An antifuse functions in an opposite manner as the fuse (which allows conduction up to a certain level). Once that level is exceeded, it opens the conduction path, stopping current flow. An antifuse also allows conduction up to a certain level. However, once that level is exceeded, it closes the conduction path, allowing low resistance current flow through the antifuse.

Antifuses are commonly used in programmable read-only memory (PROM). Each bit contains both a fuse and an antifuse and is programmed by triggering one of the two. This programming, performed after manufacturing, is permanent and irreversible.

The antifuse is usually triggered using an approximately 5 mA current. With a poly-diffusion antifuse, the high current density creates heat which melts a thin insulating layer between polysilicon and diffusion electrodes, creating a permanent resistive silicon link.

Antifuses are also seen in christmas tree lights. each bulb has an antifuse (with a fairly high resistance) across it. when the bulb blows the voltage accross the anitfuse rises signifiantly and the antifuse shorts out the blown bulb allowing the series cuircuit to keep functioning.