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Home > Products > Discrete Semiconductor Products > Transistors > Bipolar (BJT) > Single Bipolar Transistors

STMicroelectronics BUF420M

Name: BUF420M
Brand: STMicroelectronics
SKU: BUF420M
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: BUF420M

Manufacturer:: STMicroelectronics

Category:: Single Bipolar Transistors

Package:: TO-204AA, TO-3

Datasheet:: BUF420M.pdf

Description:: TRANS NPN 450V 30A TO-3

Quantity:: RFQ Add To RFQ list

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Inventory:8,740

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Product details

Overview

BUF420M from STMicroelectronics is a high-voltage, fast-switching NPN power transistor fabricated in High Voltage Multi Epitaxial Planar technology with cellular emitter and planar edge termination. It delivers 450 V V_CEO, 30 A I_C, 275 W P_tot, <1 µs storage time (t_s), and 70–150 A/µs dI_C/dt - enabling robust operation in hard-switched SMPS and motor control inverters.

For engineers reviewing the BUF420M datasheet, BUF420M pinout, BUF420M application, or BUF420M equivalent, key selection criteria include RBSOA width under inductive switching, snubberless V_CEW = 500 V at T_C = 125 °C, low base-drive requirement (I_B = 1 A for 10 A I_C), and thermal resistance of 0.63 °C/W.

Technical Context

The BUF420M employs a cellular emitter structure and planar edge termination to simultaneously extend reverse-biased safe operating area (RBSOA) and minimize minority-carrier storage time. Its design targets hard-switched topologies where voltage overshoot and secondary breakdown must be suppressed without snubbers.

It operates with V_CE(sat) = 0.8 V (I_C = 10 A, I_B = 1 A) and V_BE(sat) = 0.9 V under same conditions, supporting efficient gate/base drive staging. The 0.63 °C/W R_thj-case enables high-power dissipation in TO-3(R) metal packages with minimal heatsink mass.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	450 V - maximum collector-emitter voltage with open base; defines hard-switching headroom in flyback and forward converters
I_C	30 A continuous - supports 1–2 kW power stages in industrial motor drives and telecom SMPS
t_s (inductive)	1 µs at T_C = 25 °C - enables >100 kHz switching in snubberless configurations
dI_C/dt	70–150 A/µs - determines turn-off di/dt capability and EMI filter sizing
R_thj-case	0.63 °C/W - allows 275 W dissipation with ≤175 °C junction rise above 25 °C case temperature
V_CEW	500 V at T_C = 125 °C - maximum snubberless blocking voltage under worst-case thermal stress
V_CE(sat)	0.8 V @ I_C = 10 A, I_B = 1 A - sets conduction loss baseline for base-driven switch designs

Pinout & Package

BUF420M is housed in a TO-3 (version "R") metal can package with isolated collector, standard pin assignment, and screw-mount mechanical interface. Thermal path is direct from die to case via copper baseplate.

Pin/Terminal	Circuit Role	Design Meaning
Collector (Case)	Main current return path and thermal interface	Electrically connected to metal can; must be insulated from heatsink unless system ground reference permits
Base (Lead 1)	Control terminal for minority-carrier injection	Low-impedance input requiring ~1 A drive for full 10 A conduction; sensitive to negative V_BE transients
Emitter (Lead 2)	Current source output and reference node	Serves as common return for load and base drive; layout critical for minimizing L_EMITTER during switching

Key Features

Feature	Design Value
Cellular Emitter Structure	Enables uniform current distribution and reduced local hot-spot risk during overcurrent events
Planar Edge Termination	Extends RBSOA by suppressing premature edge breakdown at 850 V V_CEV
Low Base-Drive Requirement	I_B = 1 A suffices for 10 A I_C, reducing driver stage complexity and power loss
Wide RBSOA	Supports unclamped inductive switching up to 500 V without snubber network
Minimum Lot-to-Lot Spread	Guarantees consistent t_s, V_CE(sat), and gain across production batches for BOM stability

Applications

Switch Mode Power Supplies

Motor Control Inverters

Use Scenario: Primary-side switch in 500–800 W offline flyback or forward converters operating at 50–100 kHz.

IC Role / Device Role / Timing Role: Main power switch handling high dV/dt and repetitive avalanche stress during transformer reset.

Use Value: V_CEW = 500 V enables snubberless operation, reducing component count and improving efficiency at full load.

Use Scenario: Upper-leg IGBT replacement in 3-phase 7.5 kW industrial motor drives with discrete gate control.

IC Role / Device Role / Timing Role: Hard-switched NPN switch in totem-pole output stage, commutating inductive motor currents.

Use Value: t_s < 1 µs and dI_C/dt > 70 A/µs allow clean turn-off with minimal cross-conduction loss in 60 Hz–2 kHz PWM.

