page_title: TO-3
section_title: Common components that use the TO-3 package
hierarchical_section_title: TO-3 / Common components that use the TO-3 package
caption_attribution_description: Русский: Транзистор кт819гмEnglish: Transistor KT819GM; manufactured by Kremny Bryansk in April 2014
context_page_description: In electronics, TO-3 is a designation for a standardized metal semiconductor package used for power semiconductors, including transistors, silicon controlled rectifiers, and, integrated circuits. TO stands for "Transistor Outline" and relates to a series of technical drawings produced by JEDEC.
  The TO-3 case has a flat surface which can be attached to a heatsink, normally via a thermally conductive but electrically insulating washer. Its package usually have two leads, the case being the third connection, though devices with more leads are used. The TO-3 case has two mounting holes, with the centers spaced 1.186 inches apart. The design originated at Motorola around 1955. The lead spacing was originally intended to allow plugging the device into a then-common tube socket.
context_section_description: Common voltage regulators:
  LM317, voltage regulator
  LM78xx, voltage regulator
  LM340, voltage regulator
  Common transistors:
  2N3055, NPN power transistor
  2N2955, PNP power transistor
  KD503, NPN power transistor
caption: КТ819ГМ NPN power transistor (Soviet 2N3055 copy) in TO-3 package
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