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

STMicroelectronics ST8812FX

Name: ST8812FX
Brand: STMicroelectronics
SKU: ST8812FX
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: ST8812FX

Manufacturer:: STMicroelectronics

Category:: Single Bipolar Transistors

Package:: ISOWATT218FX

Datasheet:: ST8812FX.pdf

Description:: TRANS NPN 600V 7A ISOWATT-218FX

Quantity:: RFQ Add To RFQ list

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Product details

Overview

ST8812FX from STMicroelectronics is a high-voltage fast-switching NPN power transistor manufactured using Multi Epitaxial Planar technology, featuring 600 V V_CEO, 7 A I_C, 50 W P_TOT, and 2.5 °C/W R_thJ-case. It delivers tight h_FE control (4.5–9), 1.5 V V_CE(sat) at 4 A/1.2 A, and 1.6 µs storage time for CRT TV switch-mode power supplies.

For engineers reviewing the ST8812FX datasheet, ST8812FX pinout, ST8812FX application, or ST8812FX equivalent, this device is selected for high-reliability flyback converter primary switches where high V_CEO, wide RBSOA, and fast inductive switching under 480 V clamp are critical design requirements.

Technical Context

The ST8812FX employs a cellular emitter structure with planar edge termination and deep base diffusion to achieve wide reverse-biased safe operating area (RBSOA) and high-speed switching. Its 1150 V V_CBO and 600 V V_CEO(sus) support operation in high-voltage flyback topologies with margin against voltage spikes.

Designed for hard-switched inductive loads, it exhibits 1.6 µs storage time and 120 ns fall time under 480 V clamping with 220 µH load, enabling stable operation in CRT horizontal deflection circuits without snubber overdesign.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	600 V - Sustains full line-referred voltage in 230 VAC SMPS with safety margin
I_C	7 A continuous - Supports >200 W output power in single-transistor flyback designs
V_CE(sat)	1.5 V @ 4 A/1.2 A - Limits conduction loss to <6 W at rated current
h_FE	4.5–9 @ 5 A/1 V - Enables predictable base drive sizing with low gain variation
R_thJ-case	2.5 °C/W - Allows 50 W dissipation with ≤125°C case temperature rise
t_s	1.6 µs - Reduces switching loss during turn-off in inductive CRT deflection loads
V_isol	2500 V RMS - Permits direct mounting to heatsink without insulating washer in UL-compliant designs

Pinout & Package

Package: ISOWATT218FX - Fully insulated, U.L.-compliant power package with integrated heatsink interface and 5.6 g mass; mounting torque: 0.55 Nm recommended.

Pin/Terminal	Circuit Role	Design Meaning
1 (Collector)	Main high-current drain path	Connected to primary winding of flyback transformer; carries full switching current and voltage stress
2 (Base)	Current-controlled input terminal	Receives low-impedance drive signal; requires ~1.2 A peak for full saturation at 4 A collector current
3 (Emitter)	Reference node and current return	Connected to ground reference; forms common return for base drive and output sensing in grounded-emitter configuration

Key Features

Feature	Design Value
Cellular Emitter Structure	Enables uniform current distribution and prevents localized thermal runaway during high-dV/dt switching
Planar Edge Termination	Extends breakdown voltage margin and improves long-term reliability under repetitive overvoltage stress
Tight h_FE Control (4.5–9)	Reduces base drive circuit variability and simplifies gate driver IC selection in discrete BJT-based SMPS
Wide RBSOA	Supports unclamped inductive switching up to 600 V × 7 A without secondary breakdown in CRT horizontal output stages
UL-Compliant Insulation	Eliminates need for mica washers or silicone pads when mounted directly to metal chassis or heatsink

Applications

CRT TV Horizontal Deflection

Flyback Converter Primary Switch

Use Scenario: Horizontal scanning output stage in analog CRT television sets requiring precise timing and high peak current pulses.

IC Role / Device Role / Timing Role: High-voltage NPN switch controlling flyback transformer primary current; synchronized to horizontal sync signal.

Use Value: 1.6 µs storage time and 120 ns fall time minimize dead-time loss and enable stable 15.734 kHz operation with minimal overshoot.

Use Scenario: Primary-side switching element in offline AC/DC flyback converters for consumer electronics power supplies.

IC Role / Device Role / Timing Role: Main energy transfer switch turning on/off transformer primary to regulate output voltage via duty cycle.

Use Value: 600 V V_CEO and 1150 V V_CBO provide margin against reflected transients in universal-input (85–265 VAC) designs.

High-Voltage DC-DC Converter

Industrial HV Power Supply

Use Scenario: Step-up DC-DC converter in battery-powered test equipment generating 400–600 V outputs.

IC Role / Device Role / Timing Role: Hard-switched NPN transistor in boost or flyback topology operating at fixed frequency with current-mode control.

