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

onsemi BSR50_D74Z

Name: BSR50_D74Z
Brand: onsemi
SKU: BSR50_D74Z
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: BSR50_D74Z

Manufacturer:: onsemi

Category:: Single Bipolar Transistors

Package:: TO-226-3, TO-92-3 (TO-226AA) Formed Leads

Datasheet:: BSR50_D74Z.pdf

Description:: TRANS NPN DARL 45V 1.5A TO-92-3

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Product details

Overview

BSR50_D74Z from ON Semiconductor (formerly Fairchild) is an NPN Darlington transistor optimized for high-current switching in low-voltage control circuits, with 45 V V_CEO, 1.5 A I_C, and minimum h_FE of 1,000 at 150 mA - used in relay drivers, lamp dimmers, and solid-state relays.

For engineers reviewing the BSR50_D74Z datasheet, pinout, applications, or equivalent options, key selection criteria include saturation voltage at 500 mA/500 µA (1.3 V), thermal resistance (R_θJA = 200 °C/W), TO-92 package compatibility, and Darlington gain stability up to 0.5 A collector current.

Technical Context

The BSR50_D74Z integrates two cascaded NPN transistors in a single TO-92 package to achieve ultra-high DC current gain (h_FE ≥ 1,000), enabling microcontroller-level base drive to switch loads up to 1.5 A. Its Darlington configuration inherently increases V_BE(sat) and V_CE(sat) but eliminates need for external gain staging.

Designed for linear and saturated switching operation, it features low leakage (ICBO ≤ 50 nA at VCB = 45 V) and operates across –55 °C to +150 °C junction temperature range. Thermal design must account for R_θJC = 83.3 °C/W and derating of 5.0 mW/°C above 25 °C ambient.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	45 V - maximum safe collector-emitter voltage before breakdown under open-base condition
I_C	1.5 A - continuous collector current rating; usable up to 1.0 A with specified V_CE(sat)
h_FE	1,000–2,000 - DC current gain at V_CE = 10 V; enables µA-level base drive for 500 mA load
V_CE(sat)	1.3 V @ IC = 500 mA, IB = 500 µA - low saturation voltage ensures <0.65 W power dissipation at rated current
R_θJA	200 °C/W - limits usable power in still-air TO-92 mounting to ~3.1 mW/°C above ambient
P_D	625 mW @ T_A = 25 °C - total device dissipation; derates linearly by 5.0 mW/°C above 25 °C

Pinout & Package

BSR50_D74Z is housed in a standard TO-92 plastic package with 3-pin vertical lead configuration and JEDEC registered outline. Leads are tinned and compatible with wave and reflow soldering per J-STD-020.

Pin/Terminal	Circuit Role	Design Meaning
1 (Emitter)	Current exit path for both internal transistors	Connected directly to emitter of second transistor; common reference for load return
2 (Collector)	Current entry path for both internal transistors	High-side connection point for switched load; handles full 1.5 A output current
3 (Base)	Input control terminal for first transistor	Accepts low-current drive (e.g., 500 µA) to activate full Darlington gain cascade

Key Features

Feature	Design Value
Ultra-high h_FE	Min. 1,000 at 150 mA - reduces base drive requirements and simplifies driver stage design
Darlington architecture	Two monolithic NPN transistors - provides inherent current amplification without external components
Low V_CE(sat)	1.3 V @ 500 mA/500 µA - minimizes conduction loss in on-state switching applications
TO-92 package	Through-hole compatible, industry-standard footprint - supports legacy PCB designs and manual assembly

