IRF840 Pinout, Equivalent, Application, Datasheet

Before diving into the detailed sections, note the IRF840 pinout, it uses the standard TO-220 layout: Gate–Drain–Source (G-D-S). Understanding this pin mapping beforehand helps ensure correct installation in high-voltage SMPS circuits, inverter stages, motor drivers, and other applications where a wiring mistake can instantly damage the MOSFET due to the high voltages involved.

Introduction to IRF840 N-Channel MOSFET

The IRF840 is a high-voltage N-channel enhancement-mode power MOSFET widely used in SMPS primary stages, inverter circuits, offline power supplies, and high-voltage switching applications. It combines a 500 V drain-source rating with fast switching capability, making it a strong choice for designers working on AC mains–powered converters, high-voltage DC supplies, and other demanding power electronics. Its TO-220 body gives good thermal performance while maintaining cost-effectiveness and easy PCB integration.

IRF840 N-Channel MOSFET

Pinout of IRF840

Pin Configuration of IRF840 Pinout

The IRF840 pinout is based on the highly common TO-220 standard with three leads arranged as:

The metal tab is also connected internally to the drain, so proper insulation is required if mounting it on a grounded heatsink.

Key Features of IRF840 MOSFET

• High-voltage capability suitable for AC mains applications
• Fast switching for SMPS and inverter topologies
• Strong avalanche energy handling
• Rugged TO-220 package for superior heat dissipation
• Easy gate drive requirements relative to bipolar devices
• Suitable for medium-power conversion and motor-control applications

Datasheet and Specifications of IRF840 MOSFET

• VDS (Drain-Source Voltage): 500 V
• VGS (Gate-Source Voltage): ±20 V
• ID (Continuous Drain Current): 8 A
• IDM (Pulsed Drain Current): 32 A
• RDS(on) (Drain-Source On-Resistance): 0.85 Ω
• Ptot (Total Power Dissipation): 125 W
• Tstg (Storage Temperature Range): −65°C to +150°C
• TJ (Junction Temperature): 150°C
• Package: TO-220
• Pin Configuration: G – D – S (front view)

Working Principle of IRF840 MOSFET

The IRF840 operates as a voltage-controlled switch. When a positive voltage is applied between the gate and source above the threshold level, an n-channel forms, enabling current to flow from drain to source. This makes the device ideal for PWM switching, on/off control, and high-voltage conversion. Its fast switching behavior reduces switching losses, improving efficiency in SMPS and inverter designs. However, the MOSFET must be driven with a proper gate voltage (typically around 10–12 V) to minimize conduction losses.

More Circuit Layouts

Applications of IRF840 MOSFET

• SMPS primary-side switching (flyback, forward converters)
• High-voltage inverters and DC–AC conversion
• LED drivers and lamp ballasts
• High-voltage DC power supplies
• Induction heaters and high-frequency drivers
• Motor control circuits (medium power)
• Battery chargers and offline AC-powered systems

Equivalent and Alternative MOSFETs

Suitable alternatives with similar ratings (verify datasheet before replacement):

• IRF740 (lower current, similar voltage)
• IRF830/IRF820 (lower current/voltage options depending on requirement)
• STF10N50, 2SK1119, or similar 500 V MOSFETs
• IRFP series for higher current demands (different package)

Always verify RDS(on), ID, and thermal limits before substituting.

Frequently Asked Questions (FAQ)

Q1: What is the IRF840 pinout?
It follows Gate – Drain – Source (G-D-S) in TO-220, with the tab connected to the drain.

Q2: Can IRF840 run directly from microcontroller GPIO pins?
No. It requires a proper gate driver or at least a buffer to provide sufficient gate charge.

Q3: Is IRF840 suitable for high-frequency SMPS?
Yes, but at very high frequencies switching losses rise. For >100 kHz operation, use MOSFETs designed with lower gate charge.

Q4: Does IRF840 require a heatsink?
Yes — for medium to high power usage, heatsinking is mandatory due to its high dissipation capability.

Conclusion

The IRF840 is a robust and versatile high-voltage N-channel MOSFET ideal for SMPS, inverters, and high-voltage power control. Its 500 V capability, reliable switching performance, and TO-220 thermal characteristics make it a dependable choice for designers. Correct usage of the IRF840 pinout, proper gate drive, and adequate heatsinking ensures long-term and safe performance in demanding power electronics environments.

Datasheet & Pinout of IRF840 N-Channel MOSFET

Click the following Button to download the datasheet of IRF840 MOSFET :

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