2N2222 Transistor Overview

The 2N2222 is an NPN transistor that operates in two main states based on the base pin voltage. When the base is grounded, the collector and emitter are reverse-biased (open). When a signal is applied to the base, it becomes forward-biased (closed).

Key Specifications:

• Gain (hFE): Ranges from 110 to 800, indicating its amplification capacity.
• Maximum Collector Current: 800mA. Loads drawing more than this cannot be connected.
• Base Current (IB): Should be limited to 5mA for proper biasing.

In the saturation region, when fully biased, the transistor can allow up to 800mA to flow between the collector and emitter. Typical voltage drops in this state are around 200mV across the collector-emitter (VCE) and about 900mV across the base-emitter (VBE). When the base current is removed, the transistor enters the cut-off region, with a base-emitter voltage of approximately 660mV.

Applications:

• Switching high-current loads (up to 800mA)
• Various switching applications
• Motor speed control
• Inverters and rectifier circuits
• Configurations in Darlington pairs