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

onsemi BD158STU

Name: BD158STU
Brand: onsemi
SKU: BD158STU
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: BD158STU

Manufacturer:: onsemi

Category:: Single Bipolar Transistors

Package:: TO-225AA, TO-126-3

Datasheet:: BD158STU.pdf

Description:: TRANS NPN 300V 0.5A TO-126-3

Quantity:: RFQ Add To RFQ list

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Product details

Overview

BD158STU from Fairchild Semiconductor is an NPN epitaxial silicon transistor designed for low-power fast-switching output stages in audio and TV applications. It features V_CEO = 300 V, I_C = 0.5 A (DC), P_C = 20 W at T_C = 25°C, h_FE = 30–240 (V_CE = 10 V, I_C = 50 mA), and TO-126 package with emitter-collector-base pinout. It is used in TV/audio output amplifier stages requiring robust voltage handling and moderate power switching.

For engineers reviewing the BD158STU datasheet, pinout, applications, or equivalent options, key selection considerations include collector-emitter breakdown voltage (300 V), DC current gain range, safe operating area under pulsed conditions, thermal derating behavior, and compatibility with TO-126 heatsink mounting in linear amplifier output stages.

Technical Context

This device operates as a medium-voltage, medium-current NPN bipolar junction transistor optimized for linear and switching operation in analog output stages. Its 300 V V_CEO rating and 350 V V_CBO support high-swing audio and deflection circuitry, while its 20 W power dissipation at case temperature 25°C enables use with modest heatsinking.

The BD158STU exhibits h_FE of 30–240 at V_CE = 10 V and I_C = 50 mA, and maintains low V_CE(sat) under I_C ≤ 0.5 A, supporting efficient Class AB push-pull configurations. Its safe operating area (SOA) is defined up to 1 ms pulse width with derating above 25°C case temperature.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	300 V - Maximum continuous collector-emitter voltage before breakdown; enables use in 200–250 V rail audio output stages.
I_C (DC)	0.5 A - Continuous collector current limit; defines maximum sustained output current in linear amplifiers.
P_C (T_C=25°C)	20 W - Maximum power dissipation at case temperature 25°C; requires heatsink for >1 W continuous operation.
h_FE	30–240 - DC current gain range at V_CE = 10 V, I_C = 50 mA; supports bias stability across production lots.
V_CE(sat)	≤1.6 V @ I_C = 0.5 A, I_B = 0.1 A - Low saturation voltage ensures minimal power loss in switching mode.
T_J max	150°C - Maximum junction temperature; sets upper thermal limit for reliability in sealed enclosures.

Pinout & Package

BD158STU is housed in a TO-126 plastic package with standard lead configuration: Pin 1 = Emitter, Pin 2 = Collector, Pin 3 = Base. The collector tab is electrically connected to Pin 2 and serves as primary thermal path.

Pin/Terminal	Circuit Role	Design Meaning
1 (Emitter)	Emitter terminal	Reference node for base drive and current return; internally bonded to emitter region, not isolated from case.
2 (Collector)	Collector terminal / Heatsink tab	Main power output node; electrically tied to metal tab for direct heatsink mounting and thermal conduction.
3 (Base)	Control input	Current-driven control node; requires external base resistor to set operating point in linear or saturated mode.

Key Features

Feature	Design Value
High V_CBO	325 V - Enables operation in high-voltage sweep and deflection circuits without avalanche stress.
Fast switching capability	Specified in typical characteristics (Fig. 3 SOA); supports <1 ms pulse operation up to 1 A peak current.
TO-126 mechanical standardization	Compatible with industry-standard mounting holes and heatsink clamps; simplifies mechanical design reuse.
Low I_CBO	100 µA @ V_CB = 325 V - Ensures stable bias under high-voltage standby conditions in TV horizontal output stages.

