BC328 Transistor PNP 25V 800mA

Description

Key Specifications

Key Characteristics & Applications

• High-Side Switching: Because it is a PNP transistor, the BC328 is the ideal choice for switching loads connected to the positive supply rail (High-Side). When the base is pulled to ground (or a voltage lower than the emitter), current flows from the Emitter to the Collector.

• Medium-Power Driver: With an 800mA capacity, it is robust enough to drive relays, solenoids, or strings of LEDs that would exceed the 100mA limits of smaller signal transistors like the BC556.

• Complementary Design: When paired with the BC338, you can create efficient H-bridge circuits for motor control or push-pull output stages for audio amplification.

Critical Implementation Notes

1. Voltage Limit (25V): The -25V $V_{CEO}$ limit is relatively low. This transistor is best used in systems powered by common battery voltages or regulated supplies (e.g., 5V, 9V, 12V). Do not use this in 24V systems where inductive spikes could easily push the voltage beyond the 25V breakdown threshold.

2. Base Drive: To switch a load at 800mA, you need to drive the base with enough current to achieve saturation. A base current of roughly $40mA – 80mA$ is recommended. If your logic source cannot provide this, use a small NPN transistor (like a 2N3904) to provide the necessary current pull.

3. Thermal Management: Like the BC338, it is housed in a TO-92 plastic package. Continuous operation at 800mA will cause the device to get quite hot. If you are operating at this level, ensure your PCB has adequate ground plane area for heat dissipation or use a small heatsink.

4. Flyback Protection: Always include a flyback diode (e.g., 1N4007) across any inductive load (motor/relay) to prevent the back-EMF from destroying the transistor when it switches “OFF.”

Comparison Table: Medium-Power Complementary Pairs