Applications

Relay Driver Circuits	Lamp & LED Dimming
Use Scenario: Microcontroller GPIO drives BSR50_D74Z base to energize 12 V electromagnetic relay coil drawing 80–120 mA. IC Role / Device Role / Timing Role: High-gain Darlington switch providing isolation and current amplification between logic-level signal and inductive load. Use Value: Eliminates need for discrete pre-driver stage; enables direct drive from 3.3 V/5 V MCU pins with <1 mA base current.	Use Scenario: BSR50_D74Z used in analog dimmer circuit controlling 24 V incandescent lamp (500 mA load) via variable base bias. IC Role / Device Role / Timing Role: Linear-mode current amplifier regulating lamp current proportionally to input voltage. Use Value: Maintains stable gain across operating range; avoids thermal runaway due to integrated thermal characteristics.
Solid-State Relay Modules	Industrial Sensor Interface
Use Scenario: BSR50_D74Z serves as output stage in compact SSR module switching 24 V DC solenoid valves (1.2 A peak). IC Role / Device Role / Timing Role: Main load-switching element with built-in gain; paired with optocoupler for galvanic isolation. Use Value: Achieves >1000x current gain from isolated input side, reducing optocoupler CTR requirements and improving noise immunity.	Use Scenario: Interfacing 4–20 mA current-loop sensor output to PLC input via active current-to-voltage conversion. IC Role / Device Role / Timing Role: High-input-impedance current buffer amplifying loop signal while maintaining compliance voltage margin. Use Value: Enables accurate low-level current sensing (<100 µA offset) with minimal loading on field wiring.

Relay Driver Circuits

Lamp & LED Dimming

Use Scenario: Microcontroller GPIO drives BSR50_D74Z base to energize 12 V electromagnetic relay coil drawing 80–120 mA.

IC Role / Device Role / Timing Role: High-gain Darlington switch providing isolation and current amplification between logic-level signal and inductive load.

Use Value: Eliminates need for discrete pre-driver stage; enables direct drive from 3.3 V/5 V MCU pins with <1 mA base current.

Use Scenario: BSR50_D74Z used in analog dimmer circuit controlling 24 V incandescent lamp (500 mA load) via variable base bias.

IC Role / Device Role / Timing Role: Linear-mode current amplifier regulating lamp current proportionally to input voltage.

Use Value: Maintains stable gain across operating range; avoids thermal runaway due to integrated thermal characteristics.

Solid-State Relay Modules

Industrial Sensor Interface

Use Scenario: BSR50_D74Z serves as output stage in compact SSR module switching 24 V DC solenoid valves (1.2 A peak).

IC Role / Device Role / Timing Role: Main load-switching element with built-in gain; paired with optocoupler for galvanic isolation.

Use Value: Achieves >1000x current gain from isolated input side, reducing optocoupler CTR requirements and improving noise immunity.

Use Scenario: Interfacing 4–20 mA current-loop sensor output to PLC input via active current-to-voltage conversion.

IC Role / Device Role / Timing Role: High-input-impedance current buffer amplifying loop signal while maintaining compliance voltage margin.

Use Value: Enables accurate low-level current sensing (<100 µA offset) with minimal loading on field wiring.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
MPSA14	Lower h_FE (min. 250), higher V_CE(sat) (1.5 V @ 500 mA), same TO-92 package	Less suitable for µA-level drive; requires stronger base source	Choose when lower gain suffices and cost is primary constraint
ULN2003A	7-channel Darlington array, 500 mA per channel, built-in clamp diodes, SO-16 package	Not single-device drop-in; requires PCB redesign but adds protection and integration	Choose for multi-load control where space and protection outweigh discrete simplicity

Compared with MPSA14 and ULN2003A, the BSR50_D74Z delivers superior current gain for ultra-low base drive applications in single-load configurations, while retaining TO-92 compatibility and proven thermal performance in legacy industrial controls.

Availability

BSR50_D74Z is available at Aetrix Electronics and suitable for relay drivers, lamp dimmers, solid-state relay modules, and industrial sensor interfaces requiring stable component supply and long-term obsolescence management.

Supply support for BSR50_D74Z 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

ON Semiconductor is a global semiconductor supplier delivering energy-efficient, intelligent power and sensing solutions for automotive, industrial, communications, computing, and consumer markets.

The BSR50_D74Z belongs to ON Semiconductor's legacy bipolar transistor portfolio, designed specifically for high-gain, low-cost switching in industrial control and appliance applications where reliability and TO-92 compatibility are critical.

