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

onsemi BC517_D27Z

Name: BC517_D27Z
Brand: onsemi
SKU: BC517_D27Z
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: BC517_D27Z

Manufacturer:: onsemi

Category:: Single Bipolar Transistors

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

Datasheet:: BC517_D27Z.pdf

Description:: TRANS NPN DARL 30V 1.2A TO-92-3

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Product details

Overview

BC517_D27Z from ON Semiconductor (formerly Fairchild) is an NPN Darlington transistor optimized for high-current-switching applications, featuring a minimum DC current gain (h_FE) of 30,000 at IC = 20 mA, V_CE = 2.0 V, collector-emitter breakdown voltage (V_CEO) of 30 V, continuous collector current (I_C) up to 1.2 A, and TO-92 package. It is used in relay drivers, lamp drivers, and low-frequency power switching circuits.

For engineers reviewing the BC517_D27Z datasheet, pinout, applications, or equivalent options, key selection considerations include its Darlington configuration for ultra-high gain, saturation voltage (V_CE(sat) = 1 V at I_C = 100 mA/I_B = 0.1 mA), thermal resistance (R_θJA = 200 °C/W), and suitability for discrete logic-level interface with inductive loads.

Technical Context

The BC517_D27Z integrates two cascaded NPN transistors in a monolithic Darlington pair, delivering extremely high current amplification without external bias networks. Its internal structure enables single-base control of high collector currents while maintaining low base drive requirements - critical for microcontroller-driven switching where GPIO current is limited.

It operates as a saturated switch rather than a linear amplifier, with specified V_BE(on) = 1.4 V (IC = 10 mA, V_CE = 5.0 V) and guaranteed V_CE(sat) ≤ 1 V under defined drive conditions. The device is rated for junction temperatures from –55 °C to +150 °C and features a maximum total power dissipation of 625 mW at 25 °C.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	30 V - Maximum safe collector-emitter voltage before breakdown; defines upper limit for driving relays or lamps from 24 V rails.
h_FE	30,000 min - Enables µA-level base current to switch >100 mA collector load; reduces MCU GPIO burden significantly.
V_CE(sat)	1 V max at I_C = 100 mA / I_B = 0.1 mA - Low saturation loss preserves efficiency in battery-powered switching stages.
I_C (cont.)	1.2 A - Supports direct drive of solenoids, small motors, or LED arrays without external heat sinking in intermittent duty.
R_θJA	200 °C/W - Requires careful PCB copper area planning for sustained >500 mA operation; derates 5.0 mW/°C above 25 °C.
T_J Range	–55 °C to +150 °C - Qualified for industrial and automotive under-hood environments where ambient exceeds 85 °C.

Pinout & Package

Package: TO-92 - Standard through-hole plastic package with 3.60 mm ±0.20 mm body width, 4.58 mm ±0.20 mm height, and 1.27 mm lead pitch. Compatible with wave soldering and manual prototyping.

Pin/Terminal	Circuit Role	Design Meaning
1 (Collector)	High-current output node	Connected to load (e.g., relay coil anode); carries full switched current up to 1.2 A.
2 (Base)	Control input	Receives low-current drive signal; 0.1 mA base current suffices to saturate at 100 mA collector load.
3 (Emitter)	Common reference terminal	Typically tied to ground; provides return path for both internal transistors' emitter currents.

Key Features

Feature	Design Value
Ultra-high DC current gain	h_FE ≥ 30,000 ensures <100 µA base drive switches 100 mA loads - ideal for weak-drive MCUs like PIC10F or MSP430.
Darlington architecture	Monolithic dual-NPN integration eliminates external wiring, improves thermal coupling, and guarantees matched transistor characteristics.
Low V_CE(sat)	≤1 V at rated I_C/I_B minimizes conduction loss and self-heating during sustained on-state operation.
Industrial temperature range	–55 °C to +150 °C operation supports deployment in motor control enclosures, HVAC actuators, and outdoor lighting systems.