High-Voltage DC-DC Converters

Capacitor Discharge Circuits

Use Scenario: Step-up converter in battery-powered test equipment generating 400 V DC from 48 V input.

IC Role / Device Role / Timing Role: Sustained conduction switch managing high V_CE and moderate I_C with tight thermal constraints.

Use Value: R_thj-case = 0.63 °C/W permits compact heatsinking while maintaining T_j < 150 °C at 200 W dissipation.

Use Scenario: Pulse discharge switch in laser flashlamp drivers requiring sub-microsecond turn-on and high peak current.

IC Role / Device Role / Timing Role: Single-pulse high-current switch triggered by narrow base pulse, operating in linear region briefly.

Use Value: I_CM = 60 A and t_f = 0.05 µs ensure rapid energy delivery with minimal pulse distortion.

Equivalent & Alternatives

The following parts are listed as comparable options for similar high-voltage NPN power transistor applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
BU508A	V_CEO = 1000 V, t_s = 3 µs, R_thj-case = 0.85 °C/W	Higher voltage margin but slower switching; suited for lower-frequency (<30 kHz) SMPS	Choose when V_CE stress exceeds 450 V but dI_C/dt demands are modest
2SD1762	V_CEO = 400 V, t_s = 0.8 µs, P_tot = 150 W	Narrower voltage rating but faster turn-off; limited to <1 kW designs with active clamping	Prefer when thermal budget is constrained and V_CE peaks stay below 400 V

Compared with BU508A and 2SD1762, BUF420M uniquely balances 450 V blocking, sub-1 µs storage time, and 275 W dissipation - making it optimal for snubberless 50–100 kHz industrial SMPS where both voltage headroom and switching speed are critical.

Availability

BUF420M is available at Aetrix Electronics and suitable for switch mode power supplies, motor control inverters, and high-voltage DC-DC converters requiring stable component supply and long-term industrial lifecycle support.

Supply support for BUF420M 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 BUF series was developed specifically for high-frequency, high-voltage power conversion - emphasizing RBSOA integrity, low base-drive burden, and lot-to-lot parametric consistency in discrete power transistors.

FAQ

Is BUF420M still in active production?

No - BUF420M is marked "Obsolete Product(s)" in its official STMicroelectronics datasheet (Rev. March 2002). However, Aetrix Electronics maintains legacy inventory with full traceability and supports extended-life procurement for industrial maintenance and repair programs.

What is the recommended base drive circuit for BUF420M?

A dedicated low-impedance base driver delivering ±5 V with ≥1.5 A peak sink/source capability is required. Use a negative V_BB = −5 V and R_BB = 0.6 Ω for fast turn-off; avoid RC networks that increase t_s. Layout must minimize base-emitter loop inductance to prevent oscillation.

Can BUF420M replace an IGBT in motor control?

Yes - in hard-switched 3-phase inverters up to 7.5 kW, BUF420M provides comparable V_CE(sat) and superior dI_C/dt vs. early-generation 600 V IGBTs. However, it requires precise base drive timing and lacks built-in short-circuit ruggedness - external desaturation protection remains essential.

Does BUF420M require a snubber network?

Not necessarily - its V_CEW = 500 V at T_C = 125 °C allows snubberless operation in properly designed inductive loads with controlled dI_C/dt and clamped V_CE peaks. Snubbers remain advisable for designs exceeding 450 V V_CE or with poor layout-induced ringing.

BUF420M Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

Package/Case:: TO-204AA, TO-3

Packaging:: Tube

Product Status:: Obsolete

Transistor Type:: NPN

Current - Collector (Ic) (Max):: 30 A

Voltage - Collector Emitter Breakdown (Max):: 450 V

Vce Saturation (Max) @ Ib, Ic:: 500mV @ 4A, 20A

Current - Collector Cutoff (Max):: -

DC Current Gain (hFE) (Min) @ Ic, Vce:: -

Power - Max:: 275 W

Frequency - Transition:: -

Operating Temperature:: 200°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: TO-3

BUF420M FAQ

1.How can I place an order for BUF420M through Aetrix?

Please submit a Request for Quotation (RFQ) for BUF420M 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 BUF420M reliable?

The price and inventory of BUF420M are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BUF420M is usually 5 days.

3.What payment methods are accepted for BUF420M?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BUF420M transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for BUF420M?

BUF420M orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your BUF420M 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 BUF420M?

For technical support, including BUF420M datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BUF420M requirements.

6.How does Aetrix verify that BUF420M is sourced from the original manufacturer or authorized distributors?

All BUF420M 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 BUF420M meets industry standards.

7.What is the process for return or replacement of BUF420M?

All BUF420M units undergo pre-shipment inspection (PSI). If there is an issue with BUF420M, 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 BUF420M part is unused and in its original packaging.

Return procedure for BUF420M:

1.Submit a request within 90 days.

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

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