TO-220AB is the JEDEC designation for the three-straight-lead TO-220 package. The AB suffix names a lead count against a dimensional spec — not a larger tab and not a different bend. Three major vendors publish three different tolerance sets under that one name, and their mounting-hole bands do not fully overlap. Below: the dimensions side by side, the eleven pin styles the outline permits, and what the isolated version costs in thermal resistance.
Key takeaways
- AB means three straight leads to a dimensional spec. TO-220-3 is the generic catalog name for the same part.
- Mounting-hole bands run 3.54–3.73 mm (Vishay Semiconductors), 3.54–3.94 mm (Vishay Siliconix) and 3.75–3.85 mm (ST). They do not fully overlap.
- Lead pitch is effectively identical across all three, so the PCB footprint survives. The mechanical envelope does not.
- onsemi’s CASE 221AB defines eleven pin styles. The tab is pin 2 in every one, but pin 2 can be collector, emitter, anode, cathode, drain, source or main terminal 2.
- ITO-220AB withstands 1500 VAC terminal-to-heatsink and costs 3.5 °C/W junction-to-case against 2.0 °C/W for TO-220AB on the same die.
What TO-220AB actually designates
TO-220AB is the JEDEC outline designation for a TO-220 body carrying three straight leads on 2.54 mm nominal pitch, with one mounting hole through the tab. The AB suffix identifies lead count and lead form against a dimensional specification. TO-220AC is the two-lead member of the same family.
DigiKey’s TechForum draws the practical line: AB is the JEDEC call-out for three straight legs to a specific dimensional spec, while TO-220-3 is the generic catalog name for a TO-220 body with three legs. Distributors carry both fields on the same product page, which is where most of the confusion starts.
Treat secondary explanations carefully. At least one page currently ranking for this term describes the TO-220AB package as having an extended metal tab and TO-220AC as having a different lead bend. Both descriptions are wrong. The AB/AC split is lead count — three against two — on the same body.
[IMAGE 1: Front, side and rear views of a TO-220AB device with lead pitch, body envelope and tab hole dimensioned | alt: “TO-220AB package dimensions showing three straight leads on 2.54 mm pitch and the tab mounting hole”]
TO-220AB dimensions: three drawings, three answers
| Symbol and feature | Vishay Semiconductors, 95222 | Vishay Siliconix, 71195 | ST TO-220 type A |
| A — body thickness | 4.25–4.65 mm | 4.25–4.65 mm | 4.40–4.60 mm |
| D — body height | 14.85–15.25 mm | 14.85–15.49 mm | 15.25–15.75 mm |
| E — body width | 10.11–10.51 mm | 10.04–10.51 mm | 10.00–10.40 mm |
| e — lead pitch | 2.41–2.67 mm | 2.41–2.67 mm | 2.40–2.70 mm |
| e1 — lead 1 to lead 3 | 4.88–5.28 mm | 4.88–5.28 mm | 4.95–5.15 mm |
| ØP — mounting hole | 3.54–3.73 mm | 3.54–3.94 mm | 3.75–3.85 mm |
| L — lead length | 13.52–14.02 mm | 13.35–14.02 mm | 13.00–14.00 mm |
| L1 | 3.32–3.82 mm | 3.32–3.82 mm | 3.50–3.93 mm |
| Q | 2.60–3.00 mm | 2.60–3.00 mm | 2.65–2.95 mm |
| H1 | 5.84–6.86 mm | 6.09–6.48 mm | 6.20–6.60 mm |
Vishay Semiconductors doc 95222 is dated 23 February 2024 and states conformance to the JEDEC TO-220AB outline. Vishay Siliconix doc 71195 is Rev P, 16 June 2014, drawing 5471. The ST column is the TO-220 type A mechanical data published in the STP16NF06 datasheet, CD00002501 Rev 8.
The pitch is the good news. All three specify effectively the same lead spacing, so a single PCB footprint accepts any of them.
