onsemi BD1406S

Overview

BD1406S from Fairchild Semiconductor is a PNP epitaxial silicon transistor designed for medium-power linear amplification and switching applications, with V_CEO = −80 V, I_C = −1.5 A, P_C = 12.5 W at T_C = 25°C, h_FE = 100–250 (at I_C = −150 mA), and TO-126 package. It serves as the complementary PNP counterpart to the NPN BD139 in audio output stages and power control circuits.

For engineers reviewing the BD1406S datasheet, pinout, applications, or equivalent options, key selection considerations include its −80 V V_CEO rating, −1.5 A DC collector current capability, safe operating area under pulsed conditions, thermal derating behavior, and verified compatibility with BD139-based push-pull amplifier designs.

Technical Context

This PNP bipolar junction transistor operates with fixed-base biasing or emitter-follower configurations in Class AB audio output stages and DC motor drive circuits. Its h_FE classification (h_FE3: 100–250) ensures stable current gain across mid-range collector currents (−150 mA), while V_CE(sat) ≤ −0.5 V at I_C = −500 mA / I_B = −50 mA supports low-loss saturation switching.

The device's thermal design relies on case-mounted heatsinking due to its 12.5 W dissipation limit at T_C = 25°C and steep 0.1 W/°C derating above 25°C. Its −5 V V_EB0 rating constrains base-emitter reverse bias in bridge or level-shifted driver topologies.

Key Specifications

Pinout & Package

BD1406S is housed in a TO-126 plastic package with integral metal tab for heatsink mounting. Pin 1 is Emitter, Pin 2 is Collector (connected to tab), Pin 3 is Base - confirmed by Fairchild Rev. A datasheet diagram and dimensioning.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar PNP medium-power transistor applications.

Compared with BD1406S, MJD127 offers higher voltage and current in SMT form but demands layout change, while BD175 retains TO-126 compatibility at reduced voltage margin - neither is drop-in, but both serve adjacent design constraints in industrial power control.

Availability

BD1406S is available at Aetrix Electronics and suitable for audio amplifier output stages, DC motor directional control, linear voltage regulator pass elements, and relay drivers requiring stable component supply and long-term industrial availability.

Supply support for BD1406S 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 designer and manufacturer of analog and discrete semiconductors, acquired by ON Semiconductor in 2016; known for rugged, industry-standard bipolar transistors and power MOSFETs.

The BD1406S belongs to Fairchild's BD136/138/140 family of medium-power PNP transistors engineered specifically for complementary audio output stages, industrial switching, and linear regulation where proven reliability and wide SOA are critical.

FAQ

What is the maximum continuous collector current rating for BD1406S?

The BD1406S has a maximum continuous collector current (I_C) rating of −1.5 A at T_C = 25°C. This rating assumes proper heatsinking; actual usable current decreases with rising case temperature per the 0.1 W/°C derating curve. At T_C = 75°C, the effective I_C limit drops to approximately −1.0 A to maintain safe junction temperature. The BD1406S must not exceed this limit in sustained operation without thermal overload.

Is BD1406S pin-compatible with BD139?

No, BD1406S is not pin-compatible with BD139 - it is complementary in function but opposite polarity. BD1406S is PNP (Emitter–Collector–Base = Pin 1–2–3), while BD139 is NPN (Collector–Emitter–Base = Pin 1–2–3). Their pinouts are mirrored: BD1406S Pin 1 = Emitter, BD139 Pin 1 = Collector. Using them interchangeably without circuit revision will cause immediate failure. The BD1406S pairs with BD139 in push-pull layouts but occupies the opposite side of the schematic.

What is the typical V_CE(sat) of BD1406S under standard test conditions?

The BD1406S exhibits a typical V_CE(sat) of −0.5 V when tested at I_C = −500 mA and I_B = −50 mA (10:1 overdrive ratio), per Fairchild's Rev. A datasheet. This value reflects low-saturation conduction loss ideal for switching applications such as lamp dimming or solenoid actuation. Actual V_CE(sat) may rise slightly at higher temperatures or lower I_B/I_C ratios; the BD1406S datasheet specifies −0.5 V as the maximum guaranteed value under those exact conditions.

Can BD1406S be used in surface-mount designs?

No, BD1406S is exclusively offered in the through-hole TO-126 package and is not available in any surface-mount variant. Its metal tab (Collector) is designed for mechanical screw-mount heatsinking, and the leadframe geometry does not support reflow or wave soldering. For SMT alternatives, consider MJD127 (TO-252) or NSS12201CF8 (SOT-89), though neither matches BD1406S's −80 V rating or SOA. BD1406S requires through-hole PCB layout and manual or selective soldering.

What is the safe operating area (SOA) limitation for BD1406S in DC operation?

The BD1406S DC safe operating area is bounded by I_C ≤ −1.5 A, V_CE ≤ −80 V, and P_C ≤ 12.5 W at T_C = 25°C - with strict derating above that temperature. Per Figure 4 in the Fairchild datasheet, the DC boundary follows a hyperbolic curve: at V_CE = −40 V, max I_C ≈ −1.2 A; at V_CE = −20 V, max I_C ≈ −1.5 A. Exceeding this envelope risks secondary breakdown. The BD1406S must be operated within this validated SOA to ensure long-term reliability in linear applications.