onsemi TN6725A

Overview

TN6725A from Fairchild Semiconductor is an NPN Darlington transistor optimized for high-current switching applications up to 1.2 A, featuring h_FE ≥ 15,000 at I_C = 1 A, V_CE = 5 V, and V_CE(sat) ≤ 1.5 V under same conditions-used in relay drivers, lamp controls, and industrial solenoid interfaces.

For engineers reviewing the TN6725A datasheet, pinout, applications, or equivalent options, key selection factors include guaranteed DC current gain at 1 A, low V_BE(sat) (≤2 V), TO-226 package thermal resistance (R_θJA = 125°C/W), and BVCES = 50 V for robust off-state blocking.

Technical Context

The TN6725A implements a monolithic NPN Darlington pair with integrated base-emitter resistor network, enabling high current gain without external bias components. It operates with a maximum junction temperature of 150°C and supports continuous collector currents up to 1.2 A under specified thermal conditions.

Its Darlington architecture delivers h_FE ≥ 40,000 at I_C = 200 mA and ≥15,000 at I_C = 1 A, while maintaining V_CE(sat) ≤ 1.5 V and V_BE(sat) ≤ 2 V-critical for minimizing drive power in low-voltage control circuits.

Key Specifications

Pinout & Package

Package: TO-226 (also known as TO-92), through-hole, 3-lead plastic case with emitter-base-collector pin sequence (E-B-C) when viewed with flat side facing user and leads downward.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MPSA14 and ULN2003A, the TN6725A uniquely supports 1.2 A continuous collector current with guaranteed h_FE ≥ 15,000 at that level-making it the only option among the three for single-device, high-current, low-drive switching in space-constrained designs.

Availability

TN6725A is available at Aetrix Electronics and suitable for industrial control systems, relay interface modules, and solenoid actuation circuits requiring stable component supply and long-term obsolescence management.

Supply support for TN6725A 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

Fairchild Semiconductor was a U.S.-based semiconductor manufacturer specializing in power discrete devices, analog ICs, and optoelectronics before its acquisition by ON Semiconductor in 2016.

The TN6725A belongs to Fairchild's Discrete Power & Signal Technologies family, designed specifically for high-gain, medium-current switching in industrial and automotive control applications where minimal base drive and robust thermal performance are essential.

FAQ

What is the maximum continuous collector current rating for the TN6725A?

The TN6725A has a maximum continuous collector current (I_C) rating of 1.2 A at T_A = 25°C. This rating assumes proper PCB copper area or heatsinking to maintain junction temperature ≤150°C. Derating is required above 25°C ambient-PD decreases by 8 mW/°C, and R_θJA = 125°C/W must be respected in layout design. The TN6725A achieves this while maintaining V_CE(sat) ≤ 1.5 V at 1 A.

Does the TN6725A require an external base resistor?

No, the TN6725A does not require an external base resistor. It integrates a monolithic Darlington structure with built-in base-emitter resistor network, enabling direct connection of the base terminal to a logic-level control signal. This simplifies circuit design and reduces component count compared to discrete transistor pairs. The TN6725A's internal configuration ensures stable biasing across temperature and process variation.

What is the guaranteed DC current gain (h_FE) of the TN6725A at 1 A collector current?

The TN6725A guarantees h_FE ≥ 15,000 at I_C = 1 A, V_CE = 5 V, and T_A = 25°C. This high gain allows microcontroller GPIOs delivering as little as 2 mA base current to fully saturate the device and switch 1 A loads. The TN6725A also specifies h_FE ≥ 25,000 at 500 mA and ≥ 40,000 at 200 mA under identical test conditions.

Can the TN6725A replace the MPSA14 in existing designs?

The TN6725A is not a drop-in replacement for the MPSA14 due to higher current capability (1.2 A vs. 0.5 A), different gain profile, and distinct thermal characteristics. While both are NPN Darlington transistors in TO-92 packages, the TN6725A's higher I_C and h_FE at 1 A may cause unintended stress in circuits originally designed for MPSA14's lower ratings. Replacing MPSA14 with TN6725A requires verification of thermal margin, drive strength, and transient response. The TN6725A is not recommended as a blind substitute.

What is the safe operating voltage range for the TN6725A's collector-emitter junction?

The TN6725A has a guaranteed collector-emitter breakdown voltage (BVCES) of 50 V, meaning it can safely block up to 50 V in the off state with I_C ≤ 1 mA. Its VCBO rating is 60 V and VEBO is 12 V. For reliable operation, applied V_CE should remain ≤ 40 V in production designs to maintain margin against transients and temperature drift. The TN6725A's 50 V BVCES makes it suitable for 24 V industrial systems but not for 48 V nominal rails without external clamping.