How to Quickly Identify MOSFET Parameters from Markings

1. Two Main Naming Conventions

Convention1: Direct Marking (Most common for SMD & low-voltage MOSFETs,format: XXNYY / XXPYY)

Format: Current + Channel (N/P) + Drain-Source Voltage Rating

• Letter N = N-channel (mainstream type); P = P-channel
• Leading digits: Maximum continuous drain current \(I_D\) (Unit: A)
• Trailing digits: Drain-source voltage rating \(V_{DS}\) (Unit: V)

Examples

• 30N06: 30A, N-channel, 60V
• 20P10: 20A, P-channel, 100V
• 80N08: 80A, N-channel, 80V

Convention2: IR Series (Through-hole high-power MOSFETs)Format: IRF + Digits + Suffix

• IRF: Brand prefix, ignore it.
• The middle two digits × 10 = Voltage rating (Unit: V)
• Suffix N = N-channel; P = P-channel
• Drain current shall be checked in datasheets; current rating is fixed for models with identical core digits.

Examples

• IRF540N: 40×10 = 400V, N-channel, rated current 33A
• IRF320: 20×10 = 200V, N-channel
• IRF9540: P-channel, 40×10 = 400V

Convention 3: High-voltage MOSFETs (Infineon IPW/IPP series for industrial & power supplies)Format: IPWxxRxxx

• First two digits × 10 = Voltage rating (Unit: V)
• Digits after R: On-resistance \(R_{DS(on)}\) (Unit: mΩ)

Examples

• IPW60R041: 600V, \(R_{DS(on)}=4.1\mathrm{m}\Omega\)
• IPP45R190: 450V, \(R_{DS(on)}=190\mathrm{m}\Omega\)

Convention 4: Mini SMD MOSFETs (SOT-23 package, small-signal devices)

• Markings are usually 3~4 digit codes with no intuitive current/voltage indication. Refer to common models directly:
• AO3400: N-channel, 30V, 5.8A
• SI2302: N-channel, 20V, 2.8A
• SI2301: P-channel, 20V, 2.3A

No universal calculation rule for these codes; memorize mainstream models for daily use

2. Meanings of Extra Digits & Characters on Markings

1. 4-digit number (Batch & production date): First two digits = Year; last two digits = Production week
2. Example: 2612 = 12th week of 2026
3. Suffixes like TL, MS, CFD: Indicate package, process or version, no impact on core electrical parameters
4. Small logos: Manufacturer marks, can be ignored.

3. 3-Step Quick Identification Procedure

1. Check letters: Locate N/P to confirm channel type.
2. Decode digits: Calculate voltage rating, current and on-resistance per corresponding rules.
3. Classify package & type:

• Through-hole high-power devices: Follow IR series rules
• High-current SMD devices: Follow XXNYY / XXPYY rules
• Tiny SOT-23 packages: Check common model list
• 

4. Quick Reference for Frequently Used Models

5. Supplementary Notes

1. Only nominal absolute maximum ratings can be obtained by visual decoding. Parameters such as junction temperature, gate drive voltage and switching speed must be verified in official datasheets.
2. MOSFETs with the same digital marking from different manufacturers share basically identical current and voltage ratings; differences mainly lie in on-resistance and package.
3. For SMD MOSFETs with pure code markings (without N/P or regular digit combinations), look up the full model and datasheet for accurate parameters.
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