STMicroelectronics STF40NF20

Overview

STF40NF20 from STMicroelectronics is an N-channel 200V Power MOSFET in TO-220FP package, rated for 40A continuous drain current at 25°C, with R_DS(on) ≤ 0.045Ω at V_GS = 10V and total gate charge Q_g = 75nC. It features low intrinsic capacitances, 100% avalanche tested operation, and is optimized as a primary switch in isolated DC-DC converters requiring high efficiency and robustness.

For engineers reviewing the STF40NF20 datasheet, STF40NF20 pinout, STF40NF20 application, or STF40NF20 equivalent, key selection criteria include its 40W power dissipation limit (TO-220FP), junction-to-case thermal resistance of 3.1°C/W, avalanche energy rating of 230mJ, and suitability for hard-switched SMPS topologies where diode recovery and gate drive loss minimization are critical.

Technical Context

This STripFET™ II device uses a planar vertical structure to achieve low R_DS(on) × Q_g figure of merit (FoM), enabling high-frequency switching with reduced conduction and switching losses. Its gate threshold voltage (2–4V) ensures reliable turn-on with standard 10V gate drivers while maintaining noise immunity.

The integrated body diode exhibits t_rr = 192ns and Q_rr = 922nC at 25°C (20A, 100A/µs), supporting ZVS-capable flyback and forward converters. Thermal design is constrained by R_th(j-case) = 3.1°C/W and P_tot = 40W at T_C = 25°C - significantly lower than TO-220/TO-247 variants due to the FP (Full-Pak) package's reduced copper slug area.

Key Specifications

Pinout & Package

STF40NF20 uses the TO-220FP (Full-Pak) package: insulated plastic case with electrically isolated tab, enabling direct mounting to heatsinks without insulating washers. The package has three leads - Gate (G), Drain (D), Source (S) - with lead 1 = Gate, lead 2 = Drain, lead 3 = Source, matching standard TO-220 pinout orientation but with enhanced creepage/clearance.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar N-channel 200V Power MOSFET applications.

Compared with STP40NF20, STF40NF20 trades 4× lower power dissipation for electrical isolation and compact footprint; versus IRF640NPbF, it delivers 4× lower on-resistance and guaranteed avalanche capability - making it preferable for space-constrained, high-reliability SMPS where thermal and ruggedness margins are tight.

Availability

STF40NF20 is available at Aetrix Electronics and suitable for AC-DC adapters, industrial DC-DC converters, LED drivers, and motor control modules requiring stable component supply and long-term manufacturability.

Supply support for STF40NF20 includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, designing and manufacturing microcontrollers, power devices, analog ICs, and MEMS sensors for industrial, automotive, and consumer markets.

The STripFET™ Power MOSFET product line targets high-efficiency power conversion systems, emphasizing low gate charge, rugged avalanche performance, and thermal robustness for SMPS, motor drives, and lighting applications.

FAQ

What is the maximum continuous drain current for STF40NF20 at 100°C case temperature?

The maximum continuous drain current (I_D) drops to 25A at T_C = 100°C, per Table 1 Absolute Maximum Ratings. This reflects thermal derating due to reduced channel conductivity and increased R_DS(on) at elevated temperatures - designers must ensure heatsink design maintains T_C ≤ 100°C for sustained 25A operation.

Does STF40NF20 require a gate resistor for safe operation?

Yes - a gate resistor (typically 10–47Ω) is required to dampen ringing caused by parasitic inductance and prevent spurious turn-on from dv/dt coupling. The device's low input capacitance (C_iss = 2500pF) and fast switching (t_r = 44ns) make it sensitive to layout-induced oscillation without proper gate control.

Can STF40NF20 replace STP40NF20 in an existing TO-220 footprint?

No - although both share identical pinout (G-D-S), STF40NF20 uses TO-220FP with insulated tab and different mounting hole spacing. Mechanical interference and thermal pad misalignment will occur if substituted without PCB revision; the FP variant also has 4× lower power rating, risking thermal failure.

Is STF40NF20 suitable for synchronous rectification in secondary-side applications?

No - STF40NF20 is optimized as a high-side primary switch, not a low-side synchronous rectifier. Its body diode reverse recovery characteristics (Q_rr = 922nC) are too slow for efficient secondary-side operation; dedicated low-Q_rr, logic-level MOSFETs like STP16NF06L are recommended instead.