GATE EC 2014 Set 1 Q37 — Op-amp Circuits

In the voltage regulator circuit shown in the figure, the op-amp is ideal. The BJT has $V_{BE} = 0.7\:V$ and $\beta = 100,$ and the zener voltage is $4.7\:V.$ For a regulated output of $9\:V,$ the value of $R$ (in $\Omega)$ is ______.