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

onsemi BD159

Name: BD159
Brand: onsemi
SKU: BD159
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: BD159

Manufacturer:: onsemi

Category:: Single Bipolar Transistors

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

Datasheet:: BD159.pdf

Description:: TRANS NPN 350V 0.5A TO-126

Quantity:: RFQ Add To RFQ list

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Inventory:2,790

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Product details

Overview

BD159 from onsemi is a plastic medium-power silicon NPN transistor rated for 350 V_CEO, 0.5 A continuous collector current, and 20 W total power dissipation at T_C = 25°C. It serves as a line-operated power output stage in consumer electronics including television, radio, and phonograph applications.

For engineers reviewing the BD159 datasheet, pinout, applications, or equivalent options, key selection factors include its high-voltage breakdown (350 V), thermal resistance (6.25°C/W), TO-225 package with collector-connected tab, and suitability for transformerless AC mains designs requiring reliable medium-power switching.

Technical Context

The BD159 operates as a linear or switched NPN bipolar junction transistor with DC current gain (h_FE) ranging from 30 to 240 at I_C = 50 mA and V_CE = 10 V. Its safe operating area is thermally limited at T_C = 25°C and second-breakdown limited under pulsed conditions.

It features a TO-225 package with pins 2 and 4 internally connected to the collector and electrically tied to the metal tab, enabling direct heatsinking. The device is Pb-free and RoHS compliant, with maximum junction temperature of +150°C and storage range from –65°C to +150°C.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	350 V - Withstands 350 V between collector and emitter with base open, enabling use in 230 VAC line-referred circuits without transformer isolation.
I_C (continuous)	0.5 A - Supports sustained output current up to 500 mA, suitable for driver stages in audio output or horizontal deflection circuits.
P_D @ T_C = 25°C	20 W - Delivers high power handling at case temperature ≤25°C; derates linearly at 0.16 W/°C above that point.
R_θJC	6.25 °C/W - Enables efficient heat transfer from junction to case; requires ≥20 cm² heatsink surface for full 20 W operation at ambient.
h_FE	30–240 - Wide DC current gain range allows flexible biasing across production lots and temperature extremes (–55°C to +150°C).
T_J max	+150°C - Maximum allowable junction temperature defines thermal design margin for reliability-critical consumer power stages.

Pinout & Package

BD159 is housed in a TO-225 package (Case 77-09, Style 1) with a metal tab electrically connected to the collector. Pins 2 and 4 are internally shorted to the collector and tab; Pin 1 is emitter; Pin 3 is base.

Pin/Terminal	Circuit Role	Design Meaning
Pin 1	Emitter	Primary current return path; connects to ground or low-side load reference in common-emitter configurations.
Pins 2 & 4	Collector (tab-connected)	High-current output node tied directly to heatsink; must be isolated from chassis unless circuit design permits collector-ground connection.
Pin 3	Base	Current-controlled input terminal; requires external base resistor to limit I_B ≤ 0.25 A for safe operation.

Key Features

Feature	Design Value
Transformerless operation support	Validated for direct AC mains interface due to 350 V_CEO rating and creepage/clearance compliance in TO-225 package.
High reliability power rating	20 W dissipation at T_C = 25°C with defined derating curve ensures stable lifetime performance in enclosed consumer enclosures.
Pb-free and RoHS compliant	Meets EU Directive 2011/65/EU; "G" suffix denotes lead-free plating and soldering compatibility per ON Semiconductor Soldering Manual.
Thermally optimized package	TO-225 metal tab provides low R_θJC (6.25°C/W), enabling compact heatsink integration without thermal vias or insulating pads in many designs.

