BC239 NPN Transistor Pinout Datasheet

Introduction

The BC239 NPN transistor is a low-noise, small-signal silicon transistor designed primarily for audio frequency (AF) amplification and low-level signal processing. It belongs to the BC23x transistor family (BC237, BC238, BC239) and is recognized for its excellent low noise characteristics, high gain stability, and reliability in analog circuits. The BC239 is most commonly found in audio preamplifiers, microphone amplifiers, and signal conditioning stages where clean, distortion-free output is crucial.

Constructed in the TO-92 plastic package, this transistor operates efficiently in both commercial and hobbyist electronic designs. With a maximum collector current of 100mA and collector-emitter voltage of 25V, it performs well in low-voltage applications. Its high transition frequency (fT) ensures stable operation even in mid-frequency amplifier circuits, making it ideal for use in hi-fi audio and instrumentation circuits.

BC239 NPN Transistor

The BC239 offers superior performance compared to other general-purpose NPN transistors due to its low input noise voltage and high DC current gain (hFE). Its electrical characteristics are closely matched with its family counterparts (BC237 and BC238), but the BC239 is specifically optimized for low noise operation, making it the preferred choice in high-fidelity and precision electronic equipment.

BC239 Pinout

Pin Configuration

Pin#	Pin Name	Pin Description
1	Collector (C)	The output terminal where current flows from collector to emitter when the transistor is ON.
2	Base (B)	Controls the transistor’s operation by allowing a small base current to regulate a larger collector current.
3	Emitter (E)	The terminal through which current leaves the transistor; usually connected to ground or the negative supply line.

BC239 Pin Configuration

Key Features

Low noise NPN silicon transistor
High current gain and stable amplification
Ideal for low-level and high-fidelity audio circuits
Designed for small signal and general-purpose applications
Compact TO-92 plastic package for easy PCB mounting
High reliability and thermal stability
Complementary to BC329 (PNP)

Characteristics

Transistor Type: NPN
Collector-Emitter Voltage (Vceo): 25V
Collector-Base Voltage (Vcbo): 30V
Emitter-Base Voltage (Vebo): 5V
Maximum Collector Current (Ic): 100mA
DC Current Gain (hFE): 200 – 800 (typical)
Transition Frequency (fT): 100MHz
Power Dissipation (Ptot): 500mW
Noise Figure: 2dB (typical)
Operating Temperature Range: -65°C to +150°C
Package Type: TO-92

Comparison : BC237 vs BC238 vs BC239

The BC237, BC238, and BC239 transistors are all part of the same low-noise, small-signal NPN family. They share the same TO-92 package, current handling capability, and general-purpose nature. The main difference lies in their maximum voltage ratings and noise performance.

The BC237 offers a moderate collector-emitter voltage rating of 45V, making it versatile for most signal applications. The BC238 supports slightly higher voltage levels (up to 50V), while the BC239 is optimized for ultra-low noise audio applications, making it a preferred choice in high-fidelity amplifiers and sensitive input stages. In general, they are electrically interchangeable for most low-power circuits, with the BC239 offering the best noise performance, followed by BC238 and BC237.

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Key Applications of BC239 Transistor

Low noise audio frequency amplifiers
Microphone preamplifier and tone control stages
Signal and sensor amplification circuits
Low distortion AF driver and pre-driver circuits
General-purpose low power switching applications
Laboratory, hobbyist, and educational electronic projects

PNP Complementary Transistor

BC329 is the PNP complementary transistor for BC239.
It matches closely in characteristics and is used in push-pull amplifier stages or complementary pair designs to ensure balanced and distortion-free output.

Equivalent of BC239 NPN Transistor

BC237, BC238, 2N3904, BC547, BC549, 2SC1815, S8050, KTN2222A
These equivalents can replace BC239 in most small-signal and low-noise circuits with minor circuit adjustments.

Always verify pin configuration and voltage ratings before substitution.

Datasheet of BC239 NPN Transistor

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Download Datasheet

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