The tab hole is the bad news. Vishay Semiconductors caps ØP at 3.73 mm; ST starts at 3.75 mm. Those two bands do not overlap at all. And the two Vishay divisions disagree with each other by 0.21 mm at the top of the range — same company, same TO-220AB package name, two drawings.
Body height splits the same way. The 95222 band tops out at 15.25 mm exactly where ST’s begins.
Worked example: sizing tab hardware across vendors
Take the full span across the three drawings: ØP can be as small as 3.54 mm and as large as 3.94 mm.
- A shoulder bushing sized for ST’s parts — say 3.65 mm outside diameter, comfortable in a 3.75–3.85 mm hole — meets 0.11 mm of interference in a Vishay part at 3.54 mm. It will not enter.
- A 3.40 mm bushing clears every drawing. In the largest hole it leaves 0.54 mm of diametral clearance, which is 0.27 mm of radial float per device.
That float is not free. On a heatsink drilled at fixed pitch for a row of devices, 0.27 mm of radial play adds directly to the lead-position error your PCB holes must absorb.
The rule: size the bushing to the smallest ØP you might receive, then check the resulting float against your board’s hole tolerance rather than assuming it disappears.
The tab is pin 2, but pin 2 is not always the collector
onsemi’s CASE 221AB drawing (Issue A, 16 November 2010, document 98AON23085D) lists eleven pin styles for one outline. The tab is designated pin 4 and is electrically common with pin 2 in every style. What pin 2 is changes completely.
| Style | Pin 1 | Pin 2 | Pin 3 | Tab (pin 4) |
| 1 | Base | Collector | Emitter | Collector |
| 2 | Base | Emitter | Collector | Emitter |
| 3 | Cathode | Anode | Gate | Anode |
| 4 | Main terminal 1 | Main terminal 2 | Gate | Main terminal 2 |
| 5 | Gate | Drain | Source | Drain |
| 6 | Anode | Cathode | Anode | Cathode |
| 9 | Gate | Collector | Emitter | Collector |
| 11 | Drain | Source | Gate | Source |
Two rows deserve attention. Style 5 is the familiar MOSFET order, gate–drain–source, with the tab at drain. Style 11 reverses it entirely — drain–source–gate, with the tab at source. A board laid out from habit against a Style 11 part shorts the gate drive to the heatsink.
Style 2 is the other trap: a bipolar transistor with the tab at the emitter rather than the collector. The “tab is the collector” rule that most engineers carry is a Style 1 rule, not a package rule.
[IMAGE 2: Two TO-220AB outlines side by side annotated with Style 5 and Style 11 pin assignments, showing the tab at drain versus source | alt: “TO-220AB pin styles comparing gate-drain-source and drain-source-gate assignments on the same outline”]
ITO-220AB: the isolated sibling that keeps the AB suffix
Vishay’s MBR20xxxCT family (document 89033, revision 11 June 2018) puts one Schottky die into three packages that all carry an AB-family name.
| Parameter | TO-220AB, MBR20100CT | ITO-220AB, MBRF20100CT | TO-263AB, MBRB20100CT |
| Typical RθJC per diode | 2.0 °C/W | 3.5 °C/W | 2.0 °C/W |
| Typical RθJA per diode | 60 °C/W | — | 60 °C/W |
| Unit weight | 1.88 g | 1.75 g | 1.38 g |
| Isolation, terminal to heatsink, 1 min | — | 1500 VAC | — |
| Delivery | 50 per tube | 50 per tube | 50 per tube, or 800 per reel |
| Solder / moisture spec | Solder bath 275 °C, 10 s | Solder bath 275 °C, 10 s | MSL 1, 245 °C peak |
Encapsulating the tab costs 75% more junction-to-case resistance and buys 1500 VAC of isolation with no washer, no bushing and no assembly step. The weight difference — 1.88 g against 1.75 g — is the copper that came out.
TO-263AB is the surface-mount member and keeps the same AB suffix. TO-262AA, the cut-tab through-hole version Vishay lists alongside these in other datasheets, does not. The suffix is not a reliable guide to mounting style.
What the AB suffix does not tell you
The name is a mechanical outline. Everything below comes from the device datasheet, not the package designation.
