2N3906 is a special purpose transistor that has been generally used for low current medium voltage and low power switching as well as amplification, but it is most suitable for high-speed switching. In the market, it is available in the plastic body and TO-92 dip package. Because its collector current range is 10μA to 100mA, therefore, it could be used for low current to high current gain. It is available in the market in a family such as 2N3903G,2N3609RL1, and 2N3906RLRGA, etc. These family members have different characteristics and features which makes it differ from each other.
Pinout Configuration 2N3906
2N3906 is a PNP (positive negative-positive) transistor therefore current flows from emitter to collector. It consists of three pins emitter, base, and collector and these pins are used for a different configuration. Its operating voltage range is -40V dc and pinout configuration with schematic symbol is shown in figure 1,
Figure 1 2N3906 Pinout configuration
|Emitter||Emitter pin is input pin used for basing the emitter base junction|
|Base||Base pin is control pin used for controlling the emitter to collector current.|
|Collector||Collector pin is output pin used for providing current to the load.|
- Type : Bi-polar PNP transistor
- Collector emitter maximum voltage:40V
- Emitter base maximum voltage: 5V
- Collector base maximum voltage: 40V
- Continuous collector current: 200mA
- Junction operating temperature range: -55 to 150C0
- Minimum forward current transfer ratio: 100
- Transition frequency:250MHz
- Maximum collector current: 200mA
- Collector Capacitance: 5pF
- Maximum power dissipation: 250mW
- Storage temperature range: -55 to 150C0
- Collector emitter saturation voltage: 0.25V
- Dc Current gain:60
For further details download datasheet
Where and How to Use 2N3906 Transistor
2N3906 transistor is generally used for high-speed switching and amplification purpose. Either it is used for switching or amplification it works in three modes of operation.
- Active region
- Saturation region
- Cut-off region
In the active region, it works as an amplifier means its emitter-base junction will be forward biased and the collector-base junction will be reversed biased. In the saturation region, it works as close switch means both junctions will be forward biased, and emitter-base voltage will be greater than 5V thus transistor works as a fully closed switch. Similarly, in the cut-off region, it works as an open switch means both junctions will be reverse biased, and emitter-base voltage will be less than 5V thus transistor works as a fully open switch. In this condition, the base is directly connected to the ground.
Example as a switch
Here we will explain how to use a transistor as a switch?
Figure 2 Example of 2N3906 as a switch
According to figure 2, when the switch is closed then LEDs would be on means both junction will be forward biased and current flows from emitter to collector then LEDs will glow brightly. Similarly, when the switch is open then both junction will be reversed biased and no current flows from emitter to collector thus LEDs will be off. 10kΩ resistor is connected in series with the base for limiting the base current.
2N3906 transistor has been widely used in so many real-life applications some of which are,
- Darlington pair transistors
- In flasher and dual LEDs circuits
- High-speed switching applications
- Television and home appliances circuits
- High-frequency inverter and converter circuits
- As a switch for high voltage and low current
- As a switch for high gain and low saturation voltage
- General-purpose audio amplifiers
- Efficient for loads which have peak voltage up to 40V
2D Physical Dimensions
2N3906 transistor is dip type transistor, therefore, it is mounted in a PCB circuit. So during design below physical dimensions are keep in mind. This is according to the datasheet.