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2N3906 Transistor Comprehensive Guide-Pin Configurations, Application Scenarios and Equivalents, and How to Test

Catalog

1. Brief Overview of the 2N3906

2. Features and Technical Specifications of 2N3906

3. Pin Configuration and Schematic of the 2N3906

4. Applications of the 2N3906

5. Circuit for 2N3906

6. An example is a switch

7. How to Test the 2N3906

8. 2N3906 vs. BC557

9. Equivalents/Substitutes for the 2N3906

10. Download Datasheet

Brief Overview of the 2N3906

The 2N3906 transistor is well-known for its PNP bipolar junction configuration. It is commonly used in applications requiring low current and power along with moderate voltage levels, such as low-power switching and amplification scenarios. It is designed for operations that require low power consumption and current specifications within a moderate voltage range while maintaining rapid performance standards. This device is packaged in a TO-92 case with a plastic body structure. It has a maximum rated operating current of 200mA, voltage of 40V, and power capacity of 625mW. The collector current of the 2N3906 ranges from 10 μA to 100 mA, adapting to a wide range of current gains from minimal to substantial.

Features and Technical Specifications of 2N3906

- Complementary to the 2N3904/MMBT3904 bipolar transistors
- Collector-Emitter Voltage (VCE): 40V
- Emitter-Base Voltage (VBE): 5V
- Continuous Collector Current (IC): 200mA
- Operating temperature range: -55 to 150°C
- Base Current (IB): Maximum 5mA
- DC Current Gain (hFE): 60
- Enclosed in a To-92 package
- Collector-Base Voltage (VCB): 40V
- Lead-free package options available
- Collector-Emitter Saturation Voltage: 0.25V
- Maximum Power Dissipation: 250mW

Pin Configuration and Schematic of the 2N3906

Pin Number	Pin Name	Description
1	Emitter	Current Drains out through the emitter
2	Base	Controls the biasing of transistor
3	Collector	Current flows in through the collector

Applications of the 2N3906

The 2N3906 is a commonly used PNP transistor, typically employed for high-speed switching and amplifying. It operates in three modes:

Active Region: Here, the 2N3906 acts as an amplifier. The emitter-base junction is forward-biased allowing current to flow from the emitter to the base, whereas the collector-base junction is reverse-biased, which blocks current flow and thus amplifies the signal passing through the transistor.

Saturation Region: In this state, the transistor acts as a closed switch. Both the emitter-base and collector-base junctions are forward-biased. This setup pushes the emitter-base voltage above 5 volts, essentially turning off the current flow and making the transistor non-conductive.

Cutoff Region: Here, the transistor acts as an open switch. Both junctions are reverse-biased, with the emitter-base voltage being less than 5 volts, making the transistor fully conductive. Typically, the base is directly connected to the ground for ease of this configuration.

Common application scenarios for the 2N3906 transistor include:

- High to low current load switching
- Inverters and converter circuits
- Darlington pair circuits
- Alarm systems or dual LED setups
- Low-power amplification circuits
- Flash units
- High-speed switching applications
- General-purpose audio amplifiers
- Suitable for loads with peak voltages up to 40V

Circuit for 2N3906

An example is a switch

In the above diagram, when the switch is closed, the LED will be on, which means that both junctions will be forward biased, and current will flow from the emitter to the collector, and then the LED will emit bright light. Similarly, when the switch is open, both junctions will be reverse-biased and no current will flow from the emitter to the collector, so the LED will be off. A 10kΩ resistor is placed in series with the base to limit the base current.

2N3906 Delay and Rise Time Test Circuitry

2N3906 Storage and Falling Time Equivalent Test Circuit

How to Test the 2N3906

Before starting to test the 2N3906 transistor, ensure you have the following tools:

- Multimeter
- DC power source
- Resistors with known resistance values
- Connecting wires

The testing process for the 2N3906 transistor involves several steps:

Setup Your Equipment:

Configure your multimeter to diode test mode to check semiconductor functionality. Also, connect the DC power supply to appropriate contacts to provide the necessary voltage for testing.

Connect the Transistor:

Properly insert the 2N3906 transistor into a breadboard or test socket, ensuring correct orientation and firm placement, and connect the DC power supply's wires to corresponding transistor pins (emitter, base, collector).

Measure:

Use the multimeter to measure the voltage and resistance across various terminals of the transistor.

Result Analysis:

Compare your obtained values with expected standards to evaluate if the measurements align with the 2N3906 transistor's specifications. Deviations might indicate potential defects or malfunctions within the transistor.

Testing for bipolar devices like the 2N3906 is based on their structure comprising two semiconductor junctions sharing a common terminal (base), similar to a pair of diodes. For PNP transistors (like the 2N3906), the cathodes of these equivalent diodes connect to the base. If both simulated diodes show normal behavior, the transistor is considered to be functioning correctly.

Safety Tips When Using Transistors:

- Avoid operating transistors under conditions exceeding 20V or 700mA to prevent damage.
- Use base resistors of appropriate values to keep the base current within safe limits specified in datasheets or reference materials.
- Do not expose transistors to temperatures above 150°C to avoid thermal damage.

2N3906 vs. BC557

The BC557 transistor is similar to the 2N3906, sharing key characteristics suitable for various applications. The 2N3906 is renowned for its high collector-emitter voltage (VCE), which enables it to efficiently handle higher voltages during operation. Key differences and operational insights include:

High Collector-Emitter Voltage:

The 2N3906 can maintain a high voltage across its collector and emitter terminals, often crucial in circuits requiring high-voltage handling.

Gain Value:

The gain (β) of the 2N3906 is about 300, indicating the transistor's ability to amplify input signals. However, a gain of 300 might not be sufficient for high-power amplifier circuits, which require higher beta values for desired amplification.

Application Limitations:

Due to its gain limitations, the 2N3906 may not be the best choice for high-power amplification tasks, as more potent amplification is needed to effectively drive large outputs.

Equivalents/Substitutes for the 2N3906

2N4403, MPSA13, MPSA92, MPSA55, ZTX555

2N3906 Package

Download Datasheet

Click here to download the STMicroelectronics 2N3906 PDF-Datasheet: STMicroelectronics 2N3906

Frequently Asked Questions [FAQ]

1. What is the difference between 2N3904 and 2N3906?

Both are bipolar transistors, with 3904 being NPN and 3906 being PNP, indicating different schematic symbols and polarity functions.

2. What is the maximum base current of 2N3906?

The maximum base current is 5mA with a Collector Base Voltage of 40V.

3. What is the difference between PNP and NPN?

PNP transistors turn ON by a low signal, whereas NPN transistors turn ON by a high signal. The 'P' in PNP indicates the polarity (positive) at the emitter and the 'N' in NPN indicates the polarity (negative) at the base.

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