Power Electronics Lecture Series: Power BJ
Symbol, Structure, and Characteristics
Introduction to Power BJ
- Power BJ is a bipolar junction transistor used in power electronics.
- It has three terminals: base, emit, and collector.
- The symbol for N p configuration is depicted with an arrow head towards the emit terminal.
- Power BJ is designed to handle high power and has a larger cross-sectional area.
- We will focus on N p transistor for internal analysis and comparison with normal BJ.
Structure of Power BJ
- Power BJ has three layers: n plus, p, and n minus.
- The collector drift region is added for handling high breakdown voltage.
- The cross-sectional area and doping level are increased for power handling capacity.
- The symbol remains the same as normal BJ, but with additional layers.
- The structure is crucial for efficient power operation.
Characteristics of Power BJ
- Power BJ exhibits different modes in the output characteristics.
- These modes include cutoff, active, quasi-saturation, and hard saturation.
- Cutoff mode occurs when both junctions are reverse biased.
- Active mode functions as an amplifier and is not extensively covered in power electronics.
- Quasi-saturation offers advantages like lower on-state resistance and quick turn-off, making it suitable for high-frequency applications.
- Hard saturation has lower resistance and power loss but is used for low-frequency operation.