BD159

Product Overview

The onsemi BD159 is a high-voltage, high-current NPN silicon power transistor intended for general-purpose power amplification and switching applications. Known for its durability and robust performance, the BD159 is widely used in industrial, automotive, and power electronics systems. It offers a higher collector-emitter voltage rating than typical medium-power transistors, making it suitable for circuits that require operation at elevated voltages and moderate currents.

The BD159 is commonly packaged in a TO-126 plastic case, which offers a compact footprint while allowing for effective thermal dissipation with a heat sink. Its high breakdown voltage and good gain characteristics over a wide current range make it appropriate for audio amplification stages, motor control, relay driving, and regulated power supplies.

Key Features

* NPN silicon power transistor for high-voltage switching and linear applications
* Collector-emitter voltage rating up to 80 V
* Continuous collector current up to 2 A
* High DC current gain with stable performance over a wide current range
* Suitable for linear and switching applications
* TO-126 package for compact mounting with heat dissipation
* Complementary to the BD160 PNP transistor for symmetric design architectures
* Wide safe operating area (SOA) with thermal and electrical ruggedness

Electrical Specifications

* Transistor Type: NPN
* Collector-Emitter Voltage (V_CEO): 80 V
* Collector-Base Voltage (V_CBO): 100 V
* Emitter-Base Voltage (V_EBO): 5 V
* Collector Current (I_C): 2 A continuous
* Base Current (I_B): Max 0.5 A
* Total Power Dissipation (P_TOT): 12.5 W @ T_C = 25 °C with heat sink
* DC Current Gain (h_FE):

* 40 to 250 depending on test conditions
* Typically 40–100 at I_C = 1 A, V_CE = 5 V
* Collector-Emitter Saturation Voltage (V_CE(sat)):

* Typically 0.5 V at I_C = 1 A, I_B = 100 mA
* Transition Frequency (f_T): ~3 MHz (low-frequency optimized)
* Operating and Storage Temperature Range: –55 °C to +150 °C
* Package Type: TO-126 (fully encapsulated, mounting hole for heat sink)

Functional Description

The BD159 is designed to handle moderate power levels while offering higher voltage headroom than lower-rated general-purpose transistors. As an NPN device, it conducts when a positive voltage is applied to the base relative to the emitter. It is suitable for both analog amplification and digital switching, providing versatility across a wide spectrum of applications.

Its high breakdown voltage and 2 A collector current rating allow it to drive loads such as motors, solenoids, lamps, and other inductive or resistive components. The high DC gain ensures that the transistor can be fully saturated or biased into linear operation with modest base currents, making it ideal for designs where base current is limited.

In audio applications, it serves well in driver or output stages for power amplifiers. In industrial and automotive systems, it is frequently used in high-side and low-side switching roles or in voltage regulation circuitry.

Typical Applications

* Power amplifiers (driver and output stages)
* Switching regulators and voltage-controlled power supplies
* Relay and solenoid drivers
* Motor driver circuits
* Industrial control systems and automation
* Push-pull and complementary amplifier designs (when paired with BD160)
* Lamp drivers and power inverters
* General-purpose high-voltage switching

Design Considerations

* Thermal Management: Although the TO-126 package supports up to 12.5 W dissipation with a proper heat sink, designers must ensure adequate cooling to maintain junction temperature within safe limits.
* Biasing and Drive: Sufficient base current must be supplied for full saturation in switching applications; overdrive may be needed at higher collector currents.
* Switching Speed: The BD159 is not intended for high-frequency applications (transition frequency ~3 MHz); it performs best in audio and low-frequency power switching.
* SOA Compliance: Always verify operation within the transistor’s safe operating area, especially when switching inductive loads or under high-voltage, high-current conditions.
* Heat Sink Insulation: The collector is usually connected to the metal tab in TO-126; isolation pads may be needed when mounting to grounded or electrically sensitive surfaces.
* Complementary Pairing: For symmetrical designs or full-bridge configurations, the BD160 (PNP) is a recommended complement.

Summary

The onsemi BD159 is a rugged and reliable NPN power transistor suited for high-voltage, medium-current applications in both switching and analog domains. Its 80 V collector-emitter rating and 2 A current capability make it versatile for use in motor control, audio amplification, industrial automation, and power supply systems. The TO-126 package, wide SOA, and good gain characteristics ensure dependable performance in environments where voltage robustness and thermal reliability are key design priorities.