onsemi BD436S

Overview

BD436S from Fairchild Semiconductor is a PNP epitaxial silicon transistor designed for medium-power linear amplification and switching applications, with −32 V collector-emitter sustaining voltage (V_CEO(sus)), −4 A continuous collector current (I_C), 36 W collector dissipation at T_C = 25°C, and DC current gain (h_FE) of 40–140 at I_C = −10 mA to −2 A. It serves as the complement to BD435 in audio output stages and power control circuits.

For engineers reviewing the BD436S datasheet, pinout, applications, or equivalent options, key selection considerations include its TO-126 package thermal performance, −32 V breakdown rating, saturation voltage under high-current switching (V_CE(sat) ≤ −0.6 V at I_C = −2 A, I_B = −0.2 A), and verified use in complementary push-pull amplifier outputs.

Technical Context

The BD436S operates as a medium-power PNP bipolar junction transistor optimized for linear and switching roles where robust safe operating area (SOA) and stable DC current gain across collector current range are required. Its V_CEO(sus) = −32 V and I_C = −4 A define its primary use in low-to-medium frequency power amplification and DC load switching.

Thermal design is governed by its 36 W power dissipation at T_C = 25°C and derating curve down to zero at T_C = 175°C, while f_T = 3 MHz indicates suitability for audio-band and slow-switching applications-not RF or high-speed digital switching.

Key Specifications

Pinout & Package

BD436S is housed in a TO-126 plastic package with integral metal tab for heatsinking. The case is electrically connected to the collector terminal.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MJD436T4G and BD436, the BD436S offers identical performance to BD436 with guaranteed TO-126 mechanical compatibility and 36 W thermal capability - making it optimal for through-hole designs requiring robust heatsinking and legacy footprint support.

Availability

BD436S is available at Aetrix Electronics and suitable for audio amplifier output stages, DC motor drivers, linear voltage regulators, and relay/LED load switching requiring stable component supply and long-term industrial availability.

Supply support for BD436S 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 discrete devices, analog ICs, and interface solutions before its acquisition by ON Semiconductor in 2016.

The BD436S belongs to Fairchild's legacy medium-power bipolar transistor family, engineered for reliability in industrial linear and switching power applications where thermal stability and complementary NPN/PNP pairing are essential.

FAQ

What is the maximum continuous collector current rating for BD436S?

The BD436S has a maximum continuous collector current (I_C) rating of −4 A at T_C = 25°C. This rating assumes proper heatsinking; derating applies above 25°C case temperature per the published power derating curve. Pulse current capability reaches −7 A under specified test conditions (PW = 300 µs, duty cycle = 1.5%). The BD436S must not exceed these limits to maintain reliability and avoid thermal runaway.

Is BD436S pin-compatible with BD434 or BD438?

No, BD436S is not pin-compatible with BD434 or BD438 in terms of voltage rating or gain profile, though all share the same TO-126 package and pinout (Emitter–Collector–Base). BD434 is rated for −22 V, BD436S for −32 V, and BD438 for −45 V; substituting across this family without circuit revalidation risks overvoltage failure. The BD436S pinout matches BD436 exactly - not BD434 or BD438 - despite mechanical similarity.

What is the typical DC current gain (h_FE) of BD436S at I_C = −1 A?

At V_CE = −1 V and I_C = −1 A, the BD436S exhibits h_FE between 50 and 100 (typical range inferred from datasheet curves and adjacent test points). The official spec sheet guarantees h_FE ≥ 40 at I_C = −10 mA and ≥ 30 at I_C = −500 mA; performance at −1 A falls within the 40–140 overall range. Designers should verify gain at operating point using the Figure 1 characteristic curve in the BD436S datasheet.

Does BD436S require a heatsink in normal operation?

Yes, BD436S requires a heatsink for any sustained operation above ~1–2 W power dissipation. With a maximum P_C of 36 W at T_C = 25°C and thermal resistance θ_JC ≈ 0.7°C/W (inferred from TO-126 construction), even moderate loads (e.g., 2 A at 2 V V_CE) generate >4 W - exceeding natural convection limits. The metal tab is collector-connected and must be electrically isolated unless the heatsink is floating or biased accordingly. The BD436S thermal design must account for this constraint.

Can BD436S be used as a direct replacement for BD435 in a push-pull amplifier?

No - BD436S is a PNP transistor and BD435 is an NPN transistor; they are complementary, not interchangeable. In a push-pull stage, BD436S serves the negative half-cycle while BD435 handles the positive half-cycle. Swapping them would reverse polarity and prevent proper amplification. The BD436S is specifically intended as the PNP counterpart to BD435, enabling matched gain, voltage, and current capability in symmetrical output designs.