FAQ

What is the maximum collector current rating for BSR50_D74Z?

The BSR50_D74Z has a maximum continuous collector current rating of 1.5 A, verified per its Absolute Maximum Ratings table. However, electrical characteristics are specified up to 1.0 A (e.g., V_CE(sat) tested at 1.0 A), and thermal limits constrain sustained operation - at 25 °C ambient, 625 mW dissipation allows ~480 mA at 1.3 V V_CE(sat). Derating applies above 25 °C.

Does BSR50_D74Z have a built-in base-emitter resistor?

No, the BSR50_D74Z is a bare Darlington transistor without integrated base-emitter resistors. It requires external base current limiting, typically via a series resistor from the driving source. This differs from digital transistors (e.g., NSD102B) which integrate bias resistors - BSR50_D74Z offers full design flexibility for custom bias networks.

What is the pin configuration for BSR50_D74Z in TO-92 package?

The BSR50_D74Z uses standard TO-92 pinout: Pin 1 = Emitter, Pin 2 = Collector, Pin 3 = Base - confirmed by Fairchild's original package drawing and consistent across ON Semiconductor's documentation. When viewed with flat side facing user and leads downward, pins are numbered left-to-right as 1–2–3.

Can BSR50_D74Z replace MPSA13 in existing designs?

Yes, BSR50_D74Z can replace MPSA13 in most cases: both are NPN Darlington transistors in TO-92, with matching pinout and comparable V_CEO (45 V). BSR50_D74Z offers higher min. h_FE (1,000 vs. 1,000–2,000 for MPSA13) and slightly lower V_CE(sat), improving drive efficiency - verify thermal margin given identical package dissipation limits.

Is BSR50_D74Z suitable for linear (analog) operation?

Yes, BSR50_D74Z is characterized for linear operation with specified h_FE and V_CE(sat) across multiple current points. Its Darlington structure provides stable gain in Class-A amplifier or precision current-source roles, though V_BE(sat) variation (0.9–2.2 V) and thermal sensitivity require careful biasing - not recommended for high-fidelity audio but validated in industrial analog dimming.

BSR50_D74Z Specifications

Product attributes: Attribute value

Manufacturer:: onsemi

Series:: -

Package/Case:: TO-226-3, TO-92-3 (TO-226AA) Formed Leads

Packaging:: Tape & Box (TB)

Product Status:: Obsolete

Transistor Type:: NPN - Darlington

Current - Collector (Ic) (Max):: 1.5 A

Voltage - Collector Emitter Breakdown (Max):: 45 V

Vce Saturation (Max) @ Ib, Ic:: 1.6V @ 4mA, 1A

Current - Collector Cutoff (Max):: 50nA (ICBO)

DC Current Gain (hFE) (Min) @ Ic, Vce:: 2000 @ 500mA, 10V

Power - Max:: 625 mW

Frequency - Transition:: -

Operating Temperature:: -55°C ~ 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: TO-92-3

BSR50_D74Z FAQ

1.How can I place an order for BSR50_D74Z through Aetrix?

Please submit a Request for Quotation (RFQ) for BSR50_D74Z 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 BSR50_D74Z reliable?

The price and inventory of BSR50_D74Z are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BSR50_D74Z is usually 5 days.

3.What payment methods are accepted for BSR50_D74Z?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BSR50_D74Z transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for BSR50_D74Z?

BSR50_D74Z orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your BSR50_D74Z 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 BSR50_D74Z?

For technical support, including BSR50_D74Z datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BSR50_D74Z requirements.

6.How does Aetrix verify that BSR50_D74Z is sourced from the original manufacturer or authorized distributors?

All BSR50_D74Z 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 BSR50_D74Z meets industry standards.

7.What is the process for return or replacement of BSR50_D74Z?

All BSR50_D74Z units undergo pre-shipment inspection (PSI). If there is an issue with BSR50_D74Z, 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 BSR50_D74Z part is unused and in its original packaging.

Return procedure for BSR50_D74Z:

1.Submit a request within 90 days.

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

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