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

STMicroelectronics BSS44

Name: BSS44
Brand: STMicroelectronics
SKU: BSS44
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: BSS44

Manufacturer:: STMicroelectronics

Category:: Single Bipolar Transistors

Package:: TO-205AD, TO-39-3 Metal Can

Datasheet:: BSS44.pdf

Description:: TRANS PNP 60V 5A TO-39

Quantity:: RFQ Add To RFQ list

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Inventory:9,676

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Product details

Overview

BSS44 from STMicroelectronics is a silicon epitaxial planar PNP bipolar junction transistor in TO-39 metal package, rated for −60 V V_CEO, −5 A continuous collector current, and 0.87 W power dissipation at T_amb ≤ 25 °C; used in high-current DC switching and linear power regulation circuits such as relay drivers and battery-powered load controls.

For engineers reviewing the BSS44 datasheet, BSS44 pinout, BSS44 application, or BSS44 equivalent, key selection criteria include verified V_CEO(sus) = −60 V, h_FE ≥ 30 at I_C = −0.5 A, V_CE(sat) ≤ −0.4 V at I_C = −5 A/I_B = −0.5 A, thermal resistance R_thj-amb = 200 °C/W, and TO-39 mechanical compatibility with heatsink-mounting requirements.

Technical Context

The BSS44 operates as a medium-power PNP switch with base-controlled current amplification, supporting pulsed operation (300 µs, 1.5% duty cycle) and sustaining voltage capability up to −60 V under open-base conditions. Its f_T of 80 MHz enables moderate-speed switching in analog and digital interface stages.

Designed for ambient-temperature-limited linear and switching applications, it features low V_BE(sat) (−1.1 V typ. at I_C = −2 A), tight V_CE(sat) tolerance (−0.1 V min. at light load), and robust junction temperature rating up to 200 °C - critical for thermally constrained industrial control modules.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	−60 V: Maximum safe collector-emitter blocking voltage with base open; defines upper limit for DC bus voltage in relay or solenoid driver designs.
I_C (cont.)	−5 A: Continuous collector current rating at T_case ≤ 25 °C; supports high-side load switching in 12–24 V systems without forced cooling.
V_CE(sat)	−0.4 V max at I_C = −5 A/I_B = −0.5 A: Low saturation voltage minimizes conduction loss and self-heating during sustained on-state operation.
h_FE	30–70 at I_C = −0.5 to −5 A: Sufficient DC gain for direct microcontroller GPIO drive without external base amplification.
R_thj-amb	200 °C/W: Thermal resistance from junction to ambient; requires heatsinking or airflow for >0.3 W steady-state dissipation.
f_T	80 MHz: Transition frequency confirms usable bandwidth for PWM frequencies up to ~5–10 MHz in non-critical timing paths.

Pinout & Package

TO-39 metal can package with 3-terminal configuration: hermetically sealed, solderable leads, designed for mechanical stability and thermal transfer via case mounting.

Pin/Terminal	Circuit Role	Design Meaning
Emitter (E)	Current source terminal for PNP device	Connected to positive supply rail in high-side switch configurations; must handle full load current and withstand reverse voltage transients.
Base (B)	Control input for minority-carrier injection	Requires negative bias relative to emitter; driven by logic-level or resistor-limited current source to ensure reliable saturation.
Collector (C)	Current sink terminal	Connected to load return path; exposed metal case is electrically connected to collector - mandates isolation from heatsink unless collector is referenced to chassis ground.

Key Features

Feature	Design Value
High V_CEO(sus)	−60 V sustaining voltage ensures stable operation under inductive load turn-off spikes without secondary breakdown.
Low V_CE(sat)	−0.1 V typical at light load enables efficient operation in battery-powered regulators where dropout voltage matters.
Robust thermal rating	Junction temperature limit of 200 °C allows use in sealed enclosures or high-ambient environments like automotive engine bays.
Pulsed switching capability	Validated 300 µs pulse width / 1.5% duty cycle supports intermittent high-current actuation (e.g., fuel injectors, valve coils).

Applications

Relay Driver Circuit

DC Motor Brake Control

Use Scenario: Driving 24 V, 2 A electromagnetic relay coil in industrial PLC output modules.

IC Role / Device Role / Timing Role: High-side PNP switch providing isolated coil energization with fast turn-on/turn-off (t_on = 0.065 µs, t_off = 0.45 µs).

Use Value: −60 V V_CEO clamps flyback voltage; −5 A rating accommodates relay inrush; TO-39 case enables direct PCB-mounted heatsinking.

Use Scenario: Shorting motor terminals during dynamic braking in 12 V brushed DC motor systems.

IC Role / Device Role / Timing Role: Power-stage switch sinking motor back-EMF into ground, activated only during deceleration.

Use Value: −0.4 V V_CE(sat) limits I²R loss at 5 A brake current; 200 °C T_j(max) tolerates brief thermal overload during stall events.

