2N3904 Discrete Semiconductor Products

Series:	--
Packaging:	Bulk
Part Status:	Active
Transistor Type:	NPN
Voltage - Collector Emitter Breakdown (Max):	40V
Vce Saturation (Max) @ Ib, Ic:	--
Current - Collector Cutoff (Max):	50nA (ICBO)
DC Current Gain (hFE) (Min) @ Ic, Vce:	100 @ 10mA, 1V
Frequency - Transition:	300MHz
Operating Temperature:	-65°C ~ 150°C (TJ)
Mounting Type:	Through Hole
Package / Case:	TO-226-3, TO-92-3 (TO-226AA)
Supplier Device Package:	TO-92

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Introduction

The 2N3904 is a general-purpose NPN silicon bipolar junction transistor. It is a popularly used device in both digital and analog applications. This small-signal transistor can be used in both switching and linear amplifier stages. It was initially introduced in the 1960s and since then, this transistor has been used in circuits of all sorts. In this article, we will discuss how this transistor is used, how it works and its various application fields.

Section 1: Working Principle

The 2N3904 is an NPN silicon transistor, meaning it is made of three layers of silicon, extrinsically doped with the element phosphorus. The material arrangement makes this device an NPN type, meaning its characteristics such as forward and reverse current, voltage, and power gain are all NPN. It is a bipolar transistor, meaning both conduction and injection of minority carriers occur within the base of the device.The transistor operates in three different regions of operation, namely saturation, cutoff and active regions. In the switching applications, the transistor operates in the saturation and cutoff regions. In the linear applications, the transistor operates in the active region and is able to amplify analog signal with its high current gain or hfe. The base voltage is used to control and manipulate the collector current of the device, thereby controlling the output signal.

Section 2: Applications

The 2N3904 is a versatile transistor and has been used in a number of applications such as audio amplifiers, switching devices, relay drivers, logic gates, negative feedback circuitries, small signal amplifiers and many more. Audio amplifier circuits: In an audio amplifier, the 2N3904 is usually connected in a common emitter configuration, wherein the audio signal is amplified by controlling the collector current of the transistor. Switching devices: The 2N3904 can also be used as a switch, where the base voltage controls the collector current and the device can be switched on and off.Relay drivers: The 2N3904 can be used as a relay driver, wherein the transistor is used to control the on and off state of the relay using the base voltage.Logic gates: The 2N3904 can be used as a logic gate, wherein the transistor is used to create a boolean logic operation.Negative feedback circuitries: The 2N3904 can also be used in a negative feedback circuitry, wherein the transistor is used to create an inverted output signal from the input.Small signal amplifiers: The 2N3904 is ideal for amplifier stages of low power signals because of its high current gain, hfe.

Conclusion

The 2N3904 is a versatile transistor and has been used in a range of application fields. It is a general-purpose transistor and is mostly used for switching and linear amplifier applications. It is an NPN silicon bipolar junction transistor, which operates in three different regions, namely saturation, cutoff and active and is able to deliver high current gain of up to 100. It is an efficient and low-cost transistor, which has been in use since the 1960s and is still popularly used in circuits of all sorts.

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