Hello friends! Welcome back to ElectroDuino. Hope you all are doing well. This blog is based on the 2N2222A Transistor – Pin Diagram, Specifications & Working Principle. Here we will discuss the Introduction to the 2N2222A transistor, Pin diagram, How it Works, Specification, Features, Equivalent, Applications, and Download Datasheet.
Like every other amplifier, even a 2N2222A transistor is also used for amplification and switching. It is a common NPN Bipolar Junction Transistor i.e., one P-doped layer stands between the two N-doped layers. Since it’s an NPN transistor so the collector and emitter are reverse biased and the base is forward biased. It is a current controlled transistor, specially outlined to have fairly high speed even in low power, low to medium current, and medium voltage. It is accessible in the package of To-92.
It also offers a constant DC collector current like 800 mA. Therefore, when the 2N2222A transistor is fully biased, then it allows a maximum of 800 mA current to flow across the collector emitter. Hence, we can say that it is ideal for applications that require low to medium current. It is commonly used in very high-frequency amplifiers.
2N2222A Transistor Pin Configuration/Pin diagram/Pinout
It consists of three terminals namely, collector, base, and emitter. The pin configuration/pin diagram and functionality of the 2N2222A Transistor are shown below.
|This pin allows the current to enter the transistor form here.
|This pin controls the biasing of the transistor.
|This pin allows the current to come out of the transistor.
Working Principle of 2N2222A Transistor
As mentioned earlier, in the 2N2222A transistor, the dopped layer is embedded between two n-dopped layers. The collector and emitter are left open when the base pin is held at the ground and are closed when a signal is provided to the base pin. 2N2222A has a gain value of 110 to 800; which determines its amplification value. The 2N2222A transistor offers a constant DC collector current of 800 mA, so, loads that consume more than 800 mA current cannot be connected using this transistor.
For biasing current is supplied to the base pin (IB) which should be under 5 mA. After it gets fully biased then it can allow a maximum of the max value of current flows across the collector and emitter. This particular stage is called Saturation Region at this time the voltage allowed across the collector-emitter (VCE) and base-emitter (VBE) could be 200 and 900 mV respectively.
When the base current is removed the transistor gets fully off, and this stage is called as the Cut-off Region. At Cut-off Region the VBE remains be around 660 mV.
How to use 2N2222A Transistor
The 2N2222A transistors have a large use in the world of switches and amplifiers – the two main uses of any transistor existing in the electronics arena.
Firstly, we will talk about,
2N2222A Transistor as a Switch
Transistors are most commonly used as a switch in the electronic world.
When a voltage difference is applied to the base, a current flow across the collector-emitter (ICE), and the switch is turned off when there is no base voltage. The VCE is almost equal to zero when a sufficient voltage i.e., VIN > o.7 is applied between base and emitter. When the VIN is zero the transistor works in the cut-off region and acts as an open circuit.
For example, when sufficient positive voltage (+V) is applied at the base terminal of the transistor, then the transistor is turned on and acts as a closed switch, so the current flows from the source (+5v) to the ground through the load (LED). As a result, LED starts glowing.
When No Voltage (0V or Ground) is applied at the base terminal of the transistor, then the transistor is turned off and acts as an open switch, so the current can’t flow from the source (+5v) to the ground through the load (LED). As a result, LED is turned off.
We need to connect a resistor between the power source and base terminal, that will limit the current flowing through the transistor to prevent it from damaging. The value of the resistor can be determined using the following formula
RB = VBE / IB
2N2222A Transistor as an Amplifier
As previously mentioned, the 2N2222A transistor can also function as an amplifier. An amplifier circuit is used to increase the amplitude of a signal. The input of an amplifier is either a voltage or a current, and its output is an amplified version of the input signal. It means the transistor receives a weak signal as input through the base junction and produces the amplified signal as output through the collector. This transistor may use different configurations namely Common collector, Common base, and Common emitter to amplify the incoming signals whether it is current, voltage, or power. Bur, the most commonly used configuration is common-emitter.
For the 2N2222A transistor to work as an amplifier it is designed in such a way that the input would always be applied at the forward-biased junction and the output would be collected across the reverse-biased junction. In the common-base configuration, the gain is less than 1 and in the common collector configuration, the gain is almost equivalent to 1.
Specifications and Features
In the technical world, the 2N2222A transistor consists of many amazing features and specifications which makes it really useful as an electronic component. A few specifications and features are listed below;
- Polarity – NPN
- Termination type – through holes
- VCE – 50 V once the base terminal is open
- VEB – 6 V once the collector terminal is open
- VCB – 75 V once the emitter terminal is open
- DC collector current – 800 mA
- DC current gain – 100
- Total dissipation power – 1 W
- IB – 5 mA
- Input capacitance – 25 pF
- Output capacitance – 8 pF
- Fall time – 60 ns
- Turn on time – 25 ns
The transistors that can be used in the place of 2N2222A transistors are 2N3055, 2N3906, 2N3904, 2SC5200, BC636, BC696, etc.
The advantages of using the 2N2222A transistor are mentioned below;
- It can handle a high magnitude of currents.
- It is ideal for the application of linear amplifiers.
- It is small in size and has less weight.
- Voltage gain is high.
- The low source voltage is used.
- Cost is comparatively lower.
- It is having quite a long life.
Even though 2N2222A transistors have a lot of pros but it also consists of some cons;
- It is very sensitive.
- It is temperature-dependent.
- Its input impedance is low.
- It gets difficult to find its faults due to small size.
- Efficiency is low.
The applications of the 2N2222A transistor are mentioned as follows;
- Used to amplify voltage, current, and power.
- Used in Rectifier Circuits and DC Inverters.
- Used in Motor drives like variable frequency drive (VFD).
- Use to switch several types of loads.
- These are also used in Darlington Pairs.
- They have numerous use in sensor circuits and audio preamplifiers.
- It can also be used for pulse width modulation.