2N2222 Transistor and Its Applications

Hey everyone! I'm going to give you an introduction on the NPN Switching Transistor 2N2222 . It is currently the most widely used Negative-Positive-Negative (NPN) Bipolar Junction Transistor (BJT). The 2N2222 can be used for a variety of applications, including switching and amplification of analog signals. In this blog, we will be discussing its pinout, characteristics, features, specifications, applications, and circuit diagram.



2N2222 is the most commonly used NPN bipolar junction transistor. It can be used for switching applications and amplification of analog signals. The 2N2222 is enclosed in a TO-18 package.

2N2222 transistor is made of either silicon or germanium that has been saturated with either a positively or negatively charged material in a process called doping. A positively charged portion is placed between two negatively charged portions. Because the materials are arranged in the order negative, positive, negative, the device is known as an NPN transistor.

NPN transistor

When compared to other similar small transistors, one of its unique advantages is its capacity to handle high currents. It can normally switch an 800mA load current, which is a really high rating when compared to other similar transistors. While performing amplification applications, it receives an analog signal via collectors, and another signal is applied at its base. An Analog signal could be the voice signal having an analog frequency of almost 4kHz (human voice).


                 2N2222 transistor


NPN transistors, such as the 2N2222, are commonly employed in VHF (very high frequency) amplifiers and switching applications. The transistor is made up of silicon material. This type of transistor is considered a normal transistor and is used in the same way as an NPN transistor. Base, Emitter, and Collector are the three terminals on this transistor.

The 2N2222 transistor provides a constant DC collector current of 800mA, making it ideal for applications requiring low to medium current. It uses a 10ns delay time, 225ms storage time, 60ms fall time, and 25ms rise time to operate on a high transition frequency of 250MHz. It comes with the TO-92 bundle.



2N2222 transistor pinout
Pin Number Pin Name Description
1 Emitter Current flows out through emitter
2 Base Controls the biasing of the Transistor
3 Collector Current flows in through collector


Where to use 2N2222A

The 2N2222A transistor is very similar to the BC547 NPN transistor, which is widely used. However, there are two key differences between them. When compared to BC547, 2N2222 has a collector current of up to 800mA and a power dissipation of 652mW, allowing it to drive larger loads. It might be used in the same applications as the BC547 transistor, such as switching and amplification. It functions in two regions in the switching application: saturation and cut-off.

In the saturation area, complete current flows from the emitter to a collector with a current range of 110 to 800 mA, and it works as a switch. As a result, the user is only able to connect loads up to 800mA.

Similarly, when no current flows from emitter to collector in the cut-off region, it behaves as a switch that is turned off.

VI characteristics of Transistor

Active Mode

The transistor is generally used as a current amplifier in this mode. Two junctions are biased differently in active mode, with the emitter-base junction being forward biased and the collector-base junction being reverse biased. Current flows between the emitter and the collector in this mode, with the amount of current flow proportional to the base current.


Cutoff Mode

The collector-base junction and the emitter-base junction are reverse biased in this mode. There is no current flow except small leakage currents because both PN Junctions are reverse biased (usually in the order of a few nanoamps or pico amps). In this mode, the BJT is switched off and the circuit is an open circuit. Switching and digital logic circuits are primarily used in the Cutoff Region.

Saturation Mode

The emitter-base and collector-base junctions are forward biased in this region. With almost zero resistance, current flows freely from collector to emitter. The transistor is fully switched on in this mode, and the circuit is closed.  Saturation Region is also primarily used in switching and digital logic circuits.


2N2222 Applications

  • Audio Preamplifiers
  • As compared to the normal NPN BC547 transistor, the 2N2222 is extremely similar, but 2N2222 allows 800mA of collector current & also 652mW of power dissipation which can be utilized for driving larger loads as compared toBC547.
  • It is used for PWM due to its quick response
  • It is typically used in automation & embedded projects.
  • Darlington Pairs
  • Audio Amplifier Stages
  • Switching many loads at the same time 
  • RF Circuits
  • Sensor Circuits
  • It is mostly used in embedded and automation projects.


2N2222 transistor as a switch

One of the most common uses for transistors in an electronic circuit is simple switches. In other words, when a voltage is supplied to the base, a transistor conducts current across the collector-emitter. The switch is turned off when there is no base voltage. A transistor's switching operation is based on the voltage applied at the base terminal. The collector to emitter voltage is almost equal to 0 when a sufficient voltage (VIN > 0.7 V) is applied between the base and emitter. As a result, the transistor acts as a short circuit.  When no or zero voltage is applied to the input, the transistor works in the cutoff region and acts as an open circuit. The load (in this case, an LED) is linked to the switching output with a reference point in this type of switching connection. When the transistor is turned on, current flows from the source to the ground through the load.

Transistor as a Switch

The 2N2222 transistor is used as a switch in this circuit, with an input resistor driving the transistor and another resistor driving the LED. The transistor starts to work when the switch is closed, and the LED ON and OFF intervals are controlled by the resistance value.


2N2222 transistor as a switch


IC = VCC / RC, when VCE = 0 

 Base Current IB = IC / β




 An amplifier circuit can be defined as, a circuit that is used to increase the amplitude of a signal.  The amplifier's input is either a voltage or a current, and the output is an amplified input signal. A transistor can receive a weak signal through the base junction and release the amplified signal through the collector. Transistors are commonly used in RF (radio frequency), OFC (optical fiber communication), audio amplification, and other applications. We usually use the common-emitter configuration to make a transistor work as an amplifier.


Transistor as an amplifier


The amplification transistor circuit is designed in such a way that the input is always applied at the forward-biased junction. Similarly, the output can be collected across the transistor's reverse-biased junction. The input signal is applied to the base-emitter junction, and the output is sent to the emitter-collector junction through the load. This condition is essential because it accurately represents the amplification results. The transistor is given a low resistance value on the input side so that it can provide changes in the output value if the input signal changes significantly. In applications like audio amplifiers, the common emitter configuration is often used. Because in CB configuration, the gain is <1, and in CC configuration, the gain is almost equivalent to 1.


2N2222 transistor as an amplifier


Difference between 2N2222 and 2N2222A 

Diode 2N2222 2N2222A
Package TO-18 TO-92
Collector base Voltage 60V 75V
Collector emitter Voltage 30V 40V
Emitter base Voltage 5V 6V
DC Current gain 30 40
Base current 200mA 200mA
Collector current 800mA 800mA
Transition frequency 250MHz 300MHz
Collector Capacitance 8pF 8pF
Emitter capacitance  25pF 25pF
Total power dissipation 500mW 500mW
Noise  4dB 4dB
Max. Junction temperature 150 degree C 200 degree C
Turn off time 250ns 250ns


At last, hopefully, the 2N2222 transistor would be clear, now if you wish to buy any of these transistor then you may click on their names present down.



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