Transistor Packages

Transistor Outline Package

TO-92 Terminal identification The pinout is as shown to the right. Not all transistors use this pin out, see the pic of the transistor below. The United States uses this type or pin out. Some japanese BJTs use the other style pin out. Check the data sheet to confirm the pin out. It's common for devices to switch pin function. Normally dash numbers changes when pins move. FETs may also be found in this package. Of course FETs having their own pin out.

TO-92 Plastic Body

TO-92 is a through-hole device in a plastic case.
Terminal identification [BJT]; Pin 1 Emitter, Pin 2 Base, Pin 3 Collector.
Terminal identification [Shunt Regulator]; Pin 1 Reference, Pin 2 Anode, Pin 3 Cathode.
Note the location of the flat portion of the case to the pins.

Press-fit Aluminum heat sinks are available for the TO-92 case.
The heat sinks are either slip-on of clip-on heat sinks,
and are some what large compared to the size of the TO-92 body.
The size of the heat sink has a lot to do with the TO-92's plastic body.

The generic dimensions of the TO-92 package include the following:
Body width; 4.58mm +0.25, -0.15mm. Body height; 4.58mm +/-0.20mm.
Lead length 14.47mm +/-0.40mm. Lead width 0.46mm +/-0.10mm.
Lead spacing; 1.27 +/- 0.20mm, 1.02mm from the flat face of the component.

Types of Transistor cases; Transistor and FET Packages.
Manufacturers of FETs and BJTs [Transistor Manufacturers]
How to Derate Transistors [Design Guidelines].

Commercial part numbers using a TO-92 package; BC556, BC557, BC558, BC559, BC560, BC171. A TL431 shunt regulator in a TO-92 .
No MIL spec parts use the TO-92 Transistor because of the plastic package.
No derating curve is listed for a transistor in a TO-92 package.
As a general rule military specifications will define metal or ceramic parts and components.

Note that the leads may come straight or ordered [purchased] formed or bent as shown in the BC171 picture to the left.

Many common parts use this package, including; 2N3904, MPS2222, 2N4401 and MPF102 transistors. Note that the 2N2222 is known as the MPS2222A, or PN2222 in this package [among other names].

Editor note; Any time a commercial part number is provided as a device using a particular package, that part number is just an example. As the same part [perhaps with a slightly different part number] may also be available in a completely different package. For instance the generic part, 2N2222, may also be purchased as a SOT-23 [as MMBT2222A] or SOT-223 [as PZT2222] package.

TO-92 Plastic Body TL-431