Linear Voltage Regulator Pass Element

High-Voltage Level Shifter

Use Scenario: Series pass transistor in adjustable 5–15 V linear regulator supplying analog sensor circuitry.

IC Role / Device Role / Timing Role: Continuously biased PNP element regulating output by varying V_BE control voltage.

Use Value: h_FE ≥ 40 at I_C = −2 A ensures stable loop gain; R_thj-amb = 200 °C/W informs heatsink sizing for 0.5 W dissipation.

Use Scenario: Translating 3.3 V logic signals to −24 V control lines in industrial I/O isolation barriers.

IC Role / Device Role / Timing Role: Inverting level translator with emitter tied to −24 V rail and base driven by optocoupler output.

Use Value: V_EB(max) = −6 V permits safe base-emitter reverse bias; f_T = 80 MHz supports 1–2 MHz signal edge rates.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
MJD44H11T4	TO-252 DPAK package; higher I_C = −8 A; lower V_CEO = −80 V; R_thj-amb = 62.5 °C/W	Surface-mount compatible; better thermal performance but requires PCB layout change and requalification.	Select when board space is constrained and thermal management via copper pour is preferred over TO-39 heatsinking.
BD140	TO-126 package; same V_CEO = −80 V; I_C = −1.5 A; h_FE = 40–250; R_thj-amb = 100 °C/W	Lower current rating; wider h_FE spread increases base drive design margining effort.	Choose for cost-sensitive, lower-power alternatives where −1.5 A suffices and lead-forming flexibility is needed.

Compared with MJD44H11T4 and BD140, the BSS44 offers optimal balance of legacy through-hole reliability, −5 A capability, and TO-39 mechanical ruggedness for field-serviceable industrial hardware - especially where replacement availability and mechanical interchangeability outweigh surface-mount density gains.

Availability

BSS44 is available at Aetrix Electronics and suitable for relay drivers, DC motor brake circuits, linear regulator pass elements, and high-voltage level shifters requiring stable component supply across long-lifecycle industrial programs.

Supply support for BSS44 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, MCU, and sensor solutions for industrial, automotive, and consumer markets.

The BSS44 belongs to ST's legacy bipolar power transistor product line, engineered specifically for robust, high-reliability discrete switching in harsh-environment control systems where hermetic packaging and proven thermal behavior are mandatory.

FAQ

Is the BSS44 still in active production?

No - STMicroelectronics has marked the BSS44 as obsolete per its official datasheet revision history (document ID BSS44, page 1/4, December 2000). However, Aetrix Electronics maintains legacy inventory and provides controlled-life-cycle sourcing with full traceability and extended warranty for existing designs.

Can the BSS44 be used in avalanche mode?

No - the BSS44 is not rated or characterized for controlled avalanche operation. Its V_CEO(sus) = −60 V reflects sustaining voltage under specified test conditions, not energy-rated avalanche capability. Use only within absolute maximum ratings with appropriate snubbing for inductive loads.

What is the electrical connection between the TO-39 metal case and internal terminals?

The TO-39 metal case is internally connected to the collector terminal. This requires electrical isolation from any heatsink or chassis unless the collector node is intentionally grounded or chassis-referenced in the system design.

Does the BSS44 require a base resistor when driven by a 3.3 V microcontroller GPIO?

Yes - because the BSS44 is PNP, the base must be pulled below emitter potential to conduct. A 1–2.2 kΩ pull-down resistor from base to ground (with GPIO sourcing current to base via series resistor) ensures sufficient I_B ≥ −50 mA for full saturation at I_C = −5 A, per datasheet test condition.

BSS44 Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

Package/Case:: TO-205AD, TO-39-3 Metal Can

Packaging:: Bag

Product Status:: Obsolete

Transistor Type:: PNP

Current - Collector (Ic) (Max):: 5 A

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

Vce Saturation (Max) @ Ib, Ic:: 1V @ 500mA, 5A

Current - Collector Cutoff (Max):: 500nA

DC Current Gain (hFE) (Min) @ Ic, Vce:: 40 @ 2A, 2V

Power - Max:: 870 mW

Frequency - Transition:: 80MHz

Operating Temperature:: 200°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: TO-39

BSS44 FAQ

1.How can I place an order for BSS44 through Aetrix?

Please submit a Request for Quotation (RFQ) for BSS44 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 BSS44 reliable?

The price and inventory of BSS44 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BSS44 is usually 5 days.

3.What payment methods are accepted for BSS44?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BSS44 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for BSS44?

BSS44 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your BSS44 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 BSS44?

For technical support, including BSS44 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BSS44 requirements.

6.How does Aetrix verify that BSS44 is sourced from the original manufacturer or authorized distributors?

All BSS44 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 BSS44 meets industry standards.

7.What is the process for return or replacement of BSS44?

All BSS44 units undergo pre-shipment inspection (PSI). If there is an issue with BSS44, 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 BSS44 part is unused and in its original packaging.

Return procedure for BSS44:

1.Submit a request within 90 days.

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

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