1N21B

The 1N21B is a point contact diode from TE Connectivity, historically used in applications such as police radar warning receivers and harmonic mixers. Its construction is similar to a "cat's whisker" diode, requiring careful handling for optimal performance. Originally, these microwave cartridge diodes were made with a specific polarity convention, but later versions allowed for polarity selection.

This diode features axial termination and comes in a cartridge package. The point contact construction is notable for its ability to rectify RF signals at low power levels without requiring bias, due to curvature in its I-V curve at zero volts bias. While specific electrical ratings are not detailed here, its design points towards applications in RF detection and mixing.

Semiconductor processing advancements were significantly driven by the need to improve microwave diodes like the 1N21 family. This historical context highlights the importance of such components in the early development of semiconductor technology.