The diode given here is connected as a capacitor. A pulse input is given as input to the circuit. The circuit is a RC circuit. During the positive half-cycle, the capacitance starts charging. The capacitance in the diode starts charging from 0 V till the maximum voltage is reached i.e. 5 V. once the input voltage goes to 0 V, the capacitor starts discharging till it reaches 0 V. The time taken to charge the capacitor from 10% to 90% of the maximum value must be calculated. This is the time constant of this system. The time constant of the system is given by ? = 2.2RC. Using this the capacitance value is calculated.