Semiconductor Electronics: Materials, Devices and Simple Circuits — NCERT Solutions

In an unbiased p-n junction, holes diffuse from the p-region to the n-region because the hole concentration is higher in the p-region than in the n-region. Diffusion occurs due to the concentration gradient.

On applying forward bias to a p-n junction, the external voltage is opposite to the built-in potential, so the depletion layer width decreases and the barrier height is reduced. Hence, it lowers the potential barrier.

In half-wave rectification, only one half-cycle of the input appears at the output, so the output frequency is the same as the input frequency:

• Input frequency = $50\,\text{Hz}$
• Half-wave output frequency = $50\,\text{Hz}$

In a full-wave rectifier, both half-cycles are used, so the output frequency becomes twice the input frequency:

• Full-wave output frequency = $2 \times 50 = 100\,\text{Hz}$