SI2301DS vs AO3401A vs IRLML6402TRPBF - Which P-Channel SOT-23 MOSFET Should You Use?

Quick Summary

The AO3401A dominates: -30V rating (highest), 46mΩ R_DS(on) (lowest), -4.3A current (highest), ±12V gate tolerance, and 11 ns body diode recovery (fastest). It costs roughly the same as the SI2301DS at volume but delivers roughly 2x the current with half the on-resistance. The IRLML6402TRPBF is a solid part marred by NRND classification. The SI2301DS is electrically the weakest of the three - its one advantage is the tightest V_gs(th) spread (-0.45V to -0.95V) for ultra-low-voltage gate drive.

Parameter Comparison

Key Takeaways from the Numbers

• AO3401A dominates the headline specs: Highest voltage (30V), highest current (4.3A), lowest R_DS(on) (55mΩ @ 4.5V), highest power dissipation (1.4W), and fastest body diode (11 ns). It is the clear winner for any design that does not require sub-1.5V gate drive.
• IRLML6402TRPBF is the NRND "wildcard": Infineon has marked it Not Recommended for New Designs. Despite that, it offers excellent 65mΩ R_DS(on) and logic-level gate drive. Only choose it for existing qualified designs or repair inventory.
• SI2301DS has the tightest V_gs(th) and lowest capacitances: At -0.45V to -0.95V, its threshold is both lowest and tightest. Ideal for ultra-low-voltage gate drive (1.2V–1.8V), but its 130mΩ R_DS(on) is roughly 2.4× the AO3401A's.
• V_gs max traps: SI2301DS is limited to ±8V. If your circuit has 12V near the gate, you will destroy it. AO3401A and IRLML6402 both tolerate ±12V.

R_DS(on) vs Gate Drive

On-resistance depends on gate drive voltage. Here is how the three compare:

Real-world impact: At 2A load, the AO3401A dissipates 4 × 0.055 = 220 mW. The SI2301DS dissipates 4 × 0.130 = 520 mW - more than double the heat in the same tiny SOT-23 package. The SI2301DS would run 30°C hotter for the same current.

Gate Drive Compatibility

• 1.2V-1.8V gate drive: SI2301DS is the safest choice. IRLML6402 works at 1.8V with 0.6V margin. AO3401A is marginal at 1.8V - check your MCU's V_oh.
• 3.3V gate drive: All three work well. AO3401A has the highest overdrive at 2.0V above threshold.
• 5V gate drive: All three work, but SI2301DS needs caution - 5V is within its ±8V limit but leaves only 3V headroom for transients.

When to Choose Each MOSFET

Choose AO3401A when:

• You are starting a new design (best all-around specs, best availability)
• Your rail voltage is 12V or higher (30V rating gives headroom)
• Efficiency matters - lowest R_DS(on) at all drive voltages
• You want massive stock availability (high-volume production)
• Your circuit uses 3.3V or 5V gate drive

Choose IRLML6402TRPBF when:

• You are replacing a failed part in an existing production design
• You need Infineon's HEXFET ruggedness for harsh environments
• Your gate drive is 1.8V and you want guaranteed logic-level operation
• You understand the NRND status and have qualified a second source

Choose SI2301DS when:

• Your gate drive voltage is below 1.5V (tightest V_gs(th) of the three)
• Vishay is a preferred vendor on your AVL
• Legacy product maintenance - replacing SI2301DS with the same type
• You need the lowest gate charge for ultra-low switching loss

Replacement Compatibility

All three use the standard SOT-23 P-Channel pinout: Pin 1 = Gate, Pin 2 = Source, Pin 3 = Drain. Swapping between them requires no PCB change. The AO3401A is the optimum replacement target for both of the other two parts.

Frequently Asked Questions

Q1: Which P-Channel SOT-23 MOSFET has the lowest on-resistance?

A: The AO3401A, with 46mΩ typical at V_gs = -4.5V. The IRLML6402TRPBF is second at 52mΩ. The SI2301DS is 105mΩ typical - roughly 2.4× the AO3401A.

Q2: Can I replace SI2301DS with AO3401A on the same PCB?

A: Yes, both are SOT-23 with identical pinout. The AO3401A is a drop-in upgrade. However, check V_gs(th): the AO3401A max is 1.3V vs SI2301DS 0.95V. If your gate drive is below 1.5V, the SI2301DS may be safer.

Q3: Which MOSFET is best for 1.8V gate drive?

A: SI2301DS (0.95V max) is safest. IRLML6402TRPBF (1.2V max) works with 0.6V margin. AO3401A (1.3V max) has only 0.5V margin - check your MCU's V_oh carefully.

Q4: Why is the SI2301DS V_gs max only ±8V?

A: Vishay designed it with a thinner gate oxide for ultra-low threshold voltage. The trade-off is lower gate breakdown. Always limit gate drive to 5V or less. Use a zener clamp if your circuit has higher voltages nearby.

Q5: Can I use any of these for a 12V load switch?

A: Only the AO3401A (30V rating) has adequate margin. The other two are rated at 20V - technically 12V is within spec but you have no headroom for transients. For 12V designs, use the AO3401A.

Q6: Which has the best body diode recovery?

A: The AO3401A with 11 ns t_rr, roughly 2-3x faster than the SI2301DS (~30 ns) and IRLML6402TRPBF (~25 ns).

Q7: What is the price difference?

A: At reel quantities: AO3401A ~$0.03 (AOS original), SI2301DS ~$0.035-0.08 (clone vs Vishay original), IRLML6402TRPBF ~$0.10 (Infineon). The AO3401A has the best specs and the lowest price.

Q8: Is IRLML6402TRPBF still available despite being NRND?

A: Yes, still available while inventory lasts. Infineon has not announced final obsolescence. For new designs, we recommend the AO3401A.

Q9: Can I parallel these MOSFETs for higher current?

A: Yes, all three have positive R_DS(on) temperature coefficient, promoting current sharing. Use identical part numbers when paralleling, and individual gate resistors (~10Ω) to prevent oscillation.

Q10: Which is best for battery protection circuits?

A: All three work. The IRLML6402TRPBF and SI2301DS have the lowest V_gs(th), matching well with battery protection ICs that drive the gate at cell voltage (3.0-4.2V). The AO3401A also works but its 1.3V max threshold is still well below 3.0V.

Pricing & Availability

Our recommendation: If you are reading this comparison to choose a P-Channel SOT-23 MOSFET, buy the AO3401A. It costs less, outperforms the alternatives in every metric, and is stocked in quantities of millions. Contact ICMASS for current pricing and volume availability on all three parts.