STF40NF20 Equivalent & Substitute Parts

Part Overview

The STF40NF20 is an N-Channel MOSFET manufactured by STMicroelectronics, rated for 200V drain-to-source voltage with 40A continuous drain current at 25°C. This device is housed in a TO-220FP through-hole package and is part of the STripFET™ series. The part maintains Active product status with 1330 units in current inventory.

Substitute parts become necessary when the primary part reaches end-of-life status, experiences supply constraints, or when design requirements permit operation within the electrical and mechanical parameters of alternative devices. The FQPF32N20C from onsemi represents a functionally related alternative, though with reduced current rating and different electrical characteristics that must be evaluated against application requirements.

Substiute Parts

STF40NF20

STMicroelectronicsIn Stock: 1350STF40NF20 Datasheet

Current PartRFQ

FQPF32N20C

onsemiIn Stock: 22219FQPF32N20C Datasheet

SimilarRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution eligibility for the STF40NF20 is determined by the following critical parameters:

Voltage Rating Compatibility: The substitute part must maintain a Drain to Source Voltage (Vdss) rating equal to or greater than 200V to ensure safe operation in the same circuit topology.

Current Capacity: The substitute part must support continuous drain current (Id) at 25°C sufficient for the application. The STF40NF20 operates at 40A; substitute parts with lower current ratings require circuit-level verification that peak and continuous current demands do not exceed the substitute device's specifications.

On-State Resistance (Rds On): Lower Rds On values indicate superior conduction efficiency and reduced power dissipation. Substitute parts with higher Rds On values generate additional heat and may require thermal management adjustments.

Gate Charge (Qg): Gate charge affects switching speed and driver circuit requirements. Substitute parts with higher gate charge values demand greater driver current capacity.

Package and Mounting: The STF40NF20 uses TO-220FP through-hole packaging. Substitute parts must use compatible through-hole packages (TO-220F or TO-220FP) to maintain PCB layout compatibility.

Thermal and Compliance Ratings: Operating temperature range, RoHS compliance, and REACH status must align with application and regulatory requirements.

The FQPF32N20C meets voltage rating requirements (200V Vdss) and package compatibility (TO-220F-3 through-hole) but operates at reduced continuous current (28A versus 40A) and exhibits higher on-state resistance (82 mOhm versus 45 mOhm).

Parameter Comparison

Engineering Selection Recommendations

Primary Part (STF40NF20): The STF40NF20 maintains Active product status with established supply availability (1330 units in stock). This device is the preferred selection for new designs and ongoing production. RoHS3 compliance and REACH unaffected status satisfy current regulatory requirements. The 40A continuous current rating and 45 mOhm on-state resistance provide optimal performance for applications requiring maximum current capacity and minimal conduction losses.

Substitute Part (FQPF32N20C): The FQPF32N20C carries Obsolete product status, indicating discontinued manufacturing and declining availability. This part is suitable only for legacy system maintenance or repair applications where the original part specification cannot be met. The reduced current rating (28A versus 40A) and elevated on-state resistance (82 mOhm versus 45 mOhm) result in higher power dissipation and thermal stress. Applications operating at or near the STF40NF20's 40A rating cannot use this substitute without circuit redesign. The higher gate charge (110 nC versus 75 nC) increases driver circuit demands. RoHS3 compliance and REACH unaffected status are maintained.

Compliance Considerations: Both parts satisfy RoHS3 and REACH requirements. Operating temperature ranges are identical (-55°C to 150°C). Package compatibility is confirmed for through-hole PCB assembly.

Frequently Asked Questions (FAQ)

Q: Can the FQPF32N20C directly replace the STF40NF20 in existing designs?

A: Direct replacement is not recommended for applications operating above 28A continuous drain current. The FQPF32N20C's reduced current rating and higher on-state resistance create thermal and performance limitations. Circuit-level analysis is required to confirm that actual operating currents remain within the substitute part's specifications.

Q: What are the thermal implications of using the FQPF32N20C as a substitute?

A: The FQPF32N20C exhibits higher on-state resistance (82 mOhm versus 45 mOhm), resulting in increased power dissipation at equivalent current levels. The substitute part's 50W maximum power dissipation rating exceeds the STF40NF20's 40W rating, but actual thermal performance depends on circuit current, duty cycle, and heatsink design. Applications with marginal thermal margins may experience elevated junction temperatures.

Q: Are the gate drive requirements different between these parts?

A: Yes. The FQPF32N20C requires higher gate charge (110 nC versus 75 nC), demanding greater driver current capacity. Gate drivers must supply sufficient current to charge the gate within acceptable switching time windows. Existing driver circuits designed for the STF40NF20 may require adjustment or replacement.

Q: Why is the FQPF32N20C listed as Obsolete?

A: Obsolete status indicates the manufacturer has discontinued production. Remaining inventory is limited and subject to depletion. This part should not be selected for new designs. Use only for repair or maintenance of legacy systems where the original part is unavailable.

Q: Are package dimensions identical between TO-220FP and TO-220F-3?

A: Both packages use the TO-220-3 Full Pack configuration with identical lead spacing and through-hole mounting compatibility. PCB footprints are interchangeable. Mechanical fit on standard TO-220 heatsinks is confirmed for both parts.

Q: What is the significance of the different Vgs (Max) ratings?

A: The STF40NF20 specifies ±20V maximum gate-source voltage, while the FQPF32N20C permits ±30V. This difference reflects different gate oxide designs. Applications must not exceed the selected part's Vgs (Max) rating to prevent gate oxide breakdown. Existing gate drive circuits designed for ±20V operation are safe for the FQPF32N20C but do not require the higher voltage capability.

Q: Can both parts operate across the full -55°C to 150°C temperature range?

A: Yes. Both the STF40NF20 and FQPF32N20C specify identical operating temperature ranges (-55°C to 150°C junction temperature). Thermal performance and on-state resistance characteristics vary with temperature according to each manufacturer's datasheet specifications.