Use Value: 2.5 °C/W thermal resistance enables air-cooled operation at 35 W dissipation, reducing heatsink size by 40% vs. comparable TO-247 devices.

Use Scenario: Line-powered industrial power supply for PLC I/O modules requiring reinforced isolation and long service life.

IC Role / Device Role / Timing Role: Primary-side switch in isolated flyback with optocoupler feedback and overvoltage protection.

Use Value: 2500 V RMS insulation withstand allows direct heatsink mounting while meeting IEC 61800-5-1 creepage/clearance requirements.

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 = 1500 V, I_C = 12 A, R_thJ-case = 1.7 °C/W, no insulation rating	Higher voltage headroom but requires external insulation; larger footprint (TO-3P)	Preferred where >1 kV blocking is mandatory and heatsink isolation is already implemented
2SD1878	V_CEO = 600 V, I_C = 5 A, R_thJ-case = 3.0 °C/W, non-insulated TO-218	Lower current rating and thermal performance; no built-in isolation	Suitable for lower-power (<150 W) designs where cost is prioritized over mounting simplicity

Compared with BU508A and 2SD1878, the ST8812FX uniquely combines UL-rated insulation, tight h_FE spread, and optimized RBSOA for CRT deflection-making it irreplaceable in legacy TV repair and certified replacement programs requiring drop-in compliance.

Availability

ST8812FX is available at Aetrix Electronics and suitable for CRT TV repair, flyback converter manufacturing, and industrial HV power supply refurbishment requiring stable component supply and long-lifecycle support.

Supply support for ST8812FX 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, digital, and mixed-signal ICs and discrete power devices for automotive, industrial, and consumer markets.

The ST8812FX belongs to ST's high-voltage bipolar power transistor family, engineered specifically for robustness and reliability in CRT horizontal deflection and offline SMPS applications where voltage margin and switching consistency are critical.

FAQ

Is the ST8812FX still in active production?

No-the ST8812FX is marked "Obsolete Product(s)" in its official datasheet (Rev 1, March 2006). However, Aetrix Electronics maintains legacy inventory with full traceability and offers extended lifecycle support including cross-reference validation and controlled distribution for repair and maintenance programs.

What is the maximum safe operating voltage for ST8812FX in continuous conduction mode?

The absolute maximum V_CEO is 600 V with I_B = 0, and V_CBO is 1150 V with I_E = 0. For reliable long-term operation in flyback converters, ST recommends limiting V_CE to ≤480 V under clamped inductive switching conditions per Figure 8 test circuit.

Can ST8812FX be used as a direct replacement for BU2520DX in CRT TV sets?

No-BU2520DX has V_CEO = 1500 V and different h_FE range (6–12); substituting ST8812FX risks premature failure due to insufficient voltage margin in high-line surge conditions. ST8812FX is validated only for designs originally specifying its 600 V rating and 1.5 V V_CE(sat).

Does the ISOWATT218FX package require thermal compound when mounted to a heatsink?

Yes-despite its UL-rated insulation, ST specifies use of thermally conductive compound (e.g., silicone grease or phase-change pad) between the metal flange and heatsink surface to maintain R_thJ-case ≤2.5 °C/W. Mounting without thermal interface increases junction temperature by ≥15°C at full 50 W dissipation.

ST8812FX Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

Package/Case:: ISOWATT218FX

Packaging:: Tube

Product Status:: Obsolete

Transistor Type:: NPN

Current - Collector (Ic) (Max):: 7 A

Voltage - Collector Emitter Breakdown (Max):: 600 V

Vce Saturation (Max) @ Ib, Ic:: 3V @ 800mA, 4A

Current - Collector Cutoff (Max):: 1mA

DC Current Gain (hFE) (Min) @ Ic, Vce:: 4.5 @ 5A, 5V

Power - Max:: 50 W

Frequency - Transition:: -

Operating Temperature:: 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: ISOWATT-218FX

ST8812FX FAQ

1.How can I place an order for ST8812FX through Aetrix?

Please submit a Request for Quotation (RFQ) for ST8812FX 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 ST8812FX reliable?

The price and inventory of ST8812FX are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for ST8812FX is usually 5 days.

3.What payment methods are accepted for ST8812FX?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for ST8812FX transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for ST8812FX?

ST8812FX orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your ST8812FX 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 ST8812FX?

For technical support, including ST8812FX datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your ST8812FX requirements.

6.How does Aetrix verify that ST8812FX is sourced from the original manufacturer or authorized distributors?

All ST8812FX 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 ST8812FX meets industry standards.

7.What is the process for return or replacement of ST8812FX?

All ST8812FX units undergo pre-shipment inspection (PSI). If there is an issue with ST8812FX, 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 ST8812FX part is unused and in its original packaging.

Return procedure for ST8812FX:

1.Submit a request within 90 days.

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

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