2N2222A NPN Transistor Features, Technical Parameters, Working Principle, Applications and Usage

Ⅰ. Overview of 2N2222A transistor

Ⅱ. Symbol, footprint and pin configuration of 2N2222A transistor

Ⅲ. What are the features of 2N2222A transistor?

Ⅳ. Technical parameters of 2N2222A transistor

Ⅴ. How does the 2N2222A transistor work?

Ⅵ. Maximum ratings of 2N2222A transistor

Ⅶ. What are the applications of 2N2222A transistor?

Ⅷ. How to use 2N2222A transistor?

2N2222A is a bipolar transistor with high current amplification and low saturation voltage drop, making it widely used in various electronic circuits. This article mainly introduces its pin configuration, features, technical parameters, working principle and applications, which will help you better understand this transistor.

The 2N2222A is a bipolar NPN transistor manufactured by STMicroelectronics. This transistor is primarily designed to operate in the medium voltage range at lower power, medium current and medium speed. Encased in a convenient TO-92 package, this transistor facilitates seamless integration into breadboards and various experimental circuits, promoting accessibility for electronics enthusiasts and professionals alike. This transistor is widely used in power switches, audio amplifiers, power control and wireless communications.

Replacements and equivalents:

• BC549

• BC637

• PN2222

• 2N2222

• 2N2907

• 2N3906

• 2N4403

The symbol, footprint and pin configuration of the 2N2222A transistor are shown in the figure above. Among them, 2N2222A has three pins, their names and descriptions are as follows.

Pin 1 (Emitter): Current drains out through emitter.

Pin 2 (Base): Controls the biasing of transistor

Pin 3 (Collector): Current flows in through collector.

• 2N2222A has lower noise, which helps ensure signal purity.

• 2N2222A has a high amplification factor and can fully amplify the signal, thus improving the sensitivity and performance of the circuit.

• The transistor possesses a significant capacity for driving current and can effectively propel other elements within the circuit.

• The 2N2222A exhibits excellent resistance to high voltage and is capable of enduring substantial voltage fluctuations.

• The 2N2222A has high-speed switching characteristics that allow it to turn on and off quickly, making it ideal for high-speed electronic equipment.

• Manufacturer: STMicroelectronics

• Package / Case: TO-18-3

• Packaging: Bulk

• Length: 5.8mm

• Width: 5.8mm

• Height: 1.5 mm

• Technology: Si

• Transistor Polarity: NPN

• Continuous Collector Current: 600 mA

• Power dissipation: 400 mW

• Operating Temperature: -65°C ~ 175°C

• Mounting Style: Through Hole

• Configuration: Single

• Pin Count: 3

• Part Status: Obsolete

• Product Type: BJTs - Bipolar Transistors

The working principle of 2N2222A mainly involves the forward and reverse bias of the PN junction, and the three working areas of the transistor, namely the amplification area, the cut-off area and the saturation area.

When a forward voltage is applied between the base and emitter, the PN junction in the base region will enter a forward biased state. At this time, the N-type region of the emitter will inject a large number of electrons into the base region, and at the same time, the P-type region of the base will inject a large number of holes into the base region. This injection of electrons and holes will form a weak conductive channel in the base region, called the "minority carrier injection region". In this area, electrons and holes will be reduced in a recombination manner, forming a current amplification effect.

When a forward voltage is applied to the collector and emitter of 2N2222A, and the forward bias voltage between the base and emitter is large enough, the PN junction of the collector will also be forward biased. At this time, the P-type region of the collector will inject a large number of holes into the base region, while the N-type region of the emitter will inject a large number of electrons into the base region. The injection of these electrons and holes will lead to the formation of stronger conductive channels in the base region, which is called a "saturation region." In the saturation region, the ratio of the collector current to the base current of the 2N2222A is controlled. By adjusting the base current, we can achieve precise control of the collector current.

Applying a reverse voltage between the base and emitter of the 2N2222A induces a reverse-biased state in the PN junction within the base region. Consequently, the current flowing between the base and emitter becomes minimal, causing the 2N2222A to transition into the cut-off region. In this state, both the base-emitter current and collector current of the 2N2222A are significantly reduced.

1. Current controller: 2N2222A transistor can be used as a current controller for protection circuit or current control.

2. Switch: 2N2222A can be used as a switch to control the flow of larger current. In digital and analog circuits, it is often used to drive relays and switching power supplies.

3. LED driver: It can be used to drive LEDs and adjust their brightness by controlling the current flowing through them.

4. Amplifier: Using the 2N2222A transistor as an amplifier, the small signal voltage can be converted into a larger output signal. It exhibits stable performance and good accuracy in low power amplifiers. In addition, it is often used in micro oscillators.

5. Switch controller: The 2N2222A transistor serves well as a switch controller, particularly in low-voltage or low-current chip control circuits and low-power signal lights. It is well-suited for applications that demand high reliability and low-power performance.

6. Pulse generator: Due to its fast response speed, it is suitable for building pulse generator circuits.

The diagram below illustrates the circuit for a touch switch using a 2N2222A transistor. This uncomplicated configuration is ideal for activating a relay, offering an alternative to employing an LED and resistor to link any device or load. The necessary components for this circuit encompass a 6V input DC power supply, a 2N2222A transistor, a 330Ω resistor, a 200KΩ adjustable resistor, and an LED.

The circuit can be constructed using two transistors (e.g., a Darlington pair), resulting in a very fast response. The first transistor in the circuit amplifies and gains, and then multiplies with the second transistor. This results in high gain. Therefore, due to this high gain, this simple circuit is very sensitive to very small currents such as activating LEDs.

Operation of this circuit can be accomplished using 6V or 9V or 12Volts. If we use 6V, we must use 330Q resistors. And for 9V or 12V we must use 390Q/470Q resistors. If we use relays instead of LEDs and resistors in the circuit, then we must use the same relay values such as i/p voltage. In addition, we need a 200KΩ variable resistor for adjusting the circuit sensitivity. Once the contacts in the circuit are touched, a small amount of current is supplied throughout the circuit to activate the LEDs. The applications of this circuit mainly include lights, locks, doors and safes.

Frequently Asked Questions

1. 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.

2. What is the difference between 2N2222 and 2N2222A?

The main difference between the two is that the 2N2222A is a higher gain version of the 2N2222. The gain of a transistor is a measure of its amplification ability, and the 2N2222A has a slightly higher gain than the 2N2222, which means it can amplify a signal slightly better.

3. What are the characteristics of transistor 2N2222A?

The 2N2222A is silicon planar epitaxial NPN transistors in Jedec TO-18 metal case. It is designed for high speed switching application at collector current up to 500mA, and feature useful current gain over a wide range of collector current, low leakage currents and low saturation voltage.

4. Where can I find 2N2222A transistor at home?

The old electronics board or damaged electronics board is the main source of a lot of electronic components. So you need to check an old CD, DVD, MP3 player to find a 2n2222A transistor on it.

5. Is 2N2222A silicon?

The CENTRAL SEMICONDUCTOR 2N2221 and 2N2222 are silicon NPN epitaxial planar transistors designed for small signal, general purpose switching applications.