
Transistors
Transistors – Components
Transistors are semiconductor devices that are used to amplify or switch electronic signals and electrical power in circuits. They are composed of semiconductor material usually with at least three terminals for connection to an external circuit. When a voltage or current is applied to one pair of their terminals, you can control the current through another pair of terminals. This enables you to control a higher power output with a lower power input signal from something such as a switch or microcontroller.

Do you see the arrow on the emitter? An easy way to remember which round:
- NPN – Not Pointing iN
- PNP – Pointing iN
Bipolar Transistors
A transistor that uses both electrons and electron holes as charge carriers, allowing a small current injected at one of its terminals to control a much larger current flowing between two other terminals, making the device capable of amplification or switching.
Darlington Transistors
Although a Darlington configuration will often act like and look like a standard single transistor, they are actually made up of a pair of transistors.
This multi-transistor configuration known as the Darlington pair is a circuit consisting of two bipolar transistors with the emitter of one connected to the base of the other. This means the current amplified by the first transistor is amplified further by the second! The collectors are connected together.
MOSFET Transistors
The invention of the MOSFET has revolutionised the semiconductor industry. This is due to its compact miniaturisated and mass-produced form factor. This has enabled the creation of high-density ICs such as memory chips and microprocessors. The MOSFET is considered the “workhorse