onsemi BD137

Overview

BD137 from onsemi is a plastic medium-power silicon NPN transistor designed for audio amplifier and driver stages in complementary or quasi-complementary circuits, with V_CEO = 60 V, I_C = 1.5 A, P_D = 12.5 W at T_C = 25°C, h_FE ≥ 40 at I_C = 0.15 A, and TO-225 package.

For engineers reviewing the BD137 datasheet, pinout, applications, or equivalent options, key selection considerations include its 60 V collector-emitter sustaining voltage, 1.5 A continuous collector current capability, thermal resistance of 10 °C/W junction-to-case, suitability for linear audio output stages, and Pb-free TO-225 packaging.

Technical Context

The BD137 operates as a linear bipolar junction transistor with fixed NPN polarity, intended for Class AB audio output amplification and medium-power switching where gain stability and saturation voltage control are critical. Its DC current gain (h_FE) ranges from 40 to 250 depending on collector current, and it supports operation across –55°C to +150°C junction temperature.

It features complementary pairing with BD138 (PNP), enabling push-pull configurations without external bias network redesign. The device uses silicon epitaxial planar construction and meets RoHS, Pb-free, halogen-free, and BFR-free compliance requirements per onsemi's manufacturing standards.

Key Specifications

Pinout & Package

BD137 is housed in a TO-225 package (Case 77-09, Style 1), featuring three leads plus an internal collector-connected tab (pins 2 and 4 both serve as collector terminals). The package is thermally optimized for through-hole mounting with mechanical lug options and complies with ASME Y14.5M dimensioning standards.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BD137, BD139G offers higher voltage ratings while maintaining identical pinout and thermal performance-ideal for future-proofing 60 V designs. MJE13003 trades gain and linearity for high-voltage ruggedness, making it unsuitable for audio but viable in switched-mode power conversion where BD137 would fail catastrophically.

Availability

BD137 is available at Aetrix Electronics and suitable for audio power amplifiers, DC motor drivers, linear voltage regulators, and overcurrent protection circuits requiring stable component supply and long-term industrial availability.

Supply support for BD137 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

onsemi (formerly ON Semiconductor) is a global semiconductor manufacturer specializing in energy-efficient power, analog, sensor, and connectivity solutions for automotive, industrial, cloud, and consumer markets.

The BD137 belongs to onsemi's legacy medium-power bipolar transistor family, engineered specifically for cost-sensitive, high-reliability linear amplification and driver applications where thermal stability and gain consistency are essential.

FAQ

What is the maximum collector-emitter voltage rating for BD137?

The BD137 has a maximum collector-emitter sustaining voltage (V_CEO) of 60 V under specified test conditions (I_C = 0.03 A, I_B = 0). This rating defines the absolute upper limit for DC or peak AC voltage applied between collector and emitter with the base open. Exceeding this value risks avalanche breakdown and permanent device failure. Always maintain at least 20% design margin in practical BD137 applications.

Is BD137 pin-compatible with BD135G and BD139G?

Yes, BD137 is fully pin-compatible with BD135G and BD139G - all three share identical TO-225 (Case 77-09, Style 1) packaging, pin assignment (Pin 1 = Emitter, Pins 2 & 4 = Collector, Pin 3 = Base), and mechanical footprint. However, their voltage ratings differ: BD135G = 45 V, BD137 = 60 V, BD139G = 80 V. Substitution requires verification of voltage headroom in the target BD137 circuit.

What is the typical DC current gain (hFE) of BD137 at 0.5 A collector current?

The BD137 datasheet specifies h_FE min = 25 at I_C = 0.5 A, V_CE = 2 V. Typical values observed in production units range from 45 to 90 under those conditions. This gain level supports reliable base drive design for medium-current switching or linear amplification, though actual h_FE varies with temperature and individual unit dispersion. For critical BD137 designs, verify gain in-circuit or apply worst-case tolerance analysis.

Can BD137 be used in surface-mount applications?

No, BD137 is exclusively offered in the through-hole TO-225 package and is not available in any surface-mount variant. Its mechanical design - including the metal tab for heatsinking and lead spacing - is optimized for PCB mounting with soldering iron or wave soldering. Attempting SMT reflow will damage the BD137 due to thermal stress and misalignment. For SMT alternatives, consider SOT-223 or DPAK packaged transistors with comparable specs, but note they are not functionally identical to BD137.

Does BD137 require a heatsink in normal operation?

Yes, BD137 requires a heatsink whenever power dissipation exceeds ~2.5 W at ambient temperatures above 40°C. With R_JA = 100 °C/W and R_JC = 10 °C/W, even at 5 W dissipation, junction temperature rises ~50°C above case - easily exceeding safe limits without thermal management. The BD137 metal tab must be electrically isolated and thermally coupled to the heatsink using appropriate insulating pads and thermal compound to ensure reliable BD137 operation in continuous-duty applications.