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Complete Guide to the 2N3906 PNP Transistor

The 2N3906 transistor is a popular PNP transistor used in simple amplifying and switching circuits. This guide covers its features, uses, pin layout, and practical applications to help you understand its role in various electronic projects.

Catalog

Overview of 2N3906 Transistor

The 2N3906 is a commonly used PNP transistor that serves well in low-power amplification and switching tasks. Designed to handle moderate voltage levels and small currents, it operates by toggling the collector and emitter junctions between open and closed states depending on the base pin's voltage. When the base pin is grounded, the transistor is in a forward-biased state, allowing current to flow from the emitter to the collector. When a signal is applied to the base, it goes into a reverse-biased state, stopping current flow.

With a gain value between 110 and 300, this transistor can effectively amplify small signals. However, it has a current limit on its collector, so it’s best suited for applications where the current requirement stays under 200mA. The 2N3906 has two main operational states: saturation, where the transistor is fully on, allowing maximum current flow, and cutoff, where it’s entirely off with no current between the emitter and collector. These properties make it versatile for many general-purpose applications, whether in basic amplifiers or simple switch circuits.

Pin Layout for 2N3906 Transistor

Pin Configuration

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

2N3906 CAD Model

2N3906 Symbol

2N3906 Footprint

2N3906 3D Model

Key Features of 2N3906 Transistor

PNP Transistor Design

The 2N3906 is a PNP transistor, meaning it conducts current when its base is at a lower voltage than the emitter. This design allows it to control current flow effectively in low-power circuits where this type of polarity is needed.

High DC Current Gain

With a DC current gain (hFE) of up to 300, the 2N3906 can amplify small base currents to produce larger collector currents. This feature makes it a good choice for applications requiring moderate signal amplification.

Moderate Current Handling

The transistor can handle a continuous collector current of 200mA. This capacity enables it to control low-power devices without overheating or needing additional cooling measures, provided that the current remains within its safe range.

Emitter-Base Voltage

An emitter-base voltage (VBE) of 5V means that the 2N3906 can manage circuits with a reasonable voltage range, making it suitable for typical low-voltage applications without requiring complex adjustments.

Compact To-92 Package

The 2N3906 is available in a TO-92 package, which is small and convenient for use on breadboards and in compact circuits. This makes it easy to integrate into projects where space is limited.

2N3906 Transistor Specifications

Technical specifications, features, characteristics, and components with comparable specifications of ON Semiconductor 2N3906BU.

Type	Parameter
Lifecycle Status	ACTIVE (Last Updated: 2 days ago)
Factory Lead Time	6 Weeks
Mount	Through Hole
Mounting Type	Through Hole
Package / Case	TO-226-3, TO-92-3 (TO-226AA)
Number of Pins	3
Weight	179mg
Transistor Element Material	SILICON
Collector-Emitter Breakdown Voltage	40V
Number of Elements	1
hFEMin	100
Operating Temperature	-55°C~150°C TJ
Packaging	Bulk
Published	2007
JESD-609 Code	e3
Pbfree Code	yes
Part Status	Active
Moisture Sensitivity Level (MSL)	1 (Unlimited)
Number of Terminations	3
ECCN Code	EAR99
Terminal Finish	Tin (Sn)
Voltage - Rated DC	-40V
Max Power Dissipation	625mW
Terminal Position	BOTTOM
Current Rating	-200mA
Frequency	250MHz
Base Part Number	2N3906
Element Configuration	Single
Power Dissipation	625mW
Transistor Application	SWITCHING
Gain Bandwidth Product	250MHz
Polarity/Channel Type	PNP
Transistor Type	PNP
Collector Emitter Voltage (VCEO)	40V
Max Collector Current	200mA
DC Current Gain (hFE) (Min) @ Ic, Vce	100 @ 10mA 1V
Vce Saturation (Max) @ Ib, Ic	400mV @ 5mA, 50mA
Transition Frequency	250MHz
Collector Base Voltage (VCBO)	-40V
Emitter Base Voltage (VEBO)	-5V
Turn On Time-Max (ton)	70ns
Height	5.33mm
Length	5.2mm
Width	4.19mm
REACH SVHC	No SVHC
Radiation Hardening	No
RoHS Status	ROHS3 Compliant
Lead Free	Lead Free

Circuit Applications of 2N3906

Delay and Rise Time Equivalent Test Circuit

Storage and Fall Time Equivalent Test Circuit

Equivalents of 2N3906 Transistor

Model Number	Manufacturer	Description
2N3906D26Z	Fairchild Semiconductor Corporation	Small Signal Bipolar Transistor, 0.2A I(C), 40V V(BR)CEO, 1-Element, PNP, Silicon, TO-92
2N3906D27Z	Fairchild Semiconductor Corporation	Small Signal Bipolar Transistor, 0.2A I(C), 40V V(BR)CEO, 1-Element, PNP, Silicon, TO-92
2N3906RLRMG	On Semiconductor	Small Signal PNP Bipolar Transistor, TO-92 40 V, 0.2 A, TO-92 (TO-226) 5.33mm Body Height, 2000-FNFLD
2N3906RLRA	Motorola Semiconductor Products	Small Signal Bipolar Transistor, 0.2A I(C), 40V V(BR)CEO, 1-Element, PNP, Silicon, TO-92
2N3906AMO	NXP Semiconductors	TRANSISTOR 200 mA, 40 V, PNP, Si, SMALL SIGNAL TRANSISTOR, TO-92, BIP General Purpose Small Signal
2N3906RLRPG	Rochester Electronics LLC	200mA, 40V, PNP, Si, SMALL SIGNAL TRANSISTOR, TO-92, CASE 29-11, TO-226, 3 PIN
2N3906G	Micro Commercial Components	Small Signal Bipolar Transistor, 0.2A I(C), 40V V(BR)CEO, 1-Element, PNP, Silicon, TO-92, PLASTIC PACKAGE-3
2N3906TA	On Semiconductor	200 mA, 40 V PNP Small Signal Bipolar Junction Transistor, 2000-FNFLD
2N3906STOB	Zetex / Diodes Inc	Small Signal Bipolar Transistor, 0.2A I(C), 40V V(BR)CEO, 1-Element, PNP, Silicon, TO-92 STYLE, E-LINE PACKAGE-3

