IRF840 Datasheet; A complete Introduction to IRF840 is an N-Channel MOSFET

What is an IRF840 MOSFET?

The IRF840 is an N-Channel enhancement mode MOSFET designed for high-speed switching applications. It is part of the HEXFET® family of power MOSFETs manufactured by Vishay Siliconix. The IRF840 offers excellent performance characteristics, including low on-resistance, fast switching speeds, and high current handling capability.

Key Features of the IRF840 MOSFET

N-Channel enhancement mode MOSFET
Low on-resistance (RDS(on))
Fast switching speeds
High current handling capability
Avalanche energy rated
Rugged and reliable design
TO-220AB package

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IRF840 Specifications

Absolute Maximum Ratings

Parameter	Symbol	Value	Unit
Drain-Source Voltage	VDS	500	V
Gate-Source Voltage	VGS	±20	V
Continuous Drain Current at TC = 25°C	ID	8	A
Pulsed Drain Current	IDM	32	A
Maximum Power Dissipation	PD	125	W
Operating Junction Temperature Range	TJ	-55 to +175	°C
Storage Temperature Range	TSTG	-55 to +175	°C

Electrical Characteristics

Parameter	Symbol	Conditions	Min	Typ	Max	Unit
Gate Threshold Voltage	VGS(th)	VDS = VGS, ID = 250µA	2.0	–	4.0	V
Static Drain-Source On-Resistance	RDS(on)	VGS = 10V, ID = 4A	–	0.85	1.2	Ω
Input Capacitance	Ciss	VDS = 25V, VGS = 0V, f = 1MHz	–	1300	–	pF
Output Capacitance	Coss	VDS = 25V, VGS = 0V, f = 1MHz	–	130	–	pF
Reverse Transfer Capacitance	Crss	VDS = 25V, VGS = 0V, f = 1MHz	–	35	–	pF
Turn-On Delay Time	td(on)	VDD = 250V, ID = 8A, VGS = 10V	–	12	–	ns
Rise Time	tr	VDD = 250V, ID = 8A, VGS = 10V	–	66	–	ns
Turn-Off Delay Time	td(off)	VDD = 250V, ID = 8A, VGS = 10V	–	43	–	ns
Fall Time	tf	VDD = 250V, ID = 8A, VGS = 10V	–	32	–	ns

Applications of the IRF840 MOSFET

The IRF840 MOSFET is suitable for a wide range of applications, including:

Switching power supplies
Motor drivers
Inverters
DC-DC converters
Battery chargers
Automotive electronics
Audio amplifiers
Robotics and automation

Switching Power Supplies

The IRF840 is commonly used in switching power supplies due to its fast switching speeds and low on-resistance. It can handle high currents and voltages, making it suitable for both low and high-power applications. The MOSFET’s low gate charge allows for efficient switching, reducing power losses and improving overall efficiency.

Motor Drivers

In motor driver circuits, the IRF840 can be used to control the current flow to the motor windings. Its high current handling capability and fast switching speeds enable precise motor control and efficient operation. The MOSFET’s low on-resistance minimizes power dissipation, allowing for cooler operation and improved system reliability.

Inverters and DC-DC Converters

The IRF840 is well-suited for use in inverters and DC-DC converters. Its high voltage rating and low on-resistance make it ideal for high-voltage applications, such as solar inverters and power conditioning systems. The MOSFET’s fast switching speeds enable efficient power conversion and minimize switching losses.

Battery Chargers and Automotive Electronics

In battery charger circuits and automotive electronics, the IRF840 can be used for power management and switching applications. Its rugged design and high current handling capability make it suitable for demanding environments, such as those found in vehicles. The MOSFET’s low on-resistance helps to minimize power losses and improve charging efficiency.

Audio Amplifiers

The IRF840 can be used in the output stages of audio amplifiers, particularly in Class D amplifiers. Its fast switching speeds and low on-resistance enable efficient power delivery to the speakers while minimizing distortion. The MOSFET’s high current handling capability allows for high-power audio amplification.

IRF840 MOSFET Circuit Design Considerations

When designing circuits using the IRF840 MOSFET, several factors should be considered to ensure optimal performance and reliability:

Gate drive requirements
Power dissipation and thermal management
Switching speed and efficiency
Paralleling multiple MOSFETs
Protection circuitry

Gate Drive Requirements

The IRF840 requires a sufficient gate drive voltage to turn on fully and achieve low on-resistance. A gate-source voltage (VGS) of at least 10V is recommended for optimal performance. The gate driver should be capable of providing the necessary current to charge and discharge the MOSFET’s input capacitance quickly.

Power Dissipation and Thermal Management

Proper thermal management is crucial to ensure the reliable operation of the IRF840 MOSFET. The power dissipation should be kept within the specified limits to prevent overheating and damage to the device. Heatsinks and other cooling methods may be necessary to maintain the junction temperature below the maximum rated value.

Switching Speed and Efficiency

The IRF840’s fast switching speeds contribute to its high efficiency in switching applications. However, the switching speed can be affected by factors such as gate resistance, circuit layout, and parasitic inductances. Careful design and layout techniques, such as minimizing trace lengths and using proper grounding, can help optimize switching performance.

Paralleling Multiple MOSFETs

In high-current applications, multiple IRF840 MOSFETs can be paralleled to increase the current handling capability. When paralleling MOSFETs, it is essential to ensure proper current sharing among the devices. Techniques such as using current balancing resistors or active current sharing circuits can help distribute the current evenly and prevent thermal runaway.

Protection Circuitry

Incorporating protection circuitry into the design can help safeguard the IRF840 MOSFET against over-voltage, over-current, and over-temperature conditions. Examples of protection circuits include snubbers, current limiting resistors, and temperature monitoring devices. These measures can enhance the reliability and longevity of the MOSFET in demanding applications.

Frequently Asked Questions (FAQ)

What is the maximum drain-source voltage rating of the IRF840 MOSFET?
The maximum drain-source voltage rating of the IRF840 is 500V.
What is the typical on-resistance of the IRF840 MOSFET?
The typical on-resistance (RDS(on)) of the IRF840 is 0.85Ω when the gate-source voltage (VGS) is 10V and the drain current (ID) is 4A.
How much continuous drain current can the IRF840 handle?
The IRF840 can handle a continuous drain current (ID) of 8A at a case temperature (TC) of 25°C.
What is the maximum power dissipation of the IRF840 MOSFET?
The maximum power dissipation (PD) of the IRF840 is 125W.
Is the IRF840 suitable for high-speed switching applications?
Yes, the IRF840 is well-suited for high-speed switching applications due to its fast switching speeds and low on-resistance.

Conclusion

The IRF840 N-Channel MOSFET is a versatile and high-performance device widely used in various electronic applications. Its low on-resistance, fast switching speeds, and high current handling capability make it an excellent choice for switching power supplies, motor drivers, inverters, and more. By understanding the IRF840’s specifications, applications, and design considerations, engineers and hobbyists can effectively utilize this MOSFET to design efficient and reliable circuits.