The 2N3906 transistor is a popular PNP bipolar junction transistor used in low power and current, medium voltage applications, and is also widely used in low power amplification and switching. It has two P-type semiconductor materials sandwiched between an N-type semiconductor material. This type of transistor is commonly used as switches and amplifiers because of their ability to control the flow of current and amplify signals.

PNP-type transistors have many important applications in electronic circuits, including audio amplification, power switching, amplification in analog circuits, and logic gates in digital circuits. Specific characteristics of the 2N3906 include its gain, maximum collector current, and maximum collector-emitter voltage.

Ⅰ.Specification parameters of 2N3906

•Configuration:Single
•Transistor polarity:PNP
•Installation style:Through Hole
•Pd-Power dissipation:625 mW
•Maximum DC collector current:200 mA
•Collector-emitter saturation voltage:400 mV
•Emitter-base voltage VEBO:5 V
•Collector-base voltage VCBO:40 V
•Collector-emitter maximum voltage VCEO:40 V
•Gain bandwidth product fT:250 MHz
•Minimum operating temperature:-55℃
•Maximum operating temperature:+150℃
•Current rating:-200mA
•RoHS status:complies with ROHS3 standards
•Number of pins:3
•Number of terminations:3
•Voltage-Rated DC:-40V
•Transition frequency:250 MHz
•hFE minimum value:100
•Transistor element material:silicon

Ⅱ.Working principle of 2N3906

1.Structure: 2N3906 is composed of two P-type semiconductor materials sandwiched between an N-type semiconductor material. This forms two P-N junctions: one between the collector and base, and another between the emitter and base.
2.Polarity: The Base of PNP type BJT is P-type material, the emitter is also P-type material, and the collector is N-type material. This means that in 2N3906, current flows from collector to emitter.
3.When a forward voltage is applied between the base and the emitter, the P-N junction is forward biased, which causes electrons to flow from the base to the emitter while holes flow from the collector to the base. This flow of current causes the current between the collector and emitter (i.e. collector current, ic) to increase. Therefore, 2N3906 can achieve current amplification. This amplification is achieved by controlling the current between the collector and the emitter by adjusting the current between the base and the emitter. This control mechanism makes 2N3906 very useful in electronic circuits because it can convert weak signals into stronger output signals to achieve signal amplification and transmission.
4.Switching function: 2N3906 can also be used as a current switch. When a forward voltage is applied between the base-emitter, the 2N3906 is in a conductive state, allowing current to flow. When reverse voltage or zero voltage is applied, the 2N3906 is in a cut-off state and current cannot flow through it.
5.Amplification function: 2N3906 can be used to amplify weak signals, because a small current flowing into the base can control a larger current collector. The amplification factor is usually determined by the peak amplification factor (hFE or β) of 2N3906.

Ⅲ.Maximum Ratings of 2N3906

Ⅳ.Characteristics of 2N3906

V.Functional characteristics of 2N3906

1.Amplification function: 2N3906 can be used to amplify current, voltage and power. Its peak amplification factor (hFE or beta) is usually between 100 and 1000, depending on the model and operating conditions. This means it amplifies the input signal to produce a larger output signal.

2.Stability: 2N3906 transistor is stable to a certain extent and can work normally within a certain temperature range. However, for high-temperature applications, special attention needs to be paid to its temperature characteristics, because the performance of the triode will be affected by temperature. In a high-temperature environment, the parameters of the 2N3906 transistor may change. For example, the amplification factor may be reduced, the current transmission capability may be weakened, and problems such as thermal breakdown may even occur. Therefore, in high-temperature applications, it is necessary to select a triode that can operate stably in a high-temperature environment, or to take appropriate heat dissipation measures to ensure the stable operation of the triode.

3.Current control: 2N3906 can be used as a current controller. By applying current between the base and the emitter, the current from the collector to the emitter can be controlled. This makes it suitable for applications such as constant current sources, current mirrors, etc.

4.Switching function: 2N3906 can be used as a current switch. When the appropriate voltage is applied between base-emitter, the 2N3906 is in a conductive state, allowing current to flow. When reverse voltage or zero voltage is applied, the 2N3906 is in a cut-off state and current cannot flow through it. This makes it suitable for switching operations in digital logic circuits.

5.Low noise performance: 2N3906 transistors generally have relatively low noise performance, which makes it particularly suitable for applications such as low-noise amplifiers and receivers. In amplification circuits, noise is an important performance indicator. Noise will interfere with signal transmission and cause signal quality to decrease. Therefore, low-noise amplifiers and receivers are very important to improve signal transmission quality and reception sensitivity. The low noise performance of the 2N3906 diode makes it advantageous in these applications. Its noise performance is generally lower than other types of diodes, thus providing clearer signal transmission and higher reception sensitivity.

6.High frequency performance: 2N3906 usually has a relatively high cutoff frequency (ft) and can operate in the range of tens of MHz to hundreds of MHz, making it suitable for high frequency applications such as radio frequency amplifiers.

Ⅵ.2N3906 alternative model

1.2N4403:The 2N4403 is also a PNP bipolar transistor and can replace the 2N3906, especially in low to medium power applications.

2.BC327:BC327 is another common PNP bipolar transistor with similar specifications and performance. It can often be used as a replacement for 2N3906.

3.BC556:BC556 is a PNP bipolar transistor, suitable for some low power and low noise applications, and can be used as a replacement for 2N3906.

4.MPSA42 is a high current PNP bipolar transistor suitable for applications requiring higher current capabilities and can be used as a replacement for 2N3906.

5.S8050:S8050 is another PNP bipolar transistor, usually used in low-power amplification and switching circuits, and can also be considered as a replacement for 2N3906.

Frequently Asked Questions

1.What is the use of 2N3906?
The 2N3906 is a commonly used PNP bipolar junction transistor suitable for general-purpose low-power amplification or switching applications. It is designed for low current, low power and medium voltage and can operate at moderately high speeds. It is complementary to the 2N3904 NPN transistor.

2.How do you test a 2N3906 transistor?
To test a 2N3906 transistor, you can use a multimeter in diode test mode. Connect the positive lead to the emitter, and the negative lead to the base. If it behaves like a diode with a forward voltage drop, it's likely functional. Then, test the reverse leakage current.

3.What is the typical cutoff frequency (ft) for the 2N3906 transistor?
The cutoff frequency (ft) typically falls within the range of tens of MHz to hundreds of MHz, depending on the model and operating conditions.

4.What are the common applications of the 2N3906 transistor?
The 2N3906 transistor is used in signal amplification, switching circuits, and current control applications. It can be found in amplifiers, low-power switching devices, and more.