Compare power MOSFETs at the gate voltage, current and temperature of the intended circuit. Brand reputation and a large drain-current rating cannot establish suitability. Infineon IRLZ44N and ST STP55NF06L are examples where similar device type and package still require a detailed engineering comparison.
Establish voltage margin and gate conditions
The Infineon IRLZ44N data sheet identifies a 55 V N-channel MOSFET. ST describes the STP55NF06L as a 60 V N-channel MOSFET in TO-220. That difference is relevant, but neither voltage rating alone establishes margin against an inductive load's switching overshoot.
Measure or conservatively bound the highest drain voltage, including wiring and load transients. Check the protection network and the repetitive operating conditions. Then compare on-resistance at a gate voltage actually delivered by the driver. Gate-threshold voltage indicates the start of conduction at a small test current; it is not a full-load drive recommendation.
Compare conduction and switching losses together
Use on-resistance at the relevant junction temperature to estimate conduction loss. For PWM operation, also evaluate gate charge, switching transitions and the driver's source and sink capability. A device with lower resistance may demand more drive current or incur different switching losses in the same circuit.
Review body-diode behavior when current can reverse or commutate. Keep the application specific: a slowly switched heater, a motor bridge and a high-frequency converter stress the device differently. A candidate that works well in one cannot be approved for the others by analogy.
Check the thermal path and operating area
Determine how heat moves from the junction through the package into the heatsink or board. Include mounting hardware, interface material, ambient temperature and enclosure airflow. The headline current rating does not describe a freely mounted device in every environment.
Use the safe operating area for startup, short pulses and any linear operation. Confirm package dimensions, lead order and tab connection before changing a BOM. Validate the replacement at minimum and maximum input, representative loads and hot ambient conditions, then document the approved driver and protection components.
Frequently asked questions
Does logic-level mean direct 3.3 V drive is always suitable?
No. Use the specified on-resistance conditions and verify the driver's available voltage during switching. Do not infer a guaranteed low-resistance operating point from the threshold specification or a category label.
Can a higher-current MOSFET replace a lower-current one automatically?
No. Voltage margin, gate charge, switching behavior, safe operating area and thermal resistance can change the result. Approve the complete circuit under its intended operating conditions.
Send SENICO an RFQ with the exact MOSFET order code, quantity, package and required date. Stock, price and lead time require quotation confirmation, and any alternative needs engineering approval.