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 BJT circuit shown, beta of the PNP transistor is 100 . Assume $V_{B E}=-0.7 \mathrm{~V}$. The voltage across $R_C$ will be 5 V when $R_2$ is $\_\_\_\_$ $\mathrm{k} \Omega$. (Round off to 2 decimal places)

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)

A CMOS Schmitt-trigger inverter has a low output level of 0 V and a high output level of 5 V . It has input thresholds of 1.6 V and 2.4 V . The input capacitance and output resistance of the Schmitt trigger are negligible. The frequency of the oscillator shown in the figure is $\_\_\_\_$ Hz. (Round off to 2 decimal places)