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TO-92 (TO-226) Component Package

Geoffrey Hunter Author


TO-92 (Transistor Outline 92) is a very common family of through-hole component packages for low-power through-hole transistors, MOSFETs, and linear regulators.

TO-92 (TO-226AA)

If a package is just labelled as TO-92, then it is most likely to be the "standard" variant, which is also known as TO-226AA.

A 3D render of the TO-92-3 component package.


  • 29-11: On Semiconductor.
  • TO-226AA: JEDEC name for the standard TO-92 package.
  • TO-92: If any additional info is missing, it's likely to be the standard TO-92 package.
  • Z Package: Analog Devices.


Mounted height is typically 10mm (including body and enough space to get the through-hole legs mounted in the PCB).

Pitch is variable, depending on how you bend the legs. Commonly adjusted to 2.54mm.

Thermal Resistance

  • 220C/W220^{\circ}{\rm C}/W (package only)
  • 175C/W175^{\circ}{\rm C}/W (plated through-holes)
  • 145C/W145^{\circ}{\rm C}/W (plated through-holes and 0.25inch20.25inch^2 pad per lead)

TO-92/18 (TO-226AB)

The TO-92/18 variant of the TO-92 package is similar to the standard package (which is just called the TO-92), except that it has a longer body. It is also known as the TO-226AB or TO-92MOD package.

A 3D render of the TO-92/18 (TO-226AB) component package.

Pin Numbering

Pin numbering is always done from left-to-right, when the flat side of the TO-92 package is facing you and the legs are pointing downwards, as shown in the following diagram:

A 3D render of the TO-92 component package with pin numbering.

This is applicable to both the standard TO-92 (TO-226AA) and TO-92/18 (TO-226AB) variants.

Standard Pinouts

The pinout for JEDEC-named 2N series transistors is standardised as per the following table:

Pin NumberBJT Connection
1Emitter (E)
2Base (B)
3Collector (C)


There are a limited range of heatsinks available for the TO-92 component package. Aavid Thermalloy makes two TO-92 heatsinks, one of which is currently available (as of May 2016) on DigiKey.

The TO-92 clip-on heatsink by Aavid Thermalloy (part num. 575200B00000G).

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