The Original BD136 PNP Medium-Power Silicon Bipolar Junction Transistor (45V / 1.5A / SOT-32 / TO-126) is a versatile, complementary silicon epitaxial planar transistor engineered for audio frequency amplification, linear driver stages, and general-purpose DC switching applications. Rated for a maximum collector-emitter voltage of 45V and continuous collector current handling up to 1.5A, it delivers robust current gain and low saturation voltage. While occasionally cross-referenced or mislabeled in compact footprints, the BD136 is manufactured in the classic 3-lead plastic power package with an integrated metal mounting hole (SOT-32 / TO-126 / TO-225AA) for easy heatsink attachment. It is widely used as a high-side driver, relay/solenoid actuator, class-AB audio output driver, and complementary PNP pair alongside the NPN BD135 or BD139.

Specifications

• Part Number: BD136 (Complementary to NPN BD135 / BD139)
• Transistor Polarity: PNP Epitaxial Planar Silicon BJT
• Package Type: SOT-32 / TO-126 (Plastic 3-Lead Power Package with Center Heatsink Screw Hole)
• Collector-Emitter Voltage ($V_{CEO}$): -45 V (Max. with base open)
• Collector-Base Voltage ($V_{CBO}$): -45 V (Max. with emitter open)
• Emitter-Base Voltage ($V_{EBO}$): -5.0 V (Max. with collector open)
• Continuous Collector Current ($I_C$): -1.5 A
• Peak Collector Current ($I_{CM}$): -3.0 A (Pulsed)
• Continuous Base Current ($I_B$): -0.5 A
• Total Power Dissipation ($P_D$):
  • At $T_C = 25^\circ\text{C}$ (Mounted on Heatsink): 12.5 W
  • At $T_A = 25^\circ\text{C}$ (Free Air Ambient): 1.25 W
• DC Current Gain ($h_{FE}$):
  • At $V_{CE} = -2\text{V}$, $I_C = -150\text{mA}$: 40 to 250 (Typ. BD136-10: 63–160, BD136-16: 100–250)
  • At $V_{CE} = -2\text{V}$, $I_C = -500\text{mA}$: Min. 25
• Collector-Emitter Saturation Voltage ($V_{CE(sat)}$): Max. -0.5 V (at $I_C = -500\text{mA}$, $I_B = -50\text{mA}$)
• Base-Emitter Saturation Voltage ($V_{BE(sat)}$): Max. -1.0 V (at $I_C = -500\text{mA}$, $I_B = -50\text{mA}$)
• Transition Frequency ($f_T$): Typ. 190 MHz (at $V_{CE} = -5\text{V}$, $I_C = -50\text{mA}$, $f = 100\text{MHz}$)
• Thermal Resistance (Junction-to-Case, $R_{\theta JC}$): 10 °C/W
• Thermal Resistance (Junction-to-Ambient, $R_{\theta JA}$): 100 °C/W
• Operating Junction Temperature ($T_j$): -55°C to +150°C
• Storage Temperature Range ($T_{stg}$): -55°C to +150°C
• Pinout Configuration (TO-126 / SOT-32 - Front Printed Face, Pins Facing Down):
  • Pin 1: Emitter (E)
  • Pin 2: Collector (C) - Connected to center metal mounting backplate
  • Pin 3: Base (B)

Features

• Medium-Power 1.5A Current Capacity: Capable of driving mid-level inductive loads, relays, solenoids, small DC motors, and high-intensity indicator lamps directly.
• High Transition Frequency ($f_T \approx 190\text{ MHz}$): High gain-bandwidth product enables crisp frequency response in audio preamps, push-pull driver stages, and high-speed analog linear amplifiers.
• Complementary Pairing: Perfectly matched electrical parameters for complementary symmetry configurations paired with the NPN **BD135** or **BD139**.
• Low Saturation Voltage ($V_{CE(sat)} \le 0.5\text{V}$): Minimizes on-state conduction power losses during saturation in high-side switching circuits.
• Versatile Mounting Package: SOT-32 / TO-126 footprint allows stand-alone free-air PCB placement or direct screw mounting onto an aluminum heatsink for high-power thermal dissipation.

Common Applications

• Audio Power Amplifiers: Class-AB push-pull driver stages, complementary output pairs, and headphone/line amplifiers.
• High-Side DC Switching: High-side PNP power switching for relays, 12V/24V LED arrays, solenoids, and DC motors.
• Linear Voltage Regulators & Pass Transistors: Series-pass PNP element in low-dropout (LDO) linear regulators and active current limiters.
• Microcontroller Interfacing: Amplifying weak GPIO outputs from Arduino, ESP32, or STM32 to drive heavier DC loads.
• H-Bridge Direction Controllers: High-side PNP switching legs in discrete bidirectional DC motor H-bridge circuits.

Usage Tips

• Package Identification Note: The BD136 belongs to the standard **SOT-32 / TO-126** medium-power package family (with a flat backplate and center M3 mounting screw hole). Always verify the physical dimensions and lead layout on your board.
• Pinout Verification (E-C-B): Unlike general small-signal TO-92 transistors (which often follow E-B-C or C-B-E), the standard BD136 in TO-126 is pinned as **1: Emitter, 2: Collector, 3: Base** (viewed from the front printed face with leads pointing downward).
• Thermal Management & Heatsinking: In free air without a heatsink, power dissipation must not exceed **1.25W**. For continuous collector currents above **300mA to 500mA**, screw the transistor onto a small aluminum heatsink using thermal paste.
• Base Drive Current Calculation: To ensure full saturation as a switch, supply sufficient base current using the standard rule of thumb ($I_B \approx I_C / 10$ to $I_C / 20$). Size the base series resistor accordingly: $R_B = (V_{IN} - V_{BE}) / I_B$.
• Inductive Flyback Protection: When using the BD136 to switch inductive loads (relays, motors, solenoids), always place a fast freewheeling diode (e.g., 1N4007 or 1N4148) in reverse-parallel across the load to suppress inductive voltage spikes.

Datasheet