Formula = [Vref/(2^n)] {msb bit * 2^0 + next bit * 2^1 + next bit * 2^2 + lsb bit * 2^3}.

Where n = no of bit,

Solution:

Vref = 5v;
n = 4;

=> (5/(2^4)) {0*0 + 1*2 + 0*4 + 1*8}

=> (5/16) {0 + 2 + 0 + 8}

=> (0.3125) {10}

=> 3.125.

Answer => 3.125.

GOPAL said:   1 decade ago
@Nirja.

Formula = (Vref/2^N)(dec equivalent of i/p).

N- is number of significant bits (here 3 as msb is 0).

Here 0101 = 101 hence consider 3 bit.

Therefore,
Vo = 5(Vi/8) = 3.12.

Shah said:   1 decade ago
MOST EASY METHOD:

V(0ut) = (Vi/8)*digital input.

Nitu said:   1 decade ago
Vo = (Rf/R)(Vref)(Do/16+D1/8+D2/4+D3/2).

Nisha said:   1 decade ago
In case of inverting, Vo = -1.5625 V.

In case of non-inverting, Vo = 3.125V.

So the given answer is correct.

Sarika rajesh banda said:   10 years ago
Yes,

Actual answer is 1.5625 volts.

Given in the sum is reference voltage = 5v, and resolution = 4.

So voltage per lsb = vref/2^n = 5/2^4 = 0.3125 v/lsb.

Therefore = 0101 in decimal is 5 = 5*0.3125 = 1.5625.


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