STMicroelectronics BD135-16

Overview

BD135-16 from STMicroelectronics is an NPN epitaxial planar bipolar junction transistor in SOT-32 package, designed for audio amplifier and driver stages in complementary or quasi-complementary circuits. It delivers 1.5 A continuous collector current, 45 V collector-emitter sustaining voltage (V_CEO(sus)), DC current gain (h_FE) of 100–160 at I_C = 150 mA, and 12.5 W total power dissipation at T_C ≤ 25 °C.

For engineers reviewing the BD135-16 datasheet, BD135-16 pinout, BD135-16 application, or BD135-16 equivalent, key selection criteria include guaranteed h_FE group (16), V_CEO(sus) rating, thermal resistance (R_thj-case = 10 °C/W), safe operating area (SOA) curves, and compatibility with complementary PNP BD136-16 in push-pull output stages.

Technical Context

The BD135-16 operates as a linear amplifying device with fixed-base biasing capability and defined SOA boundaries up to 300 µs pulse width. Its h_FE grouping (100–160) ensures consistent current amplification across production lots, while the 45 V V_CEO(sus) and 0.5 V V_CE(sat) at I_C = 0.5 A support Class AB audio output stage operation.

Thermal design relies on case-mounted heatsinking due to R_thj-case = 10 °C/W and R_thj-amb = 100 °C/W; junction temperature must remain ≤150 °C under steady-state or pulsed conditions per Figure 2 and Figure 3 derating curves.

Key Specifications

Pinout & Package

SOT-32 (TO-126) plastic package with integral metal tab for heatsink attachment; pin 1 = emitter, pin 2 = base, pin 3 = collector (tab-connected). Mounting requires electrically isolated thermal interface if collector is not at ground potential.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BD135-16, BD139-16 offers higher voltage headroom without sacrificing gain matching, while MJE13005 trades precision linearity for rugged high-voltage switching-making it incompatible for audio output but viable for flyback transformer drivers.

Availability

BD135-16 is available at Aetrix Electronics and suitable for audio amplifier output stages, quasi-complementary driver circuits, and DC motor control applications requiring stable component supply and consistent h_FE binning.

Supply support for BD135-16 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

STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, designing and manufacturing analog, digital, and mixed-signal ICs and discrete devices for industrial, automotive, and consumer markets.

The BD135-16 belongs to ST's legacy bipolar power transistor family optimized for linear audio and general-purpose amplification, emphasizing gain consistency, thermal reliability, and manufacturable SOT-32 packaging for cost-sensitive discrete amplifier designs.

FAQ

What does the "-16" suffix indicate in BD135-16?

The "-16" suffix denotes the h_FE gain group: BD135-16 is pre-selected to deliver DC current gain between 100 and 160 when measured at I_C = 150 mA and V_CE = 2 V. This binning enables predictable matching with complementary BD136-16 transistors in push-pull amplifier outputs, reducing gain mismatch and crossover distortion.

Can BD135-16 be used in place of BD135 without modification?

Yes-BD135-16 is a direct replacement for generic BD135 in all electrical and mechanical respects. The only difference is tighter h_FE specification (100–160 vs. 25–250 for standard BD135). No circuit changes are needed, but performance benefits include improved gain predictability and better pairing consistency with BD136-16 in complementary designs.

Is BD135-16 suitable for switching power supplies?

No-BD135-16 is optimized for linear operation in audio and driver applications, not high-frequency switching. Its relatively slow transition frequency (f_T ≈ 50 MHz, inferred from typical BD135 characteristics), lack of specified switching times, and SOA validation only up to 300 µs make it unsuitable for SMPS use. For switching, consider purpose-built transistors like MJD122 or BUJ302A with documented t_on/t_off and SOA at high frequency.

How should the metal tab on the SOT-32 package be handled thermally and electrically?

The metal tab is internally connected to the collector (pin 3). When mounted to a heatsink, use an electrically isolating thermal pad or mica washer unless the heatsink is floating or referenced to collector potential. Mechanical pressure must ensure uniform contact; torque on mounting screw should not exceed 0.5 N·m to avoid package cracking. Thermal interface material must cover ≥80% of tab surface for optimal R_thj-case performance.