How to Read Infineon (IR) MOSFET · IGBT Part Numbers — 4-digit numbers in IRF3205 · IRF4905, the N in IRFZ44N, BSC014N03LS · IKW40N120H3

Illustration: A customer holds two black TO-220 parts (IRF3205 · IRF4905) and asks, “They're both IRF, so they're the same, right?” A female staff member in a red apron answers, “Look at the middle digits. 32 is N-channel, 49 is P-channel!”

IRF3205 · IRF4905 · IRFZ44N · IRF540N are the power MOSFET part numbers you see most often in Guro. They were originally International Rectifier (IR) part numbers, but today Infineon makes and sells them under the same part numbers. Infineon also uses its own part numbering systems, such as OptiMOS (BSC · IPP …) and IGBT (IKW …).

The FET part number guide (post 56) covered only IR's old 3-digit rule (IRF540 · IRFZ44). This post covers the 4-digit numbers that came later (IRF3205 · IRF4905), the suffixes (N · S · L · PbF), and Infineon's newer MOSFET and IGBT part numbers.

Values are from IR's Part Numbering System, Infineon's MOSFET selection guide (2024-09) · IGBT datasheet explanation (2015-09), and Infineon datasheets and product pages (checked 2026-10-30). Text in English quotation marks is the original wording. Click a part number to go to eGuro Part Search.

1. IR part numbers = now Infineon products

Part numbers like IRF3205 · IRF4905 · IRFZ44N are now listed on Infineon's website as Infineon products, and their datasheets carry the Infineon name. Infineon datasheets still keep the IR-era phrase “Advanced HEXFET Power MOSFETs”. So even if the manufacturer column of a quote shows a mix of IR, International Rectifier, Infineon and IFX, the same part number means the same line.

2. Starting with IRF doesn't mean only Infineon — Vishay IRF part numbers

All are TO-220. Values are from Vishay's MOSFET list and Infineon product pages (checked 2026-10-30). Since the voltage and current differ, the parts with and without N are not the same component. IRF520N · IRF530N · IRF630N · IRFP250N are also Infineon-only, while IRF520 · IRF530 · IRF630 · IRFP250 without N are Vishay products.

There are exceptions. IRFP22N50A (500V · 22A · TO-247), with an N in the middle, exists at both companies — it is in Vishay's MOSFET list, and on Infineon's website it is marked discontinued. So “does it end in N?” is only a hint; always check the manufacturer column of the stock list too.

The part numbers above have no product page on Infineon's website (checked 2026-10-30: /part/IRF540 · IRF630 · IRF740 · IRF840 · IRFBC40 all missing). Vishay datasheets can be downloaded at https://www.vishay.com/doc?document-number (e.g. IRF740 = doc?91054).

Vishay sells the same chip under two names. The ordering table in the IRF540S datasheet (document 91022) lists the lead-free version IRF540SPbF and the lead-free + halogen-free version SiHF540S-GE3 together in one table. If a quote shows SiHF540S, it is still the IRF540S line. Parts with A · LC at the end, like IRF740A · IRF740LC, are different versions with their own datasheets, and the meaning of the letters is not in any official document.

3. Old 3-digit part numbers IRF540 · IRFZ44 (Conventional HEXFET)

The IR document says this rule applies to “commercial, discrete Generation 3 HEXFET Power MOSFETS”. The detailed explanation is in the FET part number guide (post 56); here we only revisit the voltage letters.

So IRF540N is TO-220 · N-channel · 5 = 100V, and IRFZ44N is Z = 60V class. (The actual IRFZ44N datasheet value is 55V.) A 9 means P-channel — IRF9540N = P-channel 100V.

4. Reading 4-digit part numbers IRF3205 · IRF4905 (Advanced HEXFET)

The IR document says this rule applies to “commercial, discrete Generation 4 OR 5 HEXFET Power MOSFETS”. The first two digits are a “random n-channel die #” · “random p-channel die #”, so the number itself has no meaning, but 01–48 means N-channel and 49–69 means P-channel. The last two digits are the voltage: “01 = 10-19V”, “10 = 100V”.

