2N3906 Transistor

2N3906 Transistor

The 2N3906 is a popular PNP bipolar junction transistor (BJT) used for general-purpose low-power amplification and switching applications. It is commonly paired with the 2N3904 NPN transistor and is known for its reliability, affordability, and availability.

General Information

• Type: PNP Bipolar Junction Transistor
• Application: General-purpose, switching, and amplification
• Packaging: TO-92 (plastic)

Key Features

• Complementary to the 2N3904 (NPN)
• Low saturation voltage
• Fast switching speed
• Suitable for a wide range of analog and digital applications

Specifications

Parameter	Symbol	Value
Maximum Collector-Emitter Voltage	VCEO	–40 V
Maximum Collector-Base Voltage	VCBO	–40 V
Maximum Emitter-Base Voltage	VEBO	–5 V
Maximum Collector Current	IC	–200 mA
Power Dissipation	Ptot	625 mW
Transition Frequency	fT	250 MHz
DC Current Gain (hFE)	hFE	100–300

Pin Configuration

The 2N3906 transistor has three pins in the TO-92 package:

• Pin 1: Emitter
• Pin 2: Base
• Pin 3: Collector

(Note: Viewed with flat side facing you.)

Applications

The 2N3906 is commonly used in:

• Low-power signal amplification
• General-purpose switching
• Analog circuits
• Complementary push-pull amplifier designs (with 2N3904)
• LED control circuits

Circuit Example

Basic PNP Switching Circuit A 2N3906 can be used to switch a load:

• Connect the emitter to the positive voltage supply.
• Connect the collector to one end of the load; the other end of the load goes to ground.
• A base resistor is connected between the base and ground (or a logic signal).
• When the base is pulled low (below the emitter potential by ~0.7 V), the transistor turns on.

Advantages

• Low cost and widely available
• Ideal for negative-side switching
• Fast switching response
• Useful in complementary pair configurations

Limitations

• Limited to low-current applications
• Not suitable for high-voltage or high-power loads

Common Alternatives

• PN2907 (higher current rating)
• BC558 (European equivalent)
• 2N2906

Complementary Pair

• The 2N3906 is the PNP complement of the NPN 2N3904.

Additional Resources

• Bipolar Junction Transistor - Wikipedia
• 2N3906 Datasheet