Description
The IRF634 is a high-voltage N-Channel Power MOSFET designed for high-speed switching applications. It bridges the gap between low-voltage electronics and high-voltage power systems, providing a robust solution for systems requiring up to 250V blocking capability.
Key Specifications
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Transistor Type: N-Channel MOSFET
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Drain-Source Voltage ($V_{DS}$): 250 V
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Continuous Drain Current ($I_D$): 8.1 A (at $25^{\circ}\text{C}$)
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On-Resistance ($R_{DS(on)}$): $0.45 \ \Omega$ (Max)
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Power Dissipation ($P_D$): 74 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: IRF634 vs. IRF630N
While both are 200V+ N-Channel MOSFETs in the TO-220 package, the IRF634 is optimized for slightly higher voltage headroom.
| Feature | IRF634 | IRF630N |
| Max $V_{DS}$ | 250 V | 200 V |
| Max $I_D$ | 8.1 A | 9 A |
| $R_{DS(on)}$ | $0.45 \ \Omega$ | $0.3 \ \Omega$ |
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Selection Insight: You would choose the IRF634 specifically when your application rail voltage exceeds 200V (up to 250V), as the extra voltage margin is necessary to prevent breakdown.
Common Applications
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Switching Power Supplies: Used in converters where input voltages reach up to 250V.
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DC-DC Converters: Suitable for boost converters that step up lower voltages to higher levels.
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Solenoid and Relay Drivers: Excellent for driving high-voltage DC coils that are common in industrial automation.
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Motor Control: Used in moderate-power motor speed controllers for higher voltage DC motors.
Usage Best Practices
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Gate Drive: To ensure the MOSFET fully transitions to its $0.45 \ \Omega$ state, use a gate-source voltage ($V_{GS}$) of 10V. Driving the gate with lower voltages (e.g., 3.3V or 5V logic) will result in high resistance, overheating, and potentially destroying the device.
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Thermal Management: The device is rated for 74W total dissipation, but in a TO-220 package, you should aim to keep dissipation well below this limit. Always use a proper heatsink and thermal grease.
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Transient Protection: Because the IRF634 is often used in high-voltage switching, inductive spikes are a constant threat. Place a snubber circuit or a TVS diode across the Drain and Source to suppress voltage spikes that could exceed the 250V rating.

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