Applications

Relay Driver Circuit	Lamp & LED Array Control
Use Scenario: Driving 12 V/24 V electromagnetic relays in PLC I/O modules where microcontroller GPIOs supply only 5 mA. IC Role / Device Role: High-gain switching element that translates logic-level signals into full coil current (e.g., 80–150 mA). Use Value: Eliminates need for additional pre-driver stage; enables direct interface between 3.3 V/5 V MCUs and relay coils.	Use Scenario: Controlling incandescent lamps or multi-segment LED arrays in building automation panels. IC Role / Device Role: Low-side switch handling peak currents up to 1.2 A during inrush or dimming transitions. Use Value: Sustains high surge currents without secondary protection; simplifies BOM by replacing discrete driver + MOSFET combos.
Solenoid Actuator Interface	Industrial Sensor Output Stage
Use Scenario: Activating 24 V DC solenoid valves in fluid control systems with pulse-width-modulated (PWM) timing. IC Role / Device Role: PWM-controlled saturated switch managing inductive energy storage and flyback recovery via external diode. Use Value: Maintains stable on-resistance across temperature; avoids gain collapse during repeated actuation cycles.	Use Scenario: Buffering analog sensor outputs (e.g., thermistor-based temp sensors) to drive long cables or multiple downstream inputs. IC Role / Device Role: Emitter-follower configured as unity-gain current booster with high input impedance. Use Value: Prevents signal attenuation over 10+ meter twisted-pair runs; maintains linearity under varying load capacitance.

Relay Driver Circuit

Lamp & LED Array Control

Use Scenario: Driving 12 V/24 V electromagnetic relays in PLC I/O modules where microcontroller GPIOs supply only 5 mA.

IC Role / Device Role: High-gain switching element that translates logic-level signals into full coil current (e.g., 80–150 mA).

Use Value: Eliminates need for additional pre-driver stage; enables direct interface between 3.3 V/5 V MCUs and relay coils.

Use Scenario: Controlling incandescent lamps or multi-segment LED arrays in building automation panels.

IC Role / Device Role: Low-side switch handling peak currents up to 1.2 A during inrush or dimming transitions.

Use Value: Sustains high surge currents without secondary protection; simplifies BOM by replacing discrete driver + MOSFET combos.

Solenoid Actuator Interface

Industrial Sensor Output Stage

Use Scenario: Activating 24 V DC solenoid valves in fluid control systems with pulse-width-modulated (PWM) timing.

IC Role / Device Role: PWM-controlled saturated switch managing inductive energy storage and flyback recovery via external diode.

Use Value: Maintains stable on-resistance across temperature; avoids gain collapse during repeated actuation cycles.

Use Scenario: Buffering analog sensor outputs (e.g., thermistor-based temp sensors) to drive long cables or multiple downstream inputs.

IC Role / Device Role: Emitter-follower configured as unity-gain current booster with high input impedance.

Use Value: Prevents signal attenuation over 10+ meter twisted-pair runs; maintains linearity under varying load capacitance.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
ULN2003A	7-channel Darlington array, built-in clamp diodes, 500 mA per channel, DIP-16 package.	Designed for parallel digital outputs (e.g., stepper motor phases); not a single-device replacement.	Select when driving multiple independent loads from one IC; requires PCB redesign due to different pin count and footprint.
BC516	Same Darlington topology but lower V_CEO = 30 V (same), lower I_C = 100 mA max, h_FE ≥ 20,000.	Intended for lower-power signal switching; insufficient for >500 mA loads.	Choose only for space-constrained designs needing same TO-92 footprint but reduced current capability.

Compared with ULN2003A and BC516, the BC517_D27Z uniquely balances single-transistor simplicity, 1.2 A current capacity, and ultra-high gain - making it optimal for discrete high-current switching where array integration or footprint reduction is unnecessary.

Availability

BC517_D27Z is available at Aetrix Electronics and suitable for relay drivers, solenoid interfaces, lamp control circuits, and industrial sensor output stages requiring stable component supply across extended production lifecycles.