Applications

TV Horizontal Output Stage	Audio Power Amplifier Driver
Use Scenario: Drives flyback transformer in CRT television horizontal deflection circuits with 15.734 kHz switching and 300 V peak collector swing. IC Role / Device Role / Timing Role: NPN switching transistor operating in saturated/active transition zone; handles high-voltage retrace pulses and linear scan ramp. Use Value: 300 V V_CEO and 325 V V_CBO prevent breakdown during flyback overshoot; TO-126 tab enables direct heatsink attachment for transient thermal management.	Use Scenario: Serves as driver stage in discrete Class AB audio power amplifiers delivering up to 10 W into 8 Ω loads. IC Role / Device Role / Timing Role: Linear amplifier transistor biased in active region; provides current gain and voltage swing to final output pair. Use Value: h_FE range (30–240) allows predictable DC bias design; low V_CE(sat) minimizes quiescent power loss and improves thermal efficiency.
Radio RF Final Amplifier	Industrial Signal Generator Output
Use Scenario: Used in AM/FM broadcast receiver final IF or detector-stage amplifiers operating up to 100 MHz. IC Role / Device Role / Timing Role: Medium-frequency linear amplifier; configured in common-emitter topology with tuned collector load. Use Value: f_T not specified in source, but typical BD15x family f_T > 3 MHz supports IF amplification; 5 V V_EB rating permits stable base bias networks.	Use Scenario: Delivers calibrated low-distortion sine/square wave outputs (up to 20 Vpp) in benchtop signal generators. IC Role / Device Role / Timing Role: Output buffer transistor driving 50 Ω or high-Z loads; operated in linear region with feedback stabilization. Use Value: 20 W power rating and 150°C T_J allow sustained output into reactive loads; TO-126 package supports precise thermal calibration.

TV Horizontal Output Stage

Audio Power Amplifier Driver

Use Scenario: Drives flyback transformer in CRT television horizontal deflection circuits with 15.734 kHz switching and 300 V peak collector swing.

IC Role / Device Role / Timing Role: NPN switching transistor operating in saturated/active transition zone; handles high-voltage retrace pulses and linear scan ramp.

Use Value: 300 V V_CEO and 325 V V_CBO prevent breakdown during flyback overshoot; TO-126 tab enables direct heatsink attachment for transient thermal management.

Use Scenario: Serves as driver stage in discrete Class AB audio power amplifiers delivering up to 10 W into 8 Ω loads.

IC Role / Device Role / Timing Role: Linear amplifier transistor biased in active region; provides current gain and voltage swing to final output pair.

Use Value: h_FE range (30–240) allows predictable DC bias design; low V_CE(sat) minimizes quiescent power loss and improves thermal efficiency.

Radio RF Final Amplifier

Industrial Signal Generator Output

Use Scenario: Used in AM/FM broadcast receiver final IF or detector-stage amplifiers operating up to 100 MHz.

IC Role / Device Role / Timing Role: Medium-frequency linear amplifier; configured in common-emitter topology with tuned collector load.

Use Value: f_T not specified in source, but typical BD15x family f_T > 3 MHz supports IF amplification; 5 V V_EB rating permits stable base bias networks.

Use Scenario: Delivers calibrated low-distortion sine/square wave outputs (up to 20 Vpp) in benchtop signal generators.

IC Role / Device Role / Timing Role: Output buffer transistor driving 50 Ω or high-Z loads; operated in linear region with feedback stabilization.

Use Value: 20 W power rating and 150°C T_J allow sustained output into reactive loads; TO-126 package supports precise thermal calibration.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
MJD127G	V_CEO = 100 V, I_C = 2 A, TO-220 package, higher current but lower voltage rating.	Suitable for low-voltage industrial motor drivers, not TV flyback or high-rail audio.	Select when >1 A DC current required and V_CEO ≤ 100 V suffices; requires different heatsink footprint.
BD237	V_CEO = 60 V, h_FE = 25–250, TO-126, lower voltage but similar gain and package.	Used in low-voltage audio preamp and relay driver stages; insufficient for 300 V TV output.	Choose only for sub-60 V supply rails where BD158STU's voltage margin is unnecessary.

Compared with BD158STU, MJD127G trades voltage headroom for higher current and thermal mass, while BD237 retains TO-126 compatibility but sacrifices 240 V of collector-emitter standoff-making BD158STU uniquely suited for legacy CRT and high-rail analog output designs.

Availability

BD158STU is available at Aetrix Electronics and suitable for TV horizontal deflection circuits, audio power amplifier drivers, RF final stages, and industrial signal generator outputs requiring stable component supply and long-lifecycle support.

