Infineon BC808-25E6327 PNP Transistor: Datasheet, Pinout, and Application Circuits

The Infineon BC808-25E6327 is a general-purpose PNP bipolar junction transistor (BJT) housed in a compact SOT-23 surface-mount package. Designed for a variety of amplification and switching applications, this component is a common choice in consumer electronics, automotive systems, and industrial control modules due to its robust performance and reliability.

Datasheet Overview and Key Specifications

The transistor is characterized by its low current and low voltage requirements, making it suitable for driver stages, signal processing, and low-power switching. Key absolute maximum ratings and electrical characteristics from its datasheet include:

Collector-Base Voltage (VCBO): -25 V

Collector-Emitter Voltage (VCEO): -20 V

Emitter-Base Voltage (VEBO): -5 V

Continuous Collector Current (IC): -500 mA

Total Power Dissipation (Ptot): 330 mW

DC Current Gain (hFE): 120 to 250 (at IC = -2 mA, VCE = -5 V)

Transition Frequency (fT): 100 MHz (typical)

These specifications highlight the device's capability to handle moderate currents while operating at a good speed, which is essential for amplification purposes.

Pinout Configuration

The BC808-25E6327 comes in an SOT-23 package with three pins. When viewing the component with the flat side facing you and the pins pointing downward, the pinout is as follows:

Pin 1 (Emitter): This is the input for the majority charge carriers in a PNP transistor.

Pin 2 (Base): The control pin. A current flowing out of this pin controls a larger current flowing from the emitter to the collector.

Pin 3 (Collector): The output pin, which collects the charge carriers from the emitter.

Correctly identifying this pinout is critical to preventing damage and ensuring the circuit functions as intended.

Application Circuits

The BC808-25E6327 is versatile and can be used in two primary modes: as a switch and as an amplifier.

1. Low-Side Switch Circuit:

One of the most common uses for this transistor is as a low-side switch, where it is placed between the load and ground. A typical circuit involves:

Connecting the load (e.g., a relay, motor, or LED) to the positive supply rail (Vcc).

Connecting the other terminal of the load to the transistor's collector.

Connecting the emitter directly to ground.

Using a series resistor (e.g., 1kΩ to 10kΩ) between a microcontroller's GPIO pin and the base of the transistor to provide the required base current to turn it on.

When a logic LOW (0V) is applied to the base resistor, the PNP transistor turns on, allowing current to flow from the emitter to the collector and through the load to ground, thereby activating it. A logic HIGH (e.g., 3.3V or 5V) at the base turns the transistor off.

2. Common-Emitter Amplifier:

For small-signal amplification, the BC808-25E6327 can be configured in a common-emitter amplifier setup. This circuit provides high voltage gain. Key components include:

A voltage divider network at the base to set the proper bias point (Q-point).

A collector resistor (RC) that converts the amplified collector current into a voltage output.

An emitter resistor (RE) to provide stability and negative feedback, preventing thermal runaway.

Coupling capacitors at the input and output to block DC offset while allowing the AC signal to pass.

This configuration is fundamental in audio pre-amplifiers, sensor signal conditioning, and other circuits where a small analog signal needs to be increased to a usable level.

Design Considerations

When implementing this transistor, designers must consider:

Base Resistor Calculation: The base current must be sufficient to drive the transistor into saturation for switching applications. The formula `IB > (IC / hFE)` is used to calculate the minimum base current.

Power Dissipation: Ensure that the product of the collector current (IC) and the collector-emitter voltage (VCE) does not exceed the maximum power rating of 330 mW, considering any derating for ambient temperature.

Anti-Saturation: In high-speed switching, a small capacitor in parallel with the base resistor can speed up the turn-on and turn-off times.

ICGOOODFIND: The Infineon BC808-25E6327 is a highly versatile and cost-effective PNP transistor that excels in low-power switching and amplification roles. Its combination of a sufficient current rating, good gain, and a small form factor makes it an excellent choice for modern electronic designs where board space and efficiency are paramount. Understanding its pinout and typical application circuits is key to leveraging its full potential.

Keywords: PNP Transistor, SOT-23, Low-Side Switch, Common-Emitter Amplifier, DC Current Gain (hFE)