TO-257 Package
Transistor Packages TO257 Case style, with Metal Tab
TO-257 3-Terminal Package
The TO-257 transistor is a through-hole device, with three leads and a tab. Although not shown the leads may also be bend upwards, but a bit less common. Another variant uses semi-flexible leads with the origins being rigid which is even less common.
TO-257 BJT Terminals: Lead 1, Base. Lead 2, Collector. Lead 3, Emitter
TO-257 FET Terminals: Lead 1, Drain. Lead 2, Source. Lead 3, Gate
Tab mount. A type of package which provides a method of readily attaching one surface of the
semiconductor device to a heat dissipater [heat-sink] to achieve thermal management of the case temperature. If required a metal washer and thermal grease could also be used.
Similar packages, 2-Terminal TO-257, and TO-254 [with different dimensions].
Devices that use the TO-257 package include;
2N6249T3 Transistor, and 2N6676T3 Transistor
TO-257 Transistor Types
NPN Power Transistors; 2N6306-T3, 2N6308-T3, 2N6249-T3, 2N6250-T3, 2N6251-T3
N-Channel Radiation Hardened Field Effect Transistor 2N7380, 2N7381 [TO-257AA]
P-Channel Radiation Hardened Field Effect Transistor 2N7382, 2N7383 [TO-257AA]
N-Channel Field Effect Transistor, Radiation Hardened (Total Dose and Single Event Effects), 2N7399, 2N7400, 2N7401, 2N7402, 2N7512, 2N7513, and 2N7514
P-Channel Field Effect Transistor, Radiation Hardened (Total Dose and Single Event Effects), 2N7440, and 2N7441
Diode, Silicon, Schottky, Power Rectifier, Common Cathode or Common Anode Center Tap 1N6785
TO-257AA Transistor Types
Common Cathode Gallium Arsenide Power Rectifier Diode 1N6753 [Anode (I) 1, Anode (II) 3. Cathode 2]
Gallium Arsenide Power Rectifier Diode 1N6757 [Anode 1, 3. Cathode 2]
Dual Common Cathode/Anode Center Tap Ultrafast Power Rectifier Diode, 1N6762 through 1N6765 [Anode (I) 1, Anode (II) 3. Cathode 2]
Diode, Silicon, Power Rectifier, Dual, Common Cathode or Anode Center Tap, Ultrafast, Types 1N6768 through 1N6771, 1N6772, 1N6773 [Anode (I) 1, Anode (II) 3. Cathode 2]
Field Effect Radiation Hardened (Total Dose and Single Event Effects) Transistors, N-Channel, 2N7465T3, 2N7466T3, 2N7482T3, 2N7483T3, and 2N7484T3
NPN Power Transistor 2N6676T3, 2N6678T3
Diode Array; 1N6664 through 1N6666 | 1N6664 |
Editor note some use the term Tab Mount, others use Flange-Mount.
The TO-257 is part of the TO-25x series of component packages.