2N2222 NPN Transistor

Bi-Polar high current NPN Transistor

DC Current Gain (hFE) is 100
Continuous Collector current (IC) is 800mA
Emitter Base Voltage (VBE) is 6V
Collector Emitter Voltage (VCE) is 30V
Base Current (IB) is 5mA maximum

PKR 70/-

CATEGORY:Discrete Components

Product Description

2N2222A is a NPN transistor hence the collector and emitter will be left open (Reverse biased) when the base pin is held at ground and will be closed (Forward biased) when a signal is provided to base pin. 2N2222A has a gain value of 110 to 800, this value determines the amplification capacity of the transistor. The maximum amount of current that could flow through the Collector pin is 800mA, hence we cannot connect loads that consume more than 800mA using this transistor. To bias a transistor we have to supply current to base pin, this current (IB) should be limited to 5mA.

When this transistor is fully biased then it can allow a maximum of 800mA to flow across the collector and emitter. This stage is called Saturation Region and the typical voltage allowed across the Collector-Emitter (VCE) or Base-Emitter (VBE) could be 200 and 900 mV respectively. When base current is removed the transistor becomes fully off, this stage is called as the Cut-off Region and the Base Emitter voltage could be around 660 mV.

Pin Configuration

Pin 1 (Emitter): Current drains out through emitter
Pin 2 (Base): Controls the biasing of transistor
Pin 3 (Collector): Current flows in through collector

How to Use 2N2222A

This transistor can be used either as a switch or as an amplifier. The Base-Emitter voltage of this transistor is 6V so you just have to supply this voltage across the base and emitter of the transistor to induce a base current into the transistor. This will make it forward biased and close the connection between collector and emitter. However, one important thing to notice is the Base resistor, also known as the current limiting resistor. As the name suggests, this resistor will limit the current flowing through the transistor to prevent it from damage.

The value for this resistor can be calculated using the formula:

RB = VBE / IB

To illustrate, a simple circuit using a base voltage of 5V and a value of 1K for the current limiting resistor can be used to operate the transistor as a switch. In this circuit, the motor draws about 500mA from a 12V power source. Since the 2N2222 has a collector current rating up to 800mA, this configuration is feasible. Using a transistor with a lower rating, like a BC547, would cause it to burn out.