Supply support for BC517_D27Z 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 focused on energy-efficient electronics, delivering power management, analog, sensor, and discrete solutions for automotive, industrial, and cloud infrastructure markets.

The BC517_D27Z belongs to ON Semiconductor's legacy general-purpose bipolar transistor family, engineered specifically for high-gain, medium-current switching in cost-sensitive industrial controls and electro-mechanical interfaces.

FAQ

What is the maximum continuous collector current rating for BC517_D27Z?

The BC517_D27Z is rated for a continuous collector current (I_C) of 1.2 A at T_A = 25 °C. This rating assumes adequate PCB copper area for heat dissipation and derates linearly by 5.0 mW/°C above 25 °C ambient. In practice, sustained operation above 500 mA requires thermal design verification using R_θJA = 200 °C/W.

Does BC517_D27Z include a built-in base-emitter resistor?

No, the BC517_D27Z does not integrate any base-emitter resistors. It is a bare Darlington pair requiring external base current limiting - typically a series resistor between MCU GPIO and pin 2 (Base). This allows precise control of drive strength and avoids unintended turn-on due to leakage.

Can BC517_D27Z be used as a linear amplifier?

The BC517_D27Z is characterized and qualified exclusively for switching applications. Its Darlington structure exhibits high V_BE(on) (1.4 V) and significant V_CE(sat), making it unsuitable for linear amplification. For analog gain stages, discrete small-signal transistors such as BC547 or MMBT3904 are recommended instead of BC517_D27Z.

What is the pin configuration of BC517_D27Z in TO-92 package?

When viewed with flat side facing forward and leads pointing downward, BC517_D27Z follows standard TO-92 pinout: Pin 1 = Collector, Pin 2 = Base, Pin 3 = Emitter. This matches JEDEC TO-92 outline and is consistent across ON Semiconductor's BC5xx Darlington series, including BC517_D27Z.

Is BC517_D27Z RoHS compliant and halogen-free?

Yes, BC517_D27Z is RoHS compliant and halogen-free per ON Semiconductor's product change notification PCN-1407 (2014). The TO-92 molding compound meets IEC 61249-2-21 requirements, and all plating finishes are lead-free. Full compliance documentation is available upon request for BC517_D27Z.

BC517_D27Z Specifications

Product attributes: Attribute value

Manufacturer:: onsemi

Series:: -

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

Packaging:: Tape & Reel (TR)

Product Status:: Obsolete

Transistor Type:: NPN - Darlington

Current - Collector (Ic) (Max):: 1.2 A

Voltage - Collector Emitter Breakdown (Max):: 30 V

Vce Saturation (Max) @ Ib, Ic:: 1V @ 100µA, 100mA

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

DC Current Gain (hFE) (Min) @ Ic, Vce:: 30000 @ 20mA, 2V

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

BC517_D27Z FAQ

1.How can I place an order for BC517_D27Z through Aetrix?

Please submit a Request for Quotation (RFQ) for BC517_D27Z 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 BC517_D27Z reliable?

The price and inventory of BC517_D27Z are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BC517_D27Z is usually 5 days.

3.What payment methods are accepted for BC517_D27Z?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BC517_D27Z transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for BC517_D27Z?

BC517_D27Z orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your BC517_D27Z 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 BC517_D27Z?

For technical support, including BC517_D27Z datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BC517_D27Z requirements.

6.How does Aetrix verify that BC517_D27Z is sourced from the original manufacturer or authorized distributors?

All BC517_D27Z 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 BC517_D27Z meets industry standards.

7.What is the process for return or replacement of BC517_D27Z?

All BC517_D27Z units undergo pre-shipment inspection (PSI). If there is an issue with BC517_D27Z, 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 BC517_D27Z part is unused and in its original packaging.

Return procedure for BC517_D27Z:

1.Submit a request within 90 days.

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

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