onsemi BD3796STU

Overview

BD3796STU from Fairchild Semiconductor is an NPN epitaxial silicon transistor designed for medium-power linear and switching applications, with V_CEO = 80 V, I_C = 2 A DC, P_C = 25 W at T_C = 25°C, h_FE = 100–250 (Class 10), and TO-126 package. It serves as a complement to BD380 in audio output and power switching stages.

For engineers reviewing the BD3796STU datasheet, pinout, applications, or equivalent options, key selection criteria include collector-emitter sustaining voltage (V_CEO(sus) = 80 V), saturation voltage (V_CE(sat) = 1 V @ I_C = 1 A, I_B = 0.1 A), safe operating area (SOA) limits, thermal derating curve, and h_FE classification consistency across production lots.

Technical Context

The BD3796STU is a single NPN bipolar junction transistor optimized for medium-power analog amplification and hard-switching duty. Its design emphasizes high breakdown voltage (V_CBO = 100 V), robust pulse current capability (I_CP = 3 A), and stable DC current gain (h_FE1 = 100–250 at I_C = 0.15 A, V_CE = 2 V).

It operates within a junction temperature range of –55°C to +150°C and exhibits fast switching performance with t_ON = 50 ns and t_OFF = 500 ns under specified test conditions (V_CC = 30 V, R_L = 60 Ω, I_B1 = –I_B2 = 0.05 A), supporting reliable use in Class AB audio output and relay driver circuits.

Key Specifications

Pinout & Package

BD3796STU is housed in a through-hole TO-126 package with standardized mechanical dimensions (16.10 × 13.06 × 4.2 mm max), integral metal tab for heatsinking, and three leads: Emitter (Pin 1), Collector (Pin 2), Base (Pin 3).

Key Features

Applications

Equivalent & Alternatives

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

Compared with BD3796STU, MJD31C offers higher voltage headroom and current capacity but lacks h_FE binning and uses a larger TO-220 package, while BD139 provides identical voltage ratings but insufficient power handling for continuous 2 A operation-making BD3796STU the optimal balance of SOA, gain control, and form factor for medium-power linear and switching roles.

Availability

BD3796STU is available at Aetrix Electronics and suitable for audio power amplifiers, DC motor drivers, relay interface circuits, and linear voltage regulators requiring stable component supply and long-term industrial availability.

Supply support for BD3796STU 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 BD3796STU belongs to Fairchild's BD37x series of medium-power NPN transistors engineered for cost-sensitive, high-reliability linear and switching applications in consumer audio, industrial controls, and power management subsystems.

FAQ

What is the maximum continuous collector current rating for BD3796STU?

The BD3796STU has a maximum continuous collector current (I_C) rating of 2 A at T_C = 25°C. Derating is required above this case temperature per the published power derating curve-e.g., at T_C = 75°C, the usable I_C drops to approximately 1.3 A to maintain P_C ≤ 12.5 W. This rating assumes adequate heatsinking and proper PCB copper area for thermal conduction.

Is BD3796STU pin-compatible with BD375 or BD377?

Yes, BD3796STU shares the same TO-126 package and identical pinout (Emitter–Collector–Base) with BD375 and BD377. However, it is not a drop-in replacement due to higher voltage ratings: BD3796STU specifies V_CEO = 80 V and V_CBO = 100 V versus 45 V/50 V for BD375. Substituting BD3796STU into a BD375 design is safe; reverse substitution risks breakdown.

What h_FE classification does BD3796STU carry, and how is it verified?

BD3796STU is classified as h_FE Class 10, meaning its DC current gain falls within 100–250 when measured at V_CE = 2 V and I_C = 0.15 A. This binning is performed during final test at Fairchild's manufacturing site and marked on the device body per internal lot traceability standards-not indicated in the part number itself but confirmed in the original Rev. A datasheet.

Can BD3796STU be used in switching power supplies above 100 kHz?

BD3796STU is not recommended for hard-switching power supplies operating above 100 kHz. Its t_OFF = 500 ns and lack of optimized charge storage characteristics limit practical efficiency above ~300 kHz. For such applications, modern MOSFETs or RF-optimized BJTs with sub-100 ns switching times and lower Q_g are preferred. BD3796STU remains suitable for <50 kHz PWM motor control and line-frequency SMPS auxiliary supplies.

Does BD3796STU require a heatsink in typical linear amplifier use?

Yes, BD3796STU requires a heatsink in any linear amplifier application dissipating >3 W continuously. At 25 W P_C, even with a 2°C/W heatsink and 25°C ambient, junction temperature would exceed 150°C without forced airflow. For Class AB audio output stages delivering 10–15 W, a 4–6°C/W extruded aluminum heatsink with thermal interface pad is typically sufficient to maintain T_J < 125°C under worst-case bias conditions.