TO-18 Transistor Case Package

TO-18 Package

Transistor Can Packages; TO-18 Case style, Metal Can

TO-18 is a through-hole device with a metal lid. Terminal identification; Pin 1 Emitter, Pin 2 Base, Pin 3 Collector. The Collector is internally connected to the case. Note the location of the tab to the pins. Transistor Sockets are available for the TO-18 package and will also work for TO-92, TO-5, TO-72 or TO-39 Devices [which is only slightly larger]. The sockets are PC Mounting of differing sizes [1/4" Diameter X 1/4" High, is one example]. The required Heat Sink would be circular style to slide over the top of the metal can, normally secured with a Thermal Adhesive.

TO-18 Metal Can

TO-18 Physical Measurements

Components that can be purchased in a TO-18 package include a 2N2222A or 2N3960 NPN Transistor, a 2N2646 UJT or 2N4091, 2N4092, 2N4093 FETs.
NPN Low-Power Transistor, 2N2484
PNP Switching Transistor, 2N4029, 2N4209
P-Channel Field Effect Transistor, 2N5114, 2N5115, 2N5116
N-Channel Field Effect Transistor, 2N7002
FET = Lead 1 = source, lead 2 = gate, lead 3 = drain.
Design note; Derating curves for a 2N2222A Transistor in a TO-18 package.
Photo-transistors [lensed TO-18 package], CLT130, CLT131, CLT132 and CLT133
N-Channel FET; 2N4856, 2N4857, 2N4858, 2N4859, 2N4860, 2N4861
FET = Terminal 1; Source, Terminal 2; Drain, Terminal 3; Gate.
N-Channel FET; 2N4091, 2N4092, 2N4093
FET = Terminal 1; Source, Terminal 2; Drain, Terminal 3; Gate.

Design note; The TO-18 package is very common, and in some cases a requirement when designing with military systems compared to other packages. However, when designs do not need the stringent requirements asked for by military designs, then some designers my opt for the cheaper plastic TO-92 package [assuming the device is offered in that package].

Some companies may refer to this as a SOT18, although the JEDEC reference, or more common reference is TO-18.