onsemi BD436STU

Overview

BD436STU from Fairchild Semiconductor is a PNP epitaxial silicon transistor designed for medium-power linear and switching applications, with −32 V collector-emitter sustaining voltage (V_CEO(sus)), −4 A DC 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 a complement to BD435 in audio output stages and power control circuits.

For engineers reviewing the BD436STU 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, complementary pairing with BD435, and suitability for industrial relay drivers and linear regulator pass elements.

Technical Context

The BD436STU operates as a medium-power PNP bipolar junction transistor with fixed emitter-base and collector-base junction structures optimized for stable DC gain and low saturation voltage across its rated current range. Its safe operating area (SOA) supports pulsed operation up to −7 A with 1.5% duty cycle, and thermal derating begins at T_C = 25°C with linear reduction to zero dissipation at 150°C case temperature.

Designed for linear amplification and hard-switching roles, the device exhibits V_BE(on) = −1.1 V at I_C = −2 A, f_T = 3 MHz at V_CE = −1 V, and leakage currents (I_CBO, I_CEO) ≤ −100 µA under rated blocking conditions - confirming suitability for bias-stable amplifier stages and low-leakage off-state switching.

Key Specifications

Pinout & Package

BD436STU is housed in a TO-126 plastic package with integral metal tab for heatsink mounting. 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 BD436STU offers identical transistor performance in a through-hole TO-126 package optimized for manual prototyping and heatsink-mounted industrial designs, while BD436 provides the same silicon in bulk packaging and MJD436T4G shifts to surface-mount with minor voltage and gain trade-offs.

Availability

BD436STU is available at Aetrix Electronics and suitable for industrial relay drivers, audio amplifier output stages, and linear voltage regulator pass elements requiring stable component supply and long-lifecycle support.

Supply support for BD436STU 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 components before its acquisition by ON Semiconductor in 2016.

The BD436STU belongs to Fairchild's legacy medium-power bipolar transistor family, engineered for robust linear amplification and switching in industrial and audio systems where thermal stability and complementary pairing are critical.

FAQ

What is the maximum continuous collector current rating for BD436STU?

The BD436STU has a maximum continuous collector current (I_C) rating of −4 A at T_C = 25°C. This rating assumes adequate heatsinking; derating is required above 25°C case temperature per the linear power derating curve in the datasheet. At T_C = 100°C, the usable I_C drops to approximately −2.2 A. The BD436STU must be mounted to a heatsink meeting thermal resistance requirements to sustain this current continuously.

Is BD436STU pin-compatible with BD435?

No, BD436STU is not pin-compatible with BD435. BD436STU is a PNP transistor in TO-126 package with pinout Emitter–Collector–Base (1–2–3), while BD435 is an NPN device with the same physical package but reversed polarity and complementary pin assignment. They are functional complements-not mechanical replacements-and require mirrored circuit placement in push-pull designs. The BD436STU pinout remains consistent with other BD43x PNP variants.

What is the collector-emitter sustaining voltage (V_CEO(sus)) of BD436STU?

The BD436STU has a collector-emitter sustaining voltage (V_CEO(sus)) of −32 V, measured at I_C = −100 mA and I_B = 0. This parameter defines the maximum voltage the device can block in active mode before entering uncontrolled conduction. It is distinct from breakdown voltage and reflects practical switching capability under real-world load conditions. This rating makes the BD436STU suitable for 24 V industrial systems with safety margin.

Does BD436STU require a heatsink in normal operation?

Yes, BD436STU requires a heatsink for any sustained operation above ~0.5 A collector current or when dissipating more than ~2 W. Its 36 W maximum power dissipation is only achievable at T_C = 25°C - a condition impossible without active cooling. For example, at 2 A and V_CE(sat) ≈ −0.3 V, power dissipation is ~0.6 W, which may be manageable with minimal copper; however, linear regulator or audio output use cases routinely demand full heatsinking to maintain junction temperature below 150°C.

What is the DC current gain (h_FE) range for BD436STU at different operating points?

The BD436STU exhibits h_FE = 40–140 depending on test conditions: minimum 40 at V_CE = −5 V, I_C = −10 mA; minimum 30 at V_CE = −1 V, I_C = −500 mA; and up to 140 at V_CE = −1 V, I_C = −2 A. This wide spread reflects typical bipolar transistor behavior - gain decreases at low current and high voltage. Designers should reference the h_FE vs. I_C curve in the BD436STU datasheet to select appropriate base drive for target operating points.