In the linear regulator circuit shown, the base to emitter voltage $V_{B E}$ of the BJT is 0.6 V . The Zener diode clamps the base voltage to 5.4 V . Ignore the biasing current of the Zener diode and BJT. The maximum possible efficiency of the regulator circuit is

$\_\_\_\_$ % (Round off to one decimal place)

For the circuit shown below with ideal diodes, the output will be

In the circuit shown, a 5 V Zener diode is used to regulate the voltage across load $R_0$. The input is an unregulated DC voltage with a minimum value of 6 V and a maximum value of 8 V . The value of $R_s$ is $6 \Omega$. The Zener diode has a maximum rated power dissipation of 2.5 W . Assuming the Zener diode to be ideal, the minimum value of $R_0$ is $\_\_\_\_$ $\Omega$.

In the circuit shown, the input $V_i$ is a sinusoidal AC voltage having an rms value of $230 \mathrm{~V} \pm 20 \%$. The worst case peak-inverse voltage seen across any diode is $\_\_\_\_$ V. (Round off to 2 decimal places)