Applications

Television Horizontal Deflection	AC Mains-Fed Audio Amplifier
Use Scenario: Drives flyback transformer primary in CRT TV horizontal output stage with 110–230 VAC direct-line input. IC Role / Device Role / Timing Role: NPN power switch operating in saturated switching mode at ~15.734 kHz, handling peak currents up to 1 A. Use Value: 350 V_CEO withstands retrace voltage spikes; 20 W dissipation accommodates duty-cycle losses without forced cooling.	Use Scenario: Output stage in transformerless Class-B/BTL audio amplifier powering 4–8 Ω speakers from rectified 230 VAC rails. IC Role / Device Role / Timing Role: Medium-power linear amplifier transistor biased in active region, delivering up to 10 W RMS into speaker load. Use Value: h_FE range (30–240) supports stable bias over temperature; TO-225 tab enables direct mounting to chassis for passive thermal management.
Phonograph Power Supply	Radio Tuner Power Regulator
Use Scenario: Series pass element in unregulated linear power supply for vintage turntable motor and preamp circuits. IC Role / Device Role / Timing Role: High-voltage series regulator transistor dissipating up to 15 W while dropping 200–300 VDC input to 12–24 VDC output. Use Value: 375 V_CB rating prevents breakdown during transient overvoltage; R_θJC = 6.25°C/W allows heatsink sizing for steady-state thermal stability.	Use Scenario: Regulated B+ supply generator for AM/FM tuner front-end ICs requiring stable 12–18 VDC from rectified AC line. IC Role / Device Role / Timing Role: Medium-current shunt or series regulator transistor maintaining constant voltage under varying load (10–100 mA). Use Value: Low I_CBO (≤100 nA) minimizes leakage-induced regulation drift; wide h_FE tolerance simplifies feedback loop compensation.

Television Horizontal Deflection

AC Mains-Fed Audio Amplifier

Use Scenario: Drives flyback transformer primary in CRT TV horizontal output stage with 110–230 VAC direct-line input.

IC Role / Device Role / Timing Role: NPN power switch operating in saturated switching mode at ~15.734 kHz, handling peak currents up to 1 A.

Use Value: 350 V_CEO withstands retrace voltage spikes; 20 W dissipation accommodates duty-cycle losses without forced cooling.

Use Scenario: Output stage in transformerless Class-B/BTL audio amplifier powering 4–8 Ω speakers from rectified 230 VAC rails.

IC Role / Device Role / Timing Role: Medium-power linear amplifier transistor biased in active region, delivering up to 10 W RMS into speaker load.

Use Value: h_FE range (30–240) supports stable bias over temperature; TO-225 tab enables direct mounting to chassis for passive thermal management.

Phonograph Power Supply

Radio Tuner Power Regulator

Use Scenario: Series pass element in unregulated linear power supply for vintage turntable motor and preamp circuits.

IC Role / Device Role / Timing Role: High-voltage series regulator transistor dissipating up to 15 W while dropping 200–300 VDC input to 12–24 VDC output.

Use Value: 375 V_CB rating prevents breakdown during transient overvoltage; R_θJC = 6.25°C/W allows heatsink sizing for steady-state thermal stability.

Use Scenario: Regulated B+ supply generator for AM/FM tuner front-end ICs requiring stable 12–18 VDC from rectified AC line.

IC Role / Device Role / Timing Role: Medium-current shunt or series regulator transistor maintaining constant voltage under varying load (10–100 mA).

Use Value: Low I_CBO (≤100 nA) minimizes leakage-induced regulation drift; wide h_FE tolerance simplifies feedback loop compensation.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
MJE13003	Lower V_CEO (400 V vs. 350 V), higher I_C (1.5 A), same TO-225 package but different pinout (emitter-base-collector vs. emitter-collector-base).	Higher peak current capability suits flyback snubber or SMPS primary switching; not drop-in due to pinout mismatch.	Select when higher surge current is needed and board layout allows pin remapping.
BD239C	Same V_CEO (350 V), lower P_D (15 W), identical pinout and package; h_FE min 40 (tighter gain spread).	Better gain consistency for linear amplifiers; reduced power margin limits use in high-duty-cycle deflection stages.	Prefer where tighter h_FE control improves bias stability and 15 W suffices.

Compared with BD159, MJE13003 offers higher voltage headroom and current but requires PCB redesign, while BD239C delivers tighter gain and same pinout at lower power-making it a layout-compatible upgrade only if thermal budget permits.

