The TO-92 is a widely-used style of transistor enclosure construction. The case is often made of epoxy or plastic, and offers compact size at a very low cost.
Contents |
The JEDEC TO-92 descriptor is derived from the original full name for the package: Transistor Outline Package, Case Style 92.
The case is molded around the transistor elements in two parts; the face is flat, bearing a machine-printed part number.
The back is semi-circularly-shaped. By looking closely from the top, one can observe the seam where the two halves are molded together.
The leads protrude from the bottom of the case. When looking at the face of the transistor, the leads are commonly configured from left-to-right as the emitter, base, and collector for 2N series (JEDEC) transistors, however, other configurations are possible, such as emitter, collector, and base commonly used for 2S series (Japanese) transistors.
The leads coming out of the case are spaced 0.05" (1.27 mm) apart. It is often convenient to bend them outward to a 0.10" (2.54 mm) spacing to make more room for wiring. Units with their leads pre-bent may be ordered to fit specific board layouts, depending on the application. Otherwise, the leads may be bent manually; however, care must be taken as they can break easily.
The main disadvantage of this style of case is the lack of heat sinking.
More often than not, however, the disadvantages concerning accidental destruction are greatly outweighed by the small size and low cost of producing these units.