Part number: 2N3904                     


Introduction:

2N3904 is an NPN transistor which is used for general purpose including switching and amplification. It has three terminals Emitter, Base and Collector. It is a type of Bipolar Junction Transistor BJT as it is a current-controlled transistor. In 2N3904, when the base pin is grounded the emitter and collector will be opened which is known as reverse-biased while the emitter and collector will be closed when the signals will be transferred to the base pin this is known as forward biased.

2N3904 Pin Configuration

Pin #

Pin Name

Working

1

Emitter

Current moves out through emitter

2

Base

Controls the biasing of transistor

3

Collector

Current moves in through collector


The amplification capacity of the transistor is determined by the gain value of NPN transistor which is 300 for 2N3904. The maximum amount of current which can flow through collector pin is 200mA. Thus we can not use this transistor for loads which consumes more than 200mA. We have to supply current to the base pin to bias the transistor and this current value should be restricted to 5mA.

When transistor is being used as a switch it operates in two modes; cut off region and saturation region. When the transformer is wholly biased it allows full current to pass through emitter and collector that is 200mA. This mode is called a saturation region.  When the current through the base is removed, the transistors are fully off at that time this mode is called as cut off region. When it acts as a switch, maximum current it can support is 100mA while acting as an amplifier, the maximum frequency it can support is 100Mhz.


Voltage/Current Rating :

Parameters

Values

Units

Transistor type

Bipolar Junction Transistor BJT

 --

BJT Type

NPN

 --

Voltage Max.

40

 V

Current Max.

200

 mA


 2N3904 NPN Specifications and Features  参数

  • Bipolar NPN transistor
  • 2N3904 usually used for the purpose of amplification and fast switching
  • Maximum Collector Current (Ic) 200mA
  • Maximum Collector-Emitter Voltage (Vce) 40V
  • Maximum Collector-Base Voltage (Vcb) 60V
  • Maximum Emitter-Base Voltage (VEBO) 6V
  • Operating Temperature (To) -55 to 155 C

 

2N3904 as Switch

When a transistor is working as a switch, it works on two modes saturation region and cut off the region as explained earlier. When we provide the required amount of current at the base pin, the transistor will be an open switch when it is forward biased and it will e a closed switch when it is reverse biased. The current at the base pin should me 5mA maximum more than it will destroy the transistor. This is why a resistor is connected in series with the base pin. This resistor value can be calculated as

                                                                                      RB =  VBE  /  IB

 2N3904 as Amplifier

The transistor can amplify the power, current and voltage at different configurations. It acts as amplifier while operating in  an active region. The configurations used in the amplifier circuit are

● Common Emitter Amplifier ● Common Base Amplifier ● Common Collector Amplifier

When it is acting as an amplifier, the DC gain of the transistor can be calculated by the following formula;

        DC...

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