Numbers starting with 70–79 are product numbers for small packages such as SO-8 (“IRF71-74xx= SO8”, “IRF75-76xx= Micro 8”). These carry no voltage or package indication and mix N · P · N+P, so you cannot tell from the number — IRF7313 is dual N-channel, IRF7404 is P-channel.

5. Part numbers that fit the rule · that don't

We checked the actual polarity and voltage on Infineon product pages against the 4-digit rule one by one.

The B after IRF, as in IRFB4110, means “TO-220 (600-1000V)” in the IR table, yet IRFB4110 is 100V. In later part numbers, even the package letter may not match the old table.

6. Suffixes N · S · L · TR · PbF

IRF3205 and IRF3205Z are both 55V · 110A · TO-220, but on Infineon's website IRF3205 is active while IRF3205Z is marked not for new design · discontinued. Even a one-letter difference is treated as a different product.

7. New MOSFETs BSC014N03LS · IPP060N06N (OptiMOS)

The gate letters are “N = Normal level (NL) 10.0”, “L = Logic level (ELL) 4.5”, K = 2.5V, J = 1.8V. The table above was read using the selection guide's rules, so check the actual figures in the datasheet.

2015–2019 StrongIRFET parts (e.g. IRF135SA204) are IR + gate letter + voltage (135V) + package (SA) + sequential number. New part numbers since 2019 changed to the order I + 2-letter package (PP = TO-220, SC = SuperSO8 …) + gate letter + brand (M = OptiMOS, F = StrongIRFET) + resistance + voltage.

8. IGBT IKW40N120H3

The guide's example IKW75N65ES5 is K (IGBT + diode) · W (TO-247) · 75 (75A at 100℃) · N · 65 (650V) · E (diode type) · S5 (soft-switching Trenchstop 5).

9. Table of common IRF part numbers (Infineon product pages)

IR part numbers often seen in Guro, summarized with values from Infineon product pages (checked 2026-10-30). Current is based on a 25℃ case temperature.

Not for new design means you can still buy it but should not use it in new products; discontinued means production has ended. Domestic distributors often still have stock of discontinued part numbers, so look them up with eGuro Part Search.

10. Pitfalls when ordering

Illustration: A customer in a jumper shows IRF540 and IRF540N parts on his palm and asks, “It's just one N of difference, so either one works, right?” A female staff member in a red apron holds up two datasheets, IRF540 · IRF540N, and answers, “They're made by different companies. Compare the datasheets!”

• IRF ≠ Infineon only — IRF540 · IRF740 · IRF840 · IRFP460 without N at the end are Vishay products. Some, like IRFP22N50A, exist at both companies, so check the manufacturer column too
• 4-digit numbers — 01–48 N-channel · 49–69 P-channel, last 2 digits = voltage. But later part numbers (IRF1010E · IRFB4227 etc.) don't fit
• IRF3205 ↔ IRF4905 — Same 55V TO-220, but N-channel ↔ P-channel. Swapping them means the circuit won't work
• Part numbers with N — IRF540 and IRF540N are different generations. Compare the datasheet figures
• S · L — D2Pak · TO-262 versions of the same chip. Different board footprint
• E · Z — No official explanation. IRF3205 and IRF3205Z are different products (Z is marked discontinued)
• Discontinued · not for new design — IRLML2502 · IRLML6402 · IRF7404 · IRF3808 etc. are discontinued at Infineon

Sources: International Rectifier Part Numbering System (Conventional · Advanced HEXFET) · Infineon Selection guide MOSFET OptiMOS™ and StrongIRFET™ (2024-09, pp.41–43) · Infineon Explanation of discrete IGBTs' datasheets (2015-09, Table 1) · Infineon datasheets IRF1018E · IRF3205 · IRFZ44N · IRL3705N · IRF4905 · IRF540N · Infineon product pages (2026-10-30) · Vishay MOSFET list (vishay.com/en/mosfets, 2026-10-30) · Vishay datasheets 91021 IRF540 · 91022 IRF540S · 91264 IRFR024 · 91031 · 91054 · 91070 · 91212 · 91237 · 91291. Before actually ordering, check the manufacturer's datasheet for the part number.