TO-78 Package
Transistor Can Package TO-78 Case style, Metal Can
TO-78 Metal Can
The TO-78 package is a 8 pin device in a metal can. Note that a 6-pin package is shown, with two pins omitted. Pin locations 4 and 8 do not have a terminal attached.
Example configurations include a Dual Transistor package, [with both a NPN & PNP transistors] shown below and an Opto-coupler shown to the left.
Of course many other semiconductor configurations are possible than the ones shown here. The devices listed here are just meant to be possible examples.
Editor note; this package will hold any number of pins as long as they reside on the .200 inch pin circle, as shown in the diagram. This particular example has 6 pins, with terminals 4 and 8 missing, although they could be present on another package variant. Some designers may not use this package in there designs because the package is a through-hole part, although many companies still use through-hole components. Mixing through-hole components with surface mount parts adds to the complexity and cost of board manufacturing, so once some parts move to surface mount parts, all the parts used begin to be surface mount components.
