BJT & Bipolar Transistors

A Bipolar Transistor or BJT (Bipolar Junction Transistor) is a solid state, three-pin device made from three layers of silicon. A BJT is designed to amplify current, bipolar transistors can also function as a switch. There are two main types of transistor, PNP (positive negative positive) or NPN (negative positive negative).
How a Bipolar transistor is made
A bipolar transistor is made by joining two signal diodes back to back creating two PN junctions connected in series, sharing a common P or N terminal. By nature, silicon does not normally conduct electricity well. However, when silicon is treated with certain chemicals or impurities we can make the material and electrons behave in a different way. This process is called doping. The doping process improves the semiconductors ability to conduct electricity.
What does a bipolar transistor do?
As we said before a bipolar transistor has two possible functions, switching, and amplification. Due to the devices three layers of doped semiconductor material, supplying the transistor with a signal voltage enables the discrete component to act as an insulator or a conductor. This clever change provides the transistors with two basic functions, switching (digital) electronics or amplification (analog) electronics.
Types of transistor
Transistors are available in panel, surface and through hole mounting options in plastic package or metal can versions. All have three terminals or pins, the Base, the Collector, and the Emitter.
Where are bipolar transistors used?
Transistors are one of the most widely used discrete components in electronic designs and circuits. Transistors are used for the amplification of all types of electrical signals in circuits made up of individual components rather than ICs (integrated circuits).

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Description Price PRICED TO CLEAR Transistor Type Maximum DC Collector Current Maximum Collector Emitter Voltage Package Type Mounting Type Maximum Power Dissipation Minimum DC Current Gain Transistor Configuration Maximum Collector Base Voltage Maximum Emitter Base Voltage Maximum Operating Frequency Pin Count Number of Elements per Chip
RS Stock No. 124-1317
Mfr. Part No.2N3904TA
£0.029
Each (On a Reel of 2000)
Units
- NPN 200 mA 40 V TO-92 Through Hole 625 mW 30 Single 60 V 6 V 300 MHz 3 1
RS Stock No. 843-1575
Mfr. Part No.2N3904BU
£0.141
Each (In a Pack of 50)
Units
- NPN 200 mA 40 V TO-92 Through Hole 625 mW 100 Single 60 V 6 V 100 MHz 3 1
RS Stock No. 739-0442
Mfr. Part No.2N3904TA
£0.21
Each (In a Pack of 10)
Units
- NPN 200 mA 40 V TO-92 Through Hole 625 mW 30 Single 60 V 6 V 300 MHz 3 1
RS Stock No. 805-1056
Mfr. Part No.2N3904TFR
£0.061
Each (In a Pack of 200)
Units
- NPN 200 mA 40 V TO-92 Through Hole 625 mW 30 Single 60 V 6 V 300 MHz 3 1
RS Stock No. 842-8015
Mfr. Part No.2N3904BU
£0.033
Each (In a Bag of 1000)
Units
- NPN 200 mA 40 V TO-92 Through Hole 625 mW 100 Single 60 V 6 V 100 MHz 3 1
RS Stock No. 805-1043
Mfr. Part No.2N3904TAR
£0.061
Each (In a Pack of 200)
Units
- NPN 200 mA 40 V TO-92 Through Hole 625 mW 30 Single 60 V 6 V 300 MHz 3 1
RS Stock No. 168-6075
Mfr. Part No.BD139
£0.372
Each (In a Tube of 50)
Units
- NPN 3 A 80 V SOT-32 Through Hole 1.25 W 25 Single 80 V 5 V - 3 1
RS Stock No. 314-1823
Mfr. Part No.BD139
£2.02
Each
Units
- NPN 3 A 80 V SOT-32 Through Hole 1.25 W 25 Single 80 V 5 V - 3 1
RS Stock No. 169-8605
Mfr. Part No.BC33725TFR
£0.038
Each (On a Reel of 2000)
Units
- NPN 800 mA 50 V TO-92 Through Hole 625 mW 100 Single 10 V 5 V 50 MHz 3 1
RS Stock No. 124-1731
Mfr. Part No.BC33725TA
£0.039
Each (On a Reel of 2000)
Units
- NPN 800 mA 45 V TO-92 Through Hole 625 mW 100 Single - 5 V 100 MHz 3 1
RS Stock No. 671-1116
Mfr. Part No.BC33725TA
£0.20
Each (In a Pack of 10)
Units
- NPN 800 mA 45 V TO-92 Through Hole 625 mW 100 Single - 5 V 100 MHz 3 1
RS Stock No. 803-1068
Mfr. Part No.BC33725TAR
£0.048
Each (In a Pack of 200)
Units
- NPN 800 mA 50 V TO-92 Through Hole 625 mW 100 Single 10 V 5 V 50 MHz 3 1
RS Stock No. 178-7544
Mfr. Part No.BC33725TAR
£0.029
Each (In a Bag of 2000)
Units
- - - - - - - - - - - - - -
RS Stock No. 803-1061
Mfr. Part No.BC33725TFR
£0.127
Each (In a Pack of 200)
Units
- NPN 800 mA 50 V TO-92 Through Hole 625 mW 100 Single 10 V 5 V 50 MHz 3 1
RS Stock No. 168-6171
Mfr. Part No.TIP41C
£0.392
Each (In a Tube of 50)
Units
- NPN 6 A 100 V TO-220 Through Hole 65 W 15 Single 100 V 5 V - 3 1
RS Stock No. 485-9812
Mfr. Part No.TIP41C
£0.478
Each (In a Pack of 5)
Units
- NPN 6 A 100 V TO-220 Through Hole 65 W 15 Single 100 V 5 V - 3 1
RS Stock No. 168-6056
Mfr. Part No.TIP35C
£1.254
Each (In a Tube of 30)
Units
- NPN 25 A 100 V TO-247 Through Hole 125 W 10 Single 100 V 5 V 3 MHz 3 1
RS Stock No. 251-3564
Mfr. Part No.TIP35C
£2.02
Each
Units
- NPN 25 A 100 V TO-247 Through Hole 125 W 10 Single 100 V 5 V 3 MHz 3 1
RS Stock No. 103-2964
Mfr. Part No.2N3055G
£3.29
Each (In a Tray of 100)
Units
- NPN 15 A 60 V TO-204AA Through Hole 115 W 5 Single 100 V 7 V 2.5 MHz 2 1
RS Stock No. 545-2210
Mfr. Part No.2N3055G
£4.23
Each
Units
- NPN 15 A 60 V TO-204 Through Hole 115 W 5 Single 100 V 7 V 2.5 MHz 3 1
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