The 2N3906 is a versatile PNP bipolar junction transistor (BJT) widely used in low-power switching and amplification circuits. Manufactured by onsemi, it offers dependable performance with a collector–emitter voltage of 40 V and a collector current of up to 200 mA. This article will discuss the transistor’s features, specifications, working principle, test circuits, and equivalent alternatives.

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What is 2N3906?

The 2N3906 from onsemi is a general-purpose PNP bipolar junction transistor (BJT) designed for low-power switching and amplification. It operates reliably in circuits requiring moderate voltage and current, offering a collector–emitter voltage of 40 V, collector current up to 200 mA, and power dissipation around 625 mW. The transistor comes in a TO-92 package, with a standard pinout configuration of Emitter, Base, and Collector when viewed from the flat face.

This transistor serves as the PNP complement to the 2N3904 NPN transistor, making it ideal for push-pull amplifier stages, signal inverters, and low-current switching applications. It’s frequently used in control systems, LED drivers, and analog signal processing circuits. Its wide availability and dependable performance make it a staple in both educational and industrial electronic projects.

If you are interested in purchasing the 2N3906, feel free to contact us for pricing and availability.

2N3906 Symbol

2N3906 Pin Configuration

2N3906 CAD Model

2N3906 Equivalent Test Circuit

The figures below show the 2N3906 transistor test circuits used to measure switching performance - specifically, delay, rise time, storage time, and fall time.

In the Delay and Rise Time Equivalent Test Circuit, the 2N3906 is tested as a switching device. A pulse signal passes through a 10 kΩ resistor into the base, turning the transistor on and off. The circuit uses a 3 V collector supply with a 275 Ω load resistor and a total shunt capacitance under 4 pF. This setup measures how quickly the transistor responds (delay) and how fast the output voltage rises when switching from off to on.

In the Storage and Fall Time Equivalent Test Circuit, an additional 1N916 diode is added between the base and emitter. This helps discharge stored charge carriers faster when the transistor turns off, allowing accurate measurement of storage and fall times. The test evaluates how quickly the transistor stops conducting and how sharply the output voltage falls, reflecting its switching efficiency.

2N3906 Typical Transient Characteristics

The 2N3906 Typical Transient Characteristics graph illustrates the transistor’s behavior in terms of capacitance and charge response under varying conditions.

In the Capacitance graph (left), the input (Cibo) and output (Cobo) capacitances decrease as the reverse bias voltage increases. This means that as voltage rises, the depletion region inside the transistor widens, reducing capacitance. The curves for 25°C and 125°C show that temperature slightly affects capacitance, but the variation remains minimal - indicating stable performance across temperature changes.

In the Charge Data graph (right), the total charge (QT) and accumulated charge (QA) rise with higher collector current (IC). The transistor stores more charge at higher operating currents, which can influence its switching speed. The higher curve at 125°C shows that charge storage increases with temperature, causing slower switching at elevated thermal conditions.

2N3906 Features

• Collector-Emitter Voltage (Vce): 40 V maximum, suitable for medium-voltage circuits.

• Collector Current (Ic): 200 mA continuous current for low-power applications.

• Power Dissipation (Pd): Up to 625 mW at 25°C, ensuring stable performance.

• Operating Temperature: Works efficiently from -55°C to +150°C.

• DC Current Gain (hFE): 60 to 300, providing consistent amplification.

• Transition Frequency (fT): 250 MHz, ideal for high-speed switching and RF signals.

• Collector-Emitter Saturation Voltage (V_ce(sat)): 0.25 V typical, ensuring efficient current flow.

• Collector Capacitance (Cobo): Around 5 pF, minimizing signal distortion.

• Thermal Resistance (RθJA): About 200°C/W, allowing effective heat dissipation.

• Switching Speed: Rise and fall times around 35 ns for fast digital operations.

• Charge Response: As collector current increases, total and accumulated charge rise predictably, maintaining stable switching performance.

• Capacitance Behavior: Input and output capacitance decrease with higher reverse bias voltage, ensuring reliable frequency response.

• Package Type: TO-92, through-hole design for easy mounting and testing.

• Polarity: PNP, conducting when base voltage is lower than the emitter.

• Complementary Pair: Works with the 2N3904 for balanced circuit designs.

• Noise Figure: About 4 dB, providing clean and accurate signal amplification.