Semiconductor, the most special is its unilateral conductivity. "Semiconductor" got its name from this. In other words, the current can only flow in one direction, but not in the opposite direction. Crystals used in semiconductors are usually made of germanium or silicon. Because of the low cost of silicon material, silicon tube is the most widely used.

A crystal diode made of a semiconductor with unilateral conductivity can change alternating current into direct current. Used in electronic circuits, it can play the role of detection, shaping, damping and voltage stabilization.

Several transistors and resistors form a functional circuit and are integrated into a chip, which is called an integrated circuit. For example, there are thousands of transistors in a computer processor (CPU)!