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Home > Products > Discrete Semiconductor Products > Transistors > FETs, MOSFETs > FETs, MOSFETs

Vishay Siliconix IRF840

Name: IRF840
Brand: Vishay Siliconix
SKU: IRF840
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: IRF840

Manufacturer:: Vishay Siliconix

Category:: FETs, MOSFETs

Package:: TO-220-3

Datasheet:: IRF840.pdf

Description:: MOSFET N-CH 500V 8A TO220AB

Quantity:: RFQ Add To RFQ list

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Inventory:3,663

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Product details

Overview

IRF840 from STMicroelectronics is an N-channel enhancement-mode PowerMESH™II MOSFET rated for 500 V drain-source voltage, 8 A continuous drain current at 25°C, and 0.75 Ω typical R_DS(on). It delivers high-speed switching with 3.5 V/ns dv/dt capability, 100% avalanche tested ruggedness, and is optimized for hard-switched SMPS in industrial power supplies.

For engineers reviewing the IRF840 datasheet, IRF840 pinout, IRF840 application, or IRF840 equivalent, key selection criteria include its 500 V blocking rating, 0.75 Ω on-resistance at 10 V gate drive, 29.6 nC total gate charge, TO-220 package thermal resistance (1 °C/W junction-to-case), and unclamped inductive avalanche energy rating of 520 mJ.

Technical Context

This MOSFET employs ST's second-generation PowerMESH™II layout, which improves Ron·area figure of merit while maintaining low gate charge (29.6–39 nC) and fast switching: 10 ns turn-on delay, 21 ns rise time, and 9 ns off-voltage rise time under 400 V/7 A conditions.

It features a built-in body diode with 1.6 V forward voltage at 8 A, 384 ns reverse recovery time, and 2.2 µC reverse recovery charge at 150°C - critical for snubberless flyback and resonant converter designs where diode recovery impacts EMI and efficiency.

Key Specifications

Parameter	Value and Actual Design Meaning
V_DSS	500 V - supports primary-side switching in offline 400 V DC bus and universal-input AC/DC converters
R_DS(on)	0.75 Ω (typ) at V_GS = 10 V - enables low conduction loss at 3.5 A, suitable for <100 W SMPS
I_D (cont)	8 A at T_C = 25°C - defines maximum continuous current before thermal derating begins
Q_g	29.6 nC (min) - determines gate driver strength requirement and switching loss trade-off
E_AS	520 mJ - quantifies single-pulse avalanche energy handling without failure, critical for inductive load transients
dv/dt	3.5 V/ns - ensures immunity to false turn-on during high-slew-rate voltage transients in bridge circuits
R_thj-case	1.0 °C/W - allows direct heatsink mounting for thermal management in compact power stages

Pinout & Package

IRF840 is housed in a standard through-hole TO-220 package with three leads: Gate (pin 1), Drain (pin 2), Source (pin 3). The metal tab is electrically connected to the Drain terminal and must be insulated if mounted to a grounded heatsink.

Pin/Terminal	Circuit Role	Design Meaning
Pin 1 (Left)	Gate	Controls channel conduction; requires ≥10 V drive for full enhancement; gate leakage <100 nA at ±20 V
Pin 2 (Center)	Drain	Main high-voltage power terminal; electrically tied to metal tab; rated for 500 V blocking
Pin 3 (Right)	Source	Reference node for gate drive; carries full load current; body diode anode

Key Features

Feature	Design Value
PowerMESH™II cell architecture	Optimizes R_DS(on) × area trade-off without sacrificing switching speed or ruggedness
100% unclamped inductive avalanche tested	Guarantees operation under worst-case inductive turn-off stress up to 520 mJ per pulse
Minimized gate charge (Q_g = 29.6 nC)	Reduces driver power loss and enables use with low-current gate drivers in cost-sensitive designs
High dv/dt immunity (3.5 V/ns)	Prevents spurious turn-on in half-bridge or LLC configurations with fast voltage transitions
TO-220 mechanical outline	Enables drop-in replacement in legacy power supply PCBs with standardized footprint and mounting hole spacing

Applications

SMPS Primary Switch

Welding Inverter Output Stage

Use Scenario: High-frequency flyback or forward converter operating at 50–100 kHz with universal AC input (85–265 VAC).

IC Role / Device Role / Timing Role: Main power switch controlling energy transfer from primary to secondary; operates in hard-switched mode with zero-voltage switching not required.

Use Value: 500 V rating accommodates reflected output voltage plus leakage spike margin; 0.75 Ω R_DS(on) limits conduction loss below 2 W at 3.5 A RMS.

Use Scenario: DC-link switching stage in IGBT-gated welding inverters delivering 20–30 kHz square-wave output to transformer primary.

IC Role / Device Role / Timing Role: High-voltage, high-current half-bridge switch handling pulsed 30–50 A peak loads with repetitive avalanche stress.

Use Value: 520 mJ E_AS rating sustains repeated inductive turn-off events; 3.5 V/ns dv/dt immunity prevents shoot-through during fast bus transitions.

UPS DC-AC Inverter

Motor Drive Half-Bridge

Use Scenario: Line-interactive UPS converting 360–400 V DC bus to 50/60 Hz sine-wave output via H-bridge modulation.

IC Role / Device Role / Timing Role: Upper-leg switch in full-bridge topology; subjected to high V_DS during dead-time and body-diode conduction.

Use Value: Body diode V_SD = 1.6 V at 8 A reduces conduction loss during freewheeling; 384 ns t_rr minimizes cross-conduction risk in 10–20 kHz PWM.

Use Scenario: Low-cost BLDC or induction motor drive for fans, pumps, or compressors operating at ≤20 kHz PWM frequency.

