Description
The IRF640N is a high-performance N-Channel Power MOSFET that provides a great balance between high voltage blocking capability and solid current-handling capacity. It is an enhanced version of the original IRF640, offering lower on-resistance and faster switching speeds.
Key Specifications
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Transistor Type: N-Channel MOSFET
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Drain-Source Voltage ($V_{DS}$): 200 V
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Continuous Drain Current ($I_D$): 18 A (at $25^{\circ}\text{C}$)
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On-Resistance ($R_{DS(on)}$): $0.15 \ \Omega$ (Max)
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Power Dissipation ($P_D$): 140 W
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Package Type: TO-220
Pinout Configuration
When looking at the front of the TO-220 package (the metal tab is at the top) with the pins pointing down, the pins from left to right are:
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Gate (G)
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Drain (D)
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Source (S)
Comparison: IRF640N vs. IRFP240/250
While the IRF640N is a TO-220 device, it is often compared to the larger TO-247 devices like the IRFP240 or IRFP250 because they all share a 200V rating.
| Feature | IRF640N | IRFP240 | IRFP250 |
| Package | TO-220 | TO-247 | TO-247 |
| Max Current ($I_D$) | 18 A | 20 A | 30 A |
| $R_{DS(on)}$ | $0.15 \ \Omega$ | $0.18 \ \Omega$ | $0.075 \ \Omega$ |
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When to choose the IRF640N: It is ideal for space-constrained designs where you need 200V blocking but do not require the massive thermal dissipation or extra current capacity of the larger TO-247 packages.
Common Applications
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DC-DC Converters: Frequently used in high-voltage buck or boost converters.
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Motor Control: Suitable for driving DC motors in applications where back-EMF spikes might exceed the safety margins of lower-voltage MOSFETs.
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Uninterruptible Power Supplies (UPS): Used in medium-power inverter stages.
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Class D Audio Amplifiers: Its fast switching characteristics make it a viable candidate for high-efficiency audio stages.
Usage Best Practices
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Gate Driving: To achieve the rated $0.15 \ \Omega$ resistance, you must drive the Gate with a full 10V. Using a 5V microcontroller pin directly will not fully saturate the MOSFET, leading to significant heat generation. A gate driver IC or a small transistor-based level shifter is recommended for optimal performance.
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Heat Management: Even though it is more efficient than older models, at 18A, it will produce heat. Ensure it is securely mounted to an appropriately sized heatsink.
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Parasitic Oscillation: MOSFETs with fast switching times can sometimes oscillate if there is significant inductance in the gate path. Always place a $10 \ \Omega$ to $47 \ \Omega$ resistor in series with the gate, mounted as close to the MOSFET as possible, to dampen these oscillations.
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