Supply support for BD158STU 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

Fairchild Semiconductor was a U.S.-based semiconductor company specializing in power management, analog, and discrete devices before its acquisition by ON Semiconductor in 2016.

The BD158STU belongs to Fairchild's legacy BD157/158/159 series of NPN transistors engineered for reliable, cost-effective linear and switching output stages in consumer audio/video equipment.

FAQ

What is the maximum collector-emitter voltage rating for BD158STU?

The BD158STU has a guaranteed minimum V_CEO of 300 V at T_C = 25°C, as specified in the Absolute Maximum Ratings table. This rating applies under DC conditions and defines the upper limit for safe continuous collector-emitter voltage swing. Exceeding this value risks avalanche breakdown and permanent device failure. The BD158STU datasheet confirms this parameter with test condition I_C = 1 mA, I_B = 0.

Is BD158STU suitable for linear amplifier applications?

Yes, BD158STU is explicitly designed for linear amplifier output stages, as stated in its "Low Power Fast Switching Output Stages" application note. Its h_FE range (30–240), low V_CE(sat), and defined SOA support stable Class AB operation. The BD158STU datasheet includes typical characteristics for DC current gain and saturation voltage-key parameters for linear bias design.

What package type does BD158STU use, and how is it mounted?

BD158STU uses the TO-126 plastic package with three leads: Pin 1 = Emitter, Pin 2 = Collector (electrically connected to the metal tab), Pin 3 = Base. Mounting requires insulating hardware if the heatsink is grounded, as the collector tab is live. The BD158STU package dimensions (16.10 × 13.06 mm body, 14.20 mm max height) are fully documented in the mechanical drawing.

Does BD158STU have a specified transition frequency (f_T)?

No, the BD158STU datasheet does not list f_T or small-signal frequency response data. It is characterized for DC and pulsed switching performance (e.g., SOA, V_CE(sat), h_FE), not RF gain-bandwidth. For high-frequency amplification, designers should refer to Fairchild's RF-optimized transistors; the BD158STU is intended for audio, IF, and deflection frequencies where f_T is not a limiting factor.

Can BD158STU replace BD157 or BD159 in a design?

BD158STU is part of the BD157/158/159 family and shares identical pinout, package, and basic characteristics-but differs in voltage ratings: BD157 (250 V V_CEO), BD158STU (300 V), BD159 (350 V). Substituting BD158STU for BD157 is generally safe if 300 V margin is acceptable; replacing BD159 requires verification that 300 V meets system overvoltage requirements. Always confirm h_FE and SOA alignment per application.

BD158STU Specifications

Product attributes: Attribute value

Manufacturer:: onsemi

Series:: -

Package/Case:: TO-225AA, TO-126-3

Packaging:: Tube

Product Status:: Obsolete

Transistor Type:: NPN

Current - Collector (Ic) (Max):: 500 mA

Voltage - Collector Emitter Breakdown (Max):: 300 V

Vce Saturation (Max) @ Ib, Ic:: -

Current - Collector Cutoff (Max):: 100µA (ICBO)

DC Current Gain (hFE) (Min) @ Ic, Vce:: 30 @ 50mA, 10V

Power - Max:: 20 W

Frequency - Transition:: -

Operating Temperature:: -

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: TO-126-3

BD158STU FAQ

1.How can I place an order for BD158STU through Aetrix?

Please submit a Request for Quotation (RFQ) for BD158STU 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 BD158STU reliable?

The price and inventory of BD158STU are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BD158STU is usually 5 days.

3.What payment methods are accepted for BD158STU?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BD158STU transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for BD158STU?

BD158STU orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your BD158STU 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 BD158STU?

For technical support, including BD158STU datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BD158STU requirements.

6.How does Aetrix verify that BD158STU is sourced from the original manufacturer or authorized distributors?

All BD158STU 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 BD158STU meets industry standards.

7.What is the process for return or replacement of BD158STU?

All BD158STU units undergo pre-shipment inspection (PSI). If there is an issue with BD158STU, 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 BD158STU part is unused and in its original packaging.

Return procedure for BD158STU:

1.Submit a request within 90 days.

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

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