Alternative Options for 2N3906

• BC157

• BC558

• 2SA1943

• BD140

• S8550

• TIP127

• TIP42

Functionality of 2N3906 in a PNP Circuit

In a basic PNP circuit using the 2N3906, the transistor typically functions as either a switch or an amplifier. To operate as a switch, the emitter is connected to a positive voltage source, such as +3V, while a pushbutton switch is placed at the base. With the button unpressed, no current flows to the base, keeping the transistor in an "on" state by default. This configuration allows current to flow through to the collector, powering any connected component, such as an LED.

When the button is pressed, the voltage at the base becomes greater than that at the emitter, which blocks current flow between the emitter and collector, effectively switching off any connected component. This setup demonstrates the core principle of a PNP transistor: it remains in an "on" state as long as the base voltage is lower than the emitter. When the base voltage exceeds the emitter, it blocks current flow, thus turning the circuit "off."

Uses of 2N3906 Transistor

The 2N3906 is widely applicable for switching and amplification tasks. Its structure makes it ideal for switching high-voltage, low-current loads, especially when working within its 200mA current limit. It can be used in circuits where consistent, low-level amplification is needed, though its gain limit means it isn’t suited for heavy-duty amplifying. Due to its PNP nature, it’s often chosen when reverse-polarity configurations are required, making it versatile for various low-power applications, including signal control, LED circuits, and low-current motor drivers.

Guide to Operating the 2N3906 as a Switch

Operating the 2N3906 as a switch is straightforward. In a standard PNP configuration, the transistor is usually "on" when the base pin is grounded. This default "on" state allows current to flow from the emitter to the collector. To turn the switch "off," a voltage source is applied to the base pin, which prevents current from flowing between the emitter and collector. This design helps with controlling small loads without requiring complex setup.

To protect the transistor in switch mode, it’s common to place a resistor between the base and the controlling input, calculated using the formula RB = VBE / IB. This resistor ensures that the current flowing to the base pin remains within safe limits, preventing any potential damage to the transistor. When configured with this resistor, the 2N3906 can reliably control a range of low-current devices, such as small motors or LEDs.

Parts with Similar Specifications to 2N3906 Transistor

The parts on the right have specifications similar to the ON Semiconductor 2N3906BU.

Manufacturer	2N3906BU	2N3906TA	2N3906TFR
ON Semiconductor	Through Hole	Through Hole	Through Hole
Package / Case	TO-226-3, TO-92-3	TO-226-3, TO-92-3 (TO-226AA)	TO-226-3, TO-92-3 (TO-226AA)
Collector Emitter B.	40 V	40 V	40 V
Max Collector Curr.	200 mA	200 mA	200 mA
Transition Frequency	250 MHz	250 MHz	250 MHz
Collector Emitter S.	-400 mV	-400 mV	-250 mV
hFE Min	100	100	100
Max Power Dissipa.	625 mW	625 mW	625 mW

Applications of 2N3906 Transistor

Low-Power Switching

The 2N3906 is commonly used for switching low-current, high-voltage loads. It’s ideal for circuits where you need a reliable switch that doesn’t draw much power, such as LED arrays or simple relay controls.

Signal Amplification

Its moderate gain allows it to amplify signals in low-power audio circuits and other small amplification setups. While it’s not suitable for high-power amplification, it’s a great fit for smaller, consistent signal boosts.

Inverter and Converter Circuits

The PNP design makes the 2N3906 useful in inverter and converter circuits, particularly where current direction control is needed. It can be set up to switch currents, supporting conversion functions in simple power management designs.

Dual LED or Lamp Flasher

The transistor can also be used in circuits designed to flash LEDs or lamps. By controlling current flow based on the input signal, it creates a simple flasher effect, useful in indicator lights or warning signals.

Darlington Pair Configurations

For applications needing higher gain, the 2N3906 can be paired with another transistor in a Darlington configuration. This setup amplifies current even further, making it possible to drive slightly larger loads while maintaining good performance.

2N3906 Package Types

TO-92 (Bulk)

TO-92 (Ammo, Tape, and Reel)

Marking Diagram for 2N3906 Transistor

About the Manufacturer of 2N3906

ON Semiconductor, a widely respected manufacturer, focuses on providing efficient power and signal management solutions. Their products, including the 2N3906, are designed to meet the needs of a broad range of applications, from automotive and communications to computing, consumer electronics, and industrial systems. Known for their innovation and commitment to quality, ON Semiconductor offers reliable components that are used by engineers and designers worldwide to create effective, sustainable solutions. Their focus on power efficiency helps support environmentally friendly and energy-saving projects across multiple industries.

Datasheet PDF

2N3906TA Datasheet:

2N3906TA.pdf

2N3906BU Datasheet:

2N3906BU.pdf

2N3906TA Datasheet:

2N3906TA.pdf

2N3906TFR Datasheet:

2N3906TFR.pdf