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 ______

In the circuit shown below the op-amps are ideal. Then V_out in Volts is

The circuit shown is a

Consider the following circuit using an ideal Op-Amp. The I-V characteristics of the diode is described by the relation $$$I = {I_0}\left[ {{e^{{V \over {VT}}}} - 1} \right], where \,{V_T}\,\, = \,\,25mV,{I_0}\,\, = 1 \mu {\rm A}$$$

and V is the voltage across the diode (taken as positive for forward bias). For an input voltage $${V_i}\,\, = \,\, - 1V,$$ the output voltage V₀ is