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

STMicroelectronics BD708

Name: BD708
Brand: STMicroelectronics
SKU: BD708
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: BD708

Manufacturer:: STMicroelectronics

Category:: Single Bipolar Transistors

Package:: TO-220-3

Datasheet:: BD708.pdf

Description:: TRANS PNP 60V 12A TO-220

Quantity:: RFQ Add To RFQ list

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Inventory:7,654

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Product details

Overview

BD708 from STMicroelectronics is a complementary PNP silicon power transistor in TO-220 plastic package, designed for linear and switching applications alongside its NPN counterpart BD707. It delivers 12 A collector current, 60 V collector-emitter sustaining voltage (VCEO(sus)), and 75 W total power dissipation at Tc ≤ 25 °C, used in industrial power supplies and motor control stages.

For engineers reviewing the BD708 datasheet, BD708 pinout, BD708 application, or BD708 equivalent, key selection factors include its complementary pairing with BD707, negative-polarity voltage/current ratings, DC current gain (hFE = 40–120 at IC = 0.5–4 A), thermal resistance (Rthj-case = 1.67 °C/W), and safe operating area (SOA) compliance for linear-mode operation.

Technical Context

The BD708 operates as a high-current PNP bipolar junction transistor with epitaxial-base construction optimized for both linear amplification and hard-switching duty. Its VCEO(sus) = 60 V and IC = 12 A support robust operation in Class-AB audio output stages and DC-DC converter active clamping circuits.

Designed for complementary symmetry with BD707, it shares identical TO-220 mechanical footprint and thermal interface, enabling matched thermal tracking and simplified heatsink mounting. All voltage and current ratings are negative per PNP convention, and SOA curves are validated for pulsed and DC conditions up to 150 °C junction temperature.

Key Specifications

Parameter	Value and Actual Design Meaning
Collector-Emitter Sustaining Voltage	VCEO(sus) = −60 V at IC = 100 mA - defines maximum blocking capability under open-base switching conditions
Collector Current	IC = −12 A continuous - supports high-power load driving without forced cooling below 25 °C case temperature
Power Dissipation	Ptot = 75 W at Tc ≤ 25 °C - enables high-efficiency linear regulation when mounted on ≥10 cm² aluminum heatsink
DC Current Gain	hFE = 40–120 at IC = −0.5 A to −4 A - ensures stable biasing across wide load current range in emitter-follower configurations
Junction-to-Case Thermal Resistance	Rthj-case = 1.67 °C/W - allows direct thermal coupling to heatsink with minimal temperature rise per watt dissipated
Transition Frequency	fT = 3 MHz at IC = −300 mA - supports audio-frequency amplification and moderate-speed switching up to ~100 kHz

Pinout & Package

BD708 uses JEDEC-standard TO-220 plastic package with vertical lead orientation and insulated tab. The collector is internally connected to the metal tab for direct heatsink mounting; emitter and base are on leads 1 and 2 respectively.

Pin/Terminal	Circuit Role	Design Meaning
Tab (Collector)	Main current sink terminal	Electrically and thermally coupled to heatsink; requires insulating washer if mounting to grounded chassis
Lead 1 (Emitter)	Current source terminal	Connects to positive rail in high-side switch or output node in PNP emitter-follower stage
Lead 2 (Base)	Control input	Receives negative drive current; base resistor must limit IB to ≤ −5 A peak per absolute max rating

Key Features

Feature	Design Value
Complementary Pairing	Matched electrical characteristics with BD707 (NPN) for push-pull amplifier symmetry and thermal tracking
High Safe Operating Area	Validated DC and pulsed SOA up to 150 °C junction temperature - supports linear-mode operation without secondary breakdown
Epitaxial Base Construction	Enables tight hFE distribution and low leakage (ICEO ≤ 100 µA at VCE = 30 V) across production lots
Negative-Polarity Ratings	All voltage/current limits explicitly defined as negative values - eliminates sign ambiguity in circuit simulation and layout

Applications

Industrial Power Supply

Audio Output Stage

Use Scenario: Regulated ±15 V dual-rail supply for PLC I/O modules requiring >5 A sustained output current.

IC Role / Device Role / Timing Role: PNP pass transistor in series-regulator topology, sinking current from unregulated rail to load.

Use Value: −60 V VCEO(sus) and −12 A IC enable single-device regulation at 24 V input-to-output differential with margin.

Use Scenario: Complementary Class-AB output stage in 50 W professional audio amplifier.

IC Role / Device Role / Timing Role: High-current PNP emitter-follower delivering negative half-cycle current to 4 Ω speaker load.

Use Value: Matched hFE and SOA with BD707 ensure symmetrical distortion profile and thermal stability during extended full-power operation.

