JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B. Tech III BASIC ELECTRONICS Previous Question Paper (February - 2022 - R13)

A full-wave rectifier converts both halves of the AC input cycle into a pulsating DC output. When a π-filter (consisting of an input capacitor C1, a series inductor L, and an output capacitor C2) is connected to the rectifier output, it significantly reduces ripples. The input capacitor C1 bypasses the AC components to ground, the inductor L blocks AC and allows DC to pass due to its high reactance to ripple frequencies, and the output capacitor C2 provides further smoothing by shunting remaining AC components.

The ripple factor (γ) for a π-filter is derived based on the attenuation provided by the filter components. For a full-wave rectifier with a π-filter, the ripple factor is approximately given by:

Where ω is the angular frequency (2πf), L is the inductance, C1 and C2 are the filter capacitances, and R_L is the load resistance. This shows that the ripple factor is inversely proportional to the product of the filter components, making the output significantly smoother than a simple capacitor filter.

A semiconductor diode acts as a switch based on its bias condition. In forward bias, the anode is at a higher potential than the cathode, allowing current to flow with minimal resistance, effectively acting as a closed switch (ON state). In reverse bias, the anode is at a lower potential than the cathode, creating a wide depletion region that prevents current flow, acting as an open switch (OFF state). This switching behavior is fundamental to digital logic circuits and power electronics.