Question

The circuit of DAC is given below. Switch are closed if input bit is 1, otherwise open.

If full scale voltage is to be $V_{out}$ = -4V, then value of $R_F$ would be ______(Answer upto two decimal places).

• A. 8.53

Answer 1

The correct option is A 8.53
The full scale output voltage is given by

$V_0$ = $\frac{-R_f}{8R}\times V_{ref}\times 15$

$-4=\frac{-R_f}{8\times 20k\Omega }\times 5\times 15$

$R_f=\frac{16\times 8}{15}=8.53k\Omega$