IC Role / Device Role / Timing Role: Low-side switch in 3-phase inverter leg; handles continuous 5.1 A at 100°C case temperature.

Use Value: R_DS(on) remains stable over temperature (normalized curve shows <15% drift to 150°C); TO-220 package allows direct bolt-down heatsinking.

Equivalent & Alternatives

The following parts are listed as comparable options for similar high-voltage MOSFET switching applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
STP8NK50Z	Zener-protected superjunction MOSFET; 500 V, 7.5 A, 0.75 Ω R_DS(on), but higher Q_g (45 nC)	Better ESD robustness and lower EMI due to softer switching; less suitable for ultra-high-frequency SMPS	Choose when system-level EMI compliance is prioritized over minimal gate drive loss
FQP8N50C	500 V, 8 A, 0.85 Ω R_DS(on), 32 nC Q_g; no avalanche rating specified in datasheet	Lacks guaranteed avalanche energy rating; requires external clamping in inductive loads	Acceptable only in resistive or lightly inductive loads with controlled turn-off dV/dt

Compared with STP8NK50Z and FQP8N50C, IRF840 offers verified 520 mJ avalanche energy and lower gate charge, making it preferable for unclamped inductive switching in cost-sensitive industrial SMPS where ruggedness and driver simplicity are critical.

Availability

IRF840 is available at Aetrix Electronics and suitable for high-voltage switching power supplies, welding inverters, and UPS DC-AC conversion requiring stable component supply across multi-year production cycles.

Supply support for IRF840 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, designing and manufacturing analog, power, microcontroller, and sensor solutions for industrial, automotive, and consumer markets.

The PowerMESH™II MOSFET product line targets high-reliability, medium-power switching applications where ruggedness, predictable avalanche behavior, and thermal stability are essential - especially in industrial power conversion.

FAQ

What is the maximum safe operating voltage for IRF840 in continuous DC operation?

The absolute maximum drain-source voltage (V_DSS) is 500 V with V_GS = 0. For reliable long-term operation, STMicroelectronics recommends limiting V_DS to ≤400 V in continuous DC applications to maintain sufficient margin against transients, temperature-induced drift, and manufacturing tolerances. Derating is mandatory above 25°C case temperature.

Can IRF840 be used without a heatsink in low-duty-cycle applications?

No - even at 25°C ambient, the 125 W total dissipation rating assumes junction-to-case thermal resistance of 1.0 °C/W and direct heatsink contact. Without a heatsink, junction temperature rises rapidly: at 2 A continuous current and 0.85 Ω R_DS(on), power dissipation exceeds 3.4 W, raising T_j >100°C within seconds. A minimum 10 cm² aluminum heatsink is required for sustained operation above 1 A.

Does IRF840 have integrated gate protection diodes?

No - IRF840 has no internal gate protection circuitry. Its gate oxide is rated for ±20 V maximum, and gate-body leakage is specified at ±100 nA. External Zener clamps (e.g., 15 V TVS between gate and source) are strongly recommended in all designs to prevent ESD damage and overvoltage during PCB handling or driver faults.

How does the body diode performance compare to discrete fast recovery diodes?

The IRF840 body diode has V_SD = 1.6 V at 8 A and t_rr = 384 ns at 150°C, with Q_rr = 2.2 µC. While adequate for low-frequency freewheeling, it is slower and less efficient than purpose-built 600 V fast recovery diodes (e.g., STTH8R06: t_rr = 65 ns, V_F = 1.7 V). Use external diodes when operating above 20 kHz or requiring low EMI.

IRF840 Specifications

Product attributes: Attribute value

Manufacturer:: Vishay Siliconix

Series:: -

Package/Case:: TO-220-3

Packaging:: Tube

Product Status:: Obsolete

FET Type:: N-Channel

Technology:: MOSFET (Metal Oxide)

Drain to Source Voltage (Vdss):: 500 V

Current - Continuous Drain (Id) @ 25°C:: 8A (Tc)

Drive Voltage (Max Rds On, Min Rds On):: 10V

Rds On (Max) @ Id, Vgs:: 850mOhm @ 4.8A, 10V

Vgs(th) (Max) @ Id:: 4V @ 250µA

Gate Charge (Qg) (Max) @ Vgs:: 63 nC @ 10 V

Vgs (Max):: ±20V

Input Capacitance (Ciss) (Max) @ Vds:: 1300 pF @ 25 V

FET Feature:: -

Power Dissipation (Max):: 125W (Tc)

Operating Temperature:: -55°C ~ 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: TO-220AB

IRF840 FAQ

1.How can I place an order for IRF840 through Aetrix?

Please submit a Request for Quotation (RFQ) for IRF840 on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.

2.Are the price and stock information for IRF840 reliable?

The price and inventory of IRF840 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for IRF840 is usually 5 days.

3.What payment methods are accepted for IRF840?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for IRF840 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for IRF840?

IRF840 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your IRF840 order is processed, you will receive an email with the shipment details and tracking number.

Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.

5.How can I obtain technical support or documentation for IRF840?

For technical support, including IRF840 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your IRF840 requirements.

6.How does Aetrix verify that IRF840 is sourced from the original manufacturer or authorized distributors?

All IRF840 products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that IRF840 meets industry standards.

7.What is the process for return or replacement of IRF840?

All IRF840 units undergo pre-shipment inspection (PSI). If there is an issue with IRF840, returns or replacements are accepted under the following conditions:

1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.

2.The issue is reported within 90 days of delivery.

3.The IRF840 part is unused and in its original packaging.

Return procedure for IRF840:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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