Handling. Doc 89033 specifies the through-hole TO-220AB and ITO-220AB by solder bath, 275 °C maximum for 10 s per JESD 22-B106. Only the surface-mount TO-263AB carries an MSL rating — level 1 per J-STD-020 at a 245 °C peak. A through-hole TO-220AB has no floor life to manage.
Compliance. The same datasheet specifies matte tin leads solderable per J-STD-002 and JESD 22-B102, a UL 94 V-0 molding compound, and an E3 suffix meeting the JESD 201 class 1A whisker test. Mounting torque is capped at 10 in·lb maximum.
Old stock. onsemi’s CASE 221AB drawing carries a note that product shipped before 2008 had dimension S at 1.143–1.397 mm against the current 0.508–0.61 mm. If you are working through new-old-stock or a long-life spares pool, one controlled dimension on the current drawing does not describe the parts in the bin.
[IMAGE 3: Cutaway comparison of TO-220AB and ITO-220AB tabs showing exposed metal against fully encapsulated flange | alt: “TO-220AB versus ITO-220AB tab construction showing exposed and encapsulated mounting flange”]
Five mistakes that reach the assembly line
- Treating TO-220AB and TO-220-3 as different parts. They are the same package under a JEDEC name and a catalog name.
- Sizing the shoulder bushing to a nominal hole. Design to 3.54 mm worst case, not to 3.8 mm.
- Assuming the tab is the collector or the drain. Eleven pin styles share this outline; check the style, not the family.
- Copying a footprint’s pin order between MOSFET parts. Style 5 and Style 11 are mirror images on the same body.
- Specifying an MSL bake for a through-hole TO-220AB package. The through-hole versions are qualified by solder bath, not by floor life.
Frequently asked questions
What is the difference between TO-220AB and TO-220-3?
None mechanically. TO-220AB is the JEDEC designation for three straight leads meeting a specific dimensional spec; TO-220-3 is the generic catalog name for a TO-220 body with three legs. Distributors list both fields on one product page. Search on the generic name, verify conformance against the JEDEC name.
Is TO-220AB the same as TO-220?
TO-220 is the family; TO-220AB is the three-lead member of it. The family also includes the two-lead TO-220AC, the fully encapsulated TO-220F and TO-220FP, and five- and seven-lead versions. When a datasheet says only “TO-220”, check the lead count before assuming AB.
What is ITO-220AB?
The isolated TO-220AB: the same outline with the mounting flange encapsulated in the molding compound. On Vishay’s MBR20xxxCT family it withstands 1500 VAC terminal-to-heatsink for one minute and raises typical junction-to-case resistance from 2.0 to 3.5 °C/W on the same die.
Is the TO-220AB tab always the collector?
No. The tab is electrically common with pin 2 in all eleven pin styles on onsemi’s CASE 221AB drawing, but pin 2 is the collector only in Styles 1 and 9. It is the emitter in Style 2, the anode in Style 3, the drain in Style 5, the cathode in Style 6 and the source in Style 11.
What is the TO-220AB mounting hole size?
It depends on whose drawing you read. Vishay Semiconductors specifies 3.54 to 3.73 mm, Vishay Siliconix 3.54 to 3.94 mm, and ST 3.75 to 3.85 mm for its TO-220 type A. The bands do not fully overlap, so size hardware to 3.54 mm worst case.
What to do next
Before ordering hardware: pull the outline drawing for the specific manufacturer you are buying, not a generic TO-220AB package reference, and size the bushing to the smallest ØP in your approved-vendor list.
Before laying out the board: read the pin style, not the package name. On a MOSFET, confirm whether gate is pin 1 or pin 3 before the footprint leaves your hands.
Before choosing between TO-220AB and ITO-220AB: run the thermal budget at 3.5 °C/W rather than 2.0 °C/W. If the derated number still clears, the isolated part deletes the washer, the bushing and the step that most often shorts a tab to chassis.
Before qualifying old stock: check the drawing revision date against the parts you hold. A dimension that changed in 2008 is still documented, and it is still different.
