PNdioder

PN diodes are electronic devices formed by joining p-type and n-type semiconductor regions to create a PN junction. They allow current to flow readily when forward-biased (p region connected to the positive side), while blocking current under reverse bias, except for a small leakage current or until breakdown occurs. The forward-conducting behavior is essential for rectification and signal processing, whereas the reverse-blocking property provides protection and isolation in circuits.

Construction and structure: A PN junction is created by diffusing dopants into silicon or by growing doped layers during epitaxial deposition. The contact between p and n regions forms a depletion region with an internal electric field that resists carrier movement. The junction's electrical size and capacitance depend on the bias and geometry, and the device can be designed for fast switching or high current handling.

Electrical characteristics: Forward current increases roughly exponentially with applied voltage, described by the diode equation I = I_s (e^{V/(nV_t)} − 1). In reverse bias, the current remains small until breakdown at high reverse voltages. The typical forward voltage drop for silicon diodes is about 0.6–0.7 V at moderate current; germanium diodes exhibit lower drops, around 0.2–0.3 V. Some diodes are optimized for speed with short reverse-recovery times, while others emphasize high voltage or high current capability.

Applications: PN diodes are used for rectification in power supplies, signal demodulation, clamping and limiting circuits, switching and protection roles in digital logic, and RF or audio detection in receivers. Variants include high-speed switching diodes and high-power rectifiers, produced from silicon and other semiconductor materials.

Materials and variants: Silicon is the most common material, though germanium and other semiconductors have been used in specialized applications. PN diodes differ from Schottky diodes, which use a metal-semiconductor junction and exhibit different voltage drops and speed characteristics.