Motor Drive H-Bridge

DC-DC Converter Clamping

Use Scenario: High-side switch in 24 V brushed DC motor driver handling 10 A stall current.

IC Role / Device Role / Timing Role: PNP switch controlling motor voltage rail; driven by NPN level-shifter and current-limited base resistor.

Use Value: −75 W power rating and −1.67 °C/W Rthj-case allow operation at 85 °C ambient without derating when heatsinked.

Use Scenario: Active clamp transistor in flyback converter snubber network limiting voltage overshoot during MOSFET turn-off.

IC Role / Device Role / Timing Role: Fast-saturating PNP clamp activated by transformer auxiliary winding feedback pulse.

Use Value: −1 V VCE(sat) at −4 A IB = −0.4 A ensures low conduction loss and precise voltage clamping at 100 kHz switching frequency.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
MJD708	TO-252 (DPAK) surface-mount package; same VCEO(sus) = −60 V, IC = −10 A, hFE = 40–120	Not suitable for through-hole prototyping or high-power heatsinking without thermal pad vias	Select for space-constrained PCBs where automated assembly and lower profile are prioritized over raw power density
BD712	Higher VCEO(sus) = −100 V, same TO-220 package and hFE range; Ptot = 75 W unchanged	Used where higher bus voltage tolerance is required, e.g., 48 V industrial systems	Select when system input voltage exceeds 60 V or transient immunity above 80 V is mandated

Compared with BD708, MJD708 trades package form factor and thermal performance for SMT compatibility, while BD712 extends voltage capability without altering footprint or gain behavior-enabling drop-in replacement only where voltage headroom is the limiting factor.

Availability

BD708 is available at Aetrix Electronics and suitable for industrial power supplies, audio amplifiers, motor drives, and DC-DC converter clamping circuits requiring stable component supply and long-term obsolescence management.

Supply support for BD708 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 devices for automotive, industrial, and consumer markets.

The BD708 belongs to ST's legacy power bipolar transistor family targeting high-reliability linear and switching power applications, emphasizing rugged SOA, thermal stability, and complementary pairing for analog power stages.

FAQ

Is BD708 pin-compatible with BD707?

No - BD708 (PNP) and BD707 (NPN) share identical TO-220 pinout (Emitter-Base-Collector on leads 1-2-tab), but polarity reversal means external circuit connections must be inverted. Both use collector-connected tab, so heatsink isolation requirements remain identical.

What is the maximum safe continuous collector current at 85 °C case temperature?

At Tc = 85 °C, BD708's power dissipation must be derated linearly from 75 W at 25 °C using Rthj-case = 1.67 °C/W. Maximum allowable Ptot = 75 × (1 − (85−25)/125) = 45 W. With VCE(sat) ≈ −1 V, max continuous IC ≈ −45 A - but absolute max IC remains −12 A, so practical limit is −12 A with adequate heatsinking.

Can BD708 be used in avalanche mode?

No - BD708 is not rated for controlled avalanche operation. Its VCEO(sus) = −60 V is specified under open-base conditions, but no energy-rated avalanche SOA or ruggedness data is provided. Use only within published SOA boundaries; avoid intentional avalanche stress.

Does BD708 require a base-emitter resistor when used as a switch?

Yes - a base-emitter resistor (typically 1–10 kΩ) is recommended to prevent spurious turn-on from leakage or noise, especially in high-temperature or high-humidity environments. This ensures reliable cutoff when base drive is removed, given its relatively high ICEO (≤100 µA).

BD708 Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

Package/Case:: TO-220-3

Packaging:: Tube

Product Status:: Obsolete

Transistor Type:: PNP

Current - Collector (Ic) (Max):: 12 A

Voltage - Collector Emitter Breakdown (Max):: 60 V

Vce Saturation (Max) @ Ib, Ic:: 1V @ 400mA, 4A

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

DC Current Gain (hFE) (Min) @ Ic, Vce:: 15 @ 4A, 4V

Power - Max:: 75 W

Frequency - Transition:: 3MHz

Operating Temperature:: 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: TO-220

BD708 FAQ

1.How can I place an order for BD708 through Aetrix?

Please submit a Request for Quotation (RFQ) for BD708 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 BD708 reliable?

The price and inventory of BD708 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BD708 is usually 5 days.

3.What payment methods are accepted for BD708?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BD708 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for BD708?

BD708 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your BD708 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 BD708?

For technical support, including BD708 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BD708 requirements.

6.How does Aetrix verify that BD708 is sourced from the original manufacturer or authorized distributors?

All BD708 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 BD708 meets industry standards.

7.What is the process for return or replacement of BD708?

All BD708 units undergo pre-shipment inspection (PSI). If there is an issue with BD708, 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 BD708 part is unused and in its original packaging.

Return procedure for BD708:

1.Submit a request within 90 days.

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

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