What is a 2N2222A Transistor & Its Working

The NPN transistor like 2N2222 is most frequently used for VHF (very high frequency) amplifier & switching applications. The design of this transistor can be done using silicon material. This kind of transistor is considered a normal transistor, so it is used like an NPN transistor. It is used as a small signal transistor frequently. This article discusses an overview of a 2N2222A transistor.

What is a 2N2222A Transistor?

The 2N2222A transistor is a common NPN BJT & it is mainly used in the applications of switching & amplifying with less power. This transistor is mainly designed for low power, low to medium current, medium voltage & works at fairly high speeds.

In the 2N2222 NPN transistor, a single P-doped layer is embedded among two N-doped layers. This transistor includes three terminals like Base, Emitter & Collector. 2N2222A transistor symbol is shown below.

2N2222A Transistor
2N2222A Transistor

2N2222A transistor offers constant DC collector current like 800mA, so it is necessary to use where low to medium current is necessary. It functions on the value of high transition frequency like 250MHz through 10ns delay time, 225ms storage time, 60ms fall time & 25ms rise time. It is available in the TO-92 package.

Alternative 2N2222A transistors are; BC636, BC549, BC639, 2N2369, BC547, 2N3055, 2N3906, 2N3904 & 2SC5200. Equivalent 2N2222 transistors are; 2N3904 (PNP), 2N2907 (PNP), 2N3906 (PNP), S9014, BC637, BC148, MPS2222, 2N4403, PN2222, KTN2222 & KN2222.

2N2222A Transistor Pin Configuration

The pin configuration of the 2N2222A transistor is shown below. This transistor includes three pins & its each pin functionality is discussed below.

2N222A Pin Configuration & Symbol
2N222A Pin Configuration & Symbol
  • Pin1 (Collector): This is the first pin of the transistor & it is an o/p pin. The main function of this pin is to provide transistor current toward the o/p load.
  • Pin2 (Base): The base pin is a control pin & it is a second pin of the transistor. The main function of this pin is to control the current from emitter to base.
  • Pin3 (Emitter): The emitter pin is the third pin of the transistor & it is used to drain out the complete current of the transistor.

Features & Specifications

The features & specifications of the 2N2222 NPN transistor include the following.

  • The polarity of Transistor – NPN
  • Type of termination –Through Hole
  • Configuration of pin – a
  • Number of Pins -3
  • The voltage from collector terminal to emitter is 50V once the base terminal is open
  • The voltage from the emitter to the base terminal is 6V once the collector terminal is open
  • The voltage from the collector terminal to the base is 75V once the emitter terminal is open
  • The current Gain of DC is 100
  • DC collector current is 800mA
  • Accessible in the Package of To-92
  • Total power dissipation is 1W
  • The maximum base current is 5mA
  • Input capacitance is 25pF
  • Fall time is 60ns
  • Output capacitance is 8pF
  • Turn-on time is 25ns

The configuration modes of the 2N2222 NPN transistor include common emitter (CE), common collector (CC) & common base (CB). These three configurations are very helpful for amplifying voltage, current & power very easily in different applications based on the requirement.

How to use 2N2222A Transistor?

The touch switch circuit using the 2N2222A transistor circuit is shown below. This simple circuit is very helpful to turn on a relay in place of LED & resistor to connect any appliance or load to operate through it.

The required components of this circuit include input DC supply-6v, 2N222 transistors-2, resistors-330Ω, 200KRΩ & LED-1.

Touch Switch Circuit
Touch Switch Circuit

This circuit can be built with two transistors like a Darlington pair, so it is very responsive. The first transistor in the circuit amplifies the gain & after that, it multiplies with the second transistor. So that high gain can be attained. So due to this high gain, this simple circuit is very responsive to the very small current that activates the LED.

The operating of this circuit can be done with 6V or 9V or 12Volts. If we use 6V then a 330Ω resistor must be used whereas for 9V or 12V, we have to use 390Ω/470Ω resistor correspondingly.

If you use a relay in the circuit in place of LED & resistor after that the same value of relay you have to use like the i/p voltage. A variable resistor with a 200KΩ value is used to regulate the circuit sensitivity.
Once the touchpoints in the circuit are touched, then a small number of current supplies throughout the circuit to activate the LED. The applications of this circuit mainly include lamps, locks, doors & safety boxes.


The key characteristics of 2N2222A are discussed below.

  • The transistor’s completer power should not go above 500mW.
  • The maximum handling frequency capacity is 250MHz.
  • The maximum tolerance is 60V across its two terminals like base & collector.
  • For the 10mA collector current & for 10V, the DC current is approximately 75mA.


The main advantages of using the 2N2222 transistor include the following.

  • This is the most commonly used type of transistor
  • In electronic circuits, most of the switching applications can be done by using this transistor
  • It is capable of handling fairly high magnitude currents as compared to other similar transistors.
  • This transistor switches the load current with 800 mA through it, which is high as compared to others.
  • So this capability will make the device ideal in the applications of linear amplifiers.
  • Small size
  • Less weight
  • Voltage gain is high
  • Low source voltage
  • Low cost
  • Longer life


The main disadvantages of using the 2N2222A transistor include the following.

  • Sensitive
  • Depends on Temperature
  • Input impedance is low
  • Faults cannot be found easily due to small size
  • It is extremely hard to replace with new ones by unsoldering
  • It does not function efficiently like a relay or electrical, mechanical switches.

Where to use/Applications

The applications of the 2N2222A transistor include the following.

  • 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.
  • So, the 2N2222 transistor is the best choice for switching high current loads
  • This kind of transistor is mainly used for amplifying current
  • This transistor can be used as a switch for automatically switch ON/OFF any appliances.
  • It is used for PWM due to its quick response
  • Because of its fast response time, it can be used for pulse width modulation.
  • It is typically used in automation & embedded projects.
  • Audio Preamplifiers
  • Sensor Circuits
  • Audio Amplifier Stages
  • Used to switch several loads simultaneously
  • RF Circuits
  • Darlington Pairs
  • These transistors are used in Motor drive circuits like VFD or variable frequency drives.
  • Used in Rectifier Circuits & DC Inverters
  • It is used as an amplifier to amplify voltage, current & power.
  • Darlington pair transistors are used for attaining the maximum current from the emitter terminal to the collector.

Thus, this is all about an overview of the 2N2222A transistor datasheet. To get the best performance by using this transistor, the user should not use a load above 600mA. The transistor’s CE voltage must be below 40V. An appropriate base resistor can be used to provide the necessary current at the transistor’s base terminal. The transistor should not operate or store under -55o C & above +150o C. Here is a question for you, what are the different types of transistors available in the market?

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