Availability

BD159 is available at Aetrix Electronics and suitable for television deflection circuits, AC mains-powered audio amplifiers, phonograph power supplies, and radio tuner regulators requiring stable component supply and long-lifecycle availability.

Supply support for BD159 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

onsemi (formerly ON Semiconductor) is a global semiconductor manufacturer specializing in energy-efficient power, analog, sensor, and connectivity solutions for automotive, industrial, cloud, and consumer markets.

The BD159 belongs to onsemi's legacy medium-power bipolar transistor family, engineered specifically for cost-sensitive, high-reliability line-operated consumer electronics where transformerless design, thermal robustness, and long-term manufacturability are critical.

FAQ

What is the maximum collector-emitter voltage rating for BD159?

The BD159 has a maximum collector-emitter sustaining voltage (BV_CEO) of 350 Vdc at I_C = 1.0 mA and I_B = 0. This rating is validated under specified test conditions and defines the upper limit for safe operation in high-voltage switching applications such as horizontal deflection stages. Exceeding this voltage risks avalanche breakdown and permanent damage to the BD159.

Does BD159 have a built-in heatsink connection?

Yes, the BD159 uses a TO-225 package with pins 2 and 4 internally connected to the collector and to the metal tab. This tab serves as both electrical collector terminal and mechanical heatsink interface. When mounted with insulating hardware, the tab must be electrically isolated; when used bare, it becomes part of the collector circuit-requiring careful grounding analysis in the BD159 application layout.

Is BD159 RoHS compliant and what does the "G" suffix indicate?

Yes, BD159G is RoHS compliant and Pb-free. The "G" suffix explicitly denotes conformance to EU Directive 2011/65/EU, indicating lead-free termination plating and compatibility with standard reflow soldering profiles. The BD159G marking also appears as "BD159G" on the device body along with year-week date code, confirming its environmental compliance status per onsemi documentation.

What is the safe operating area (SOA) limitation for BD159 at 100°C case temperature?

At T_C = 100°C, the BD159's power dissipation must be derated to 8.0 W (from 20 W at 25°C), based on its 0.16 W/°C derating coefficient. Its SOA is thermally limited below 100°C and second-breakdown limited at higher voltages/currents. Pulse operation must remain within the single-pulse SOA curves shown in Figure 3 of the BD159 datasheet to avoid catastrophic failure.

Can BD159 replace BD139 in existing designs?

BD159 is not a direct replacement for BD139 due to differences in voltage rating (BD159: 350 V_CEO; BD139: 80 V_CEO) and power dissipation (BD159: 20 W; BD139: 12.5 W). While both use TO-126 packages and share similar pinouts, substituting BD159 into a BD139 design may cause excessive gain instability or unnecessary cost. The BD159 is intended for higher-voltage line-operated applications where BD139 would fail catastrophically.

BD159 Specifications

Product attributes: Attribute value

Manufacturer:: onsemi

Series:: -

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

Packaging:: Bulk

Product Status:: Obsolete

Transistor Type:: NPN

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

Voltage - Collector Emitter Breakdown (Max):: 350 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:: -65°C ~ 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: TO-126

BD159 FAQ

1.How can I place an order for BD159 through Aetrix?

Please submit a Request for Quotation (RFQ) for BD159 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 BD159 reliable?

The price and inventory of BD159 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BD159 is usually 5 days.

3.What payment methods are accepted for BD159?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BD159 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for BD159?

BD159 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your BD159 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 BD159?

For technical support, including BD159 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BD159 requirements.

6.How does Aetrix verify that BD159 is sourced from the original manufacturer or authorized distributors?

All BD159 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 BD159 meets industry standards.

7.What is the process for return or replacement of BD159?

All BD159 units undergo pre-shipment inspection (PSI). If there is an issue with BD159, 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 BD159 part is unused and in its original packaging.

Return procedure for BD159:

1.Submit a request within 90 days.

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

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