Question

Figure below shows a circuit for implementing an 8-bit Digital-to-Analog converter (DAC) using two identical 4-bit DAC's with equal reference voltage. Assume that $b_0$ represents LSB, $b_7$ MSB and the opamp is ideal. The obtain correct analog values corresponding to an 8-bit DAC at the output $V_0,$ the value of resistor R is

Answer 1

Since the DAC output of $2^{nd}$ DAC (higher byte) $V_{02}$ must be amplified 16 times more than $V_{01}$is amplified in order to get correct output so R must be $\frac{1}{16}\times 8k\Omega$
$R=\frac{8}{16}=0.5k\Omega$