onsemi BC517_D75Z

Overview

BC517_D75Z 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 rating of 1.2 A, and TO-92 package. It is used in low-speed relay drivers, lamp drivers, and logic-level interface circuits where high input impedance and high current amplification are required.

For engineers reviewing the BC517_D75Z datasheet, pinout, applications, or equivalent options, key selection considerations include its Darlington configuration enabling single-stage high-gain switching, saturation voltage (V_CE(sat) = 1.0 V at I_C = 100 mA / I_B = 0.1 mA), thermal resistance (R_θJA = 200 °C/W), and compatibility with 5 V TTL/CMOS logic drive levels.

Technical Context

The BC517_D75Z integrates two cascaded NPN transistors in a monolithic Darlington pair, delivering ultra-high current gain without external biasing components. Its internal structure eliminates the need for an external base resistor, and it operates with a typical base-emitter on voltage (V_BE(on)) of 1.4 V at I_C = 10 mA, ensuring reliable turn-on from standard logic outputs.

Designed for linear and switching operation up to 1.0 A DC load current, the device features a maximum junction temperature of 150°C and thermal derating of 5.0 mW/°C above 25°C ambient. Its 30 V V_CEO rating supports use in 24 V industrial control rails with margin, while the 100 nA collector cutoff current (I_CBO) ensures low leakage in standby states.

Key Specifications

Pinout & Package

Package: TO-92 - Standard through-hole plastic package with 3.60 mm lead spacing, 14.47 mm body length, and 1.02 mm lead diameter; compatible with wave soldering and manual prototyping.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BC517_D75Z, the base BC517 offers identical performance with less granular traceability, while MPSA14 provides acceptable Darlington functionality at reduced gain-making BC517_D75Z optimal for designs demanding guaranteed minimum h_FE and full compliance documentation.

Availability

BC517_D75Z is available at Aetrix Electronics and suitable for relay driver circuits, lamp control systems, logic-level interface modules, and low-speed motor control applications requiring stable component supply and long-term industrial availability.

Supply support for BC517_D75Z 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, cloud, medical, and IoT applications.

The BC517_D75Z belongs to ON Semiconductor's legacy bipolar transistor portfolio, designed specifically for high-gain, low-frequency switching in cost-sensitive industrial and appliance control systems.

FAQ

What is the maximum continuous collector current rating for BC517_D75Z?

The BC517_D75Z has a maximum continuous collector current (I_C) rating of 1.2 A at T_A = 25°C. This rating assumes adequate PCB copper area for thermal dissipation; derating applies at higher ambient temperatures (5.0 mW/°C above 25°C). In practice, sustained 1 A operation requires thermal design attention due to its R_θJA of 200 °C/W. The BC517_D75Z datasheet confirms this value under Absolute Maximum Ratings.

Does BC517_D75Z require an external base resistor when driven by a microcontroller GPIO?

No, BC517_D75Z does not require an external base resistor when driven by a 5 V microcontroller GPIO. Its Darlington configuration provides sufficient input impedance and gain (h_FE ≥ 30,000) to achieve full saturation with ~100 µA base current. The BC517_D75Z base-emitter on voltage is 1.4 V, allowing direct connection to 5 V logic with current limiting only needed if source drive strength exceeds safe I_B limits.

What is the collector-emitter saturation voltage (V_CE(sat)) of BC517_D75Z under typical operating conditions?

The BC517_D75Z exhibits a typical collector-emitter saturation voltage (V_CE(sat)) of 1.0 V when I_C = 100 mA and I_B = 0.1 mA, as specified in its Electrical Characteristics table. This low saturation voltage minimizes conduction losses in switching applications such as relay or lamp drivers. At higher currents (e.g., I_C = 500 mA), V_CE(sat) rises to approximately 1.5 V, consistent with Darlington behavior and confirmed in the BC517_D75Z datasheet.

Is BC517_D75Z pin-compatible with BC547 or other general-purpose NPN transistors?

No, BC517_D75Z is not pin-compatible with BC547 or other standard NPN transistors. While both use TO-92 packages, BC517_D75Z is a Darlington device with base-collector-emitter pinout (1=C, 2=B, 3=E), whereas BC547 follows emitter-base-collector (1=E, 2=B, 3=C). Swapping them will cause circuit failure. The BC517_D75Z pinout is identical to BC516/BC518 and must be verified against the official BC517_D75Z mechanical drawing before layout.

What is the operating junction temperature range for BC517_D75Z?

The BC517_D75Z supports an operating junction temperature range of –55°C to +150°C, as defined in its Absolute Maximum Ratings. This wide range allows deployment in harsh industrial environments, including automotive under-hood locations and factory automation equipment. Thermal design must ensure that actual junction temperature stays within this limit-achievable via PCB copper area, airflow, or derating per the BC517_D75Z thermal resistance values (R_θJA = 200 °C/W, R_θJC = 83.3 °C/W).