onsemi 2N6427

Overview

2N6427 from Fairchild Semiconductor is an NPN Darlington transistor designed for high-current-gain switching and amplification in low-frequency applications up to 1.2 A collector current, with V_CEO = 40 V, h_FE ≥ 10,000 at I_C = 10 mA, and TO-92 package. It serves as a high-gain interface device in relay drivers, lamp controls, and power supply enable circuits.

For engineers reviewing the 2N6427 datasheet, pinout, applications, or equivalent options, key selection criteria include guaranteed h_FE > 10,000 at low base drive, V_CE(sat) ≤ 1.5 V at I_C = 500 mA, thermal resistance R_θJA = 200 °C/W on FR-4, and TO-92 mechanical compatibility with legacy through-hole layouts.

Technical Context

The 2N6427 implements a monolithic NPN Darlington pair architecture-two cascaded NPN transistors integrated on a single die-to achieve ultra-high DC current gain while maintaining defined saturation characteristics. Its design targets linear and switching operation under continuous DC bias, not RF or high-speed digital use.

It shares process and electrical characterization with the MPSA14 family but is specified for higher I_C (1.2 A vs. 500 mA) and features distinct thermal ratings: P_D = 625 mW at T_A = 25°C, derated at 5.0 mW/°C above ambient, with R_θJC = 83.3 °C/W confirming case-mounted heat dissipation capability.

Key Specifications

Pinout & Package

2N6427 is supplied in the TO-92 through-hole plastic package (JEDEC TO-92 variant), with leads arranged in straight-line configuration and flat side oriented toward emitter. Pin assignment follows standard JEDEC TO-92 outline: Collector (C), Base (B), Emitter (E), left-to-right when viewing flat side with 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 BC639, the 2N6427 delivers superior current gain at high collector currents (h_FE ≥ 14,000 at I_C = 500 mA), enabling simpler drive circuitry for 1 A-class loads while retaining TO-92 compatibility-making it optimal for space-constrained, low-component-count relay and lamp driver designs.

Availability

2N6427 is available at Aetrix Electronics and suitable for relay driver circuits, lamp dimming modules, power supply enable switches, and motor start assist circuits requiring stable component supply across industrial OEM production runs.

Supply support for 2N6427 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 management, analog, and discrete devices before its acquisition by ON Semiconductor in 2016.

The 2N6427 belongs to Fairchild's legacy general-purpose bipolar transistor product line, engineered for high-reliability, cost-sensitive industrial control and power interface applications where robustness and ease of drive are critical.

FAQ

What is the maximum continuous collector current rating for the 2N6427?

The 2N6427 has a maximum continuous collector current rating of 1.2 A at T_A = 25°C. This rating assumes proper PCB thermal management; derating is required above 25°C ambient per the 5.0 mW/°C specification. At elevated temperatures or with limited copper area, sustained operation above 500 mA may require verification of junction temperature using R_θJA = 200 °C/W.

Does the 2N6427 have a documented pinout compatible with standard TO-92 footprints?

Yes, the 2N6427 uses the standard JEDEC TO-92 package with Collector-Base-Emitter (C-B-E) pin order when viewed from the flat side with leads pointing downward. This matches the pinout of MPSA14 and other common TO-92 NPN transistors, enabling direct PCB footprint reuse without layout changes.

What is the minimum DC current gain (h_FE) of the 2N6427 at 10 mA collector current?

The minimum DC current gain (h_FE) of the 2N6427 is 10,000 at I_C = 10 mA and V_CE = 5.0 V. This value is guaranteed per the datasheet's "Electrical Characteristics" table and reflects the Darlington configuration's ability to amplify weak control signals into substantial load currents.

Can the 2N6427 be used in linear (analog) amplification applications?

The 2N6427 is characterized for switching and moderate-frequency linear operation, with specified V_BE(on) = 1.75 V and V_BE(sat) = 2.0 V. While usable in Class-A amplifier stages, its Darlington structure introduces higher base-emitter voltage and lower bandwidth than single transistors; it is optimized for switching rather than high-fidelity analog gain.

Is the 2N6427 RoHS compliant and lead-free?

The original 2N6427 datasheet predates mandatory RoHS implementation and does not specify lead-free construction. Units currently distributed by Aetrix Electronics comply with applicable environmental regulations including RoHS 2011/65/EU and REACH; full compliance documentation is available upon request for specific lot numbers.