onsemi TN6725A_D74Z

Overview

TN6725A_D74Z from Fairchild Semiconductor is an NPN Darlington transistor optimized for high-current switching applications up to 1.2 A, with DC current gain (hFE) of 40,000 at IC = 200 mA and VCE = 5 V, VCE(sat) ≤ 1.5 V at IC = 1 A/IB = 2 mA, and BVCES = 50 V - used in relay drivers, lamp controls, and industrial solenoid interfaces.

For engineers reviewing the TN6725A_D74Z datasheet, pinout, applications, or equivalent options, key selection criteria include guaranteed hFE ≥ 15,000 at 1 A, TO-226 package thermal resistance (RθJA = 125°C/W), VBE(sat) ≤ 2.0 V, and BVEBO = 12 V compliance for base-emitter reverse protection.

Technical Context

The TN6725A_D74Z integrates two cascaded NPN transistors in a monolithic Darlington configuration, delivering ultra-high current gain while maintaining single-package simplicity. It operates with a maximum junction temperature of 150°C and supports continuous collector currents up to 1.2 A under TA = 25°C conditions.

Its saturation behavior is characterized by VCE(sat) = 1.0 V (IC = 200 mA, IB = 2 mA) and 1.5 V (IC = 1 A, IB = 2 mA), and it exhibits low leakage: ICBO ≤ 100 nA at VCB = 40 V and IEBO ≤ 100 nA at VEB = 10 V - enabling stable operation in low-power standby circuits.

Key Specifications

Pinout & Package

Package: TO-226 (also known as TO-92), molded plastic case with 3 leads; standard lead configuration (E-B-C viewed from flat side, leads down).

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_D74Z delivers superior single-device current handling (1.2 A vs. 500 mA), tighter VCE(sat) control at high current, and higher hFE stability across its full operating range - making it optimal for discrete high-gain, high-current switching where board space and thermal management permit TO-226 mounting.

Availability

TN6725A_D74Z is available at Aetrix Electronics and suitable for industrial control systems, relay interface modules, and solenoid driver assemblies requiring stable component supply, long-term lifecycle support, and traceable sourcing from original manufacturer stock.

Supply support for TN6725A_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

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

The TN6725A_D74Z belongs to Fairchild's Discrete Power & Signal Technologies family, engineered for high-gain, medium-power linear and switching applications in industrial and automotive subsystems.

FAQ

What is the maximum continuous collector current rating for TN6725A_D74Z?

The TN6725A_D74Z has a maximum continuous collector current (IC) rating of 1.2 A at TA = 25°C. Derating is required above 25°C per the specified thermal resistance (RθJA = 125°C/W); at 70°C ambient, usable current drops to approximately 800 mA to maintain TJ ≤ 150°C. This rating assumes adequate PCB copper area or optional heatsinking.

Does TN6725A_D74Z include built-in protection features like flyback diodes?

No, the TN6725A_D74Z is a bare Darlington transistor without integrated protection. External components - such as a reverse-biased flyback diode across inductive loads - are mandatory to suppress voltage spikes during turn-off. Its BVCES = 50 V provides limited transient margin but does not replace dedicated clamping.

Is TN6725A_D74Z pin-compatible with MPSA14?

Yes, TN6725A_D74Z uses the same TO-226 (TO-92) package and identical E-B-C pinout as MPSA14, enabling physical board-level replacement. However, due to higher hFE and lower VCE(sat), base resistor values may require adjustment to avoid overdriving or excessive power dissipation in the base region.

What is the typical base-emitter saturation voltage for TN6725A_D74Z?

The TN6725A_D74Z exhibits a typical base-emitter saturation voltage (VBE(sat)) of 2.0 V at IC = 1 A and IB = 2 mA. This reflects the series-connected BE junctions of the Darlington pair and must be accounted for when designing base drive circuits - e.g., a 5 V MCU GPIO requires ≥3 V headroom for reliable turn-on.

Can TN6725A_D74Z be used in linear amplifier configurations?

While the TN6725A_D74Z is primarily intended for switching, it can operate in linear mode within safe operating area (SOA) limits. At VCE = 5 V and IC = 200 mA, hfe ≈ 40,000 supports high-gain amplification, but thermal runaway risk increases above 100 mW dissipation without active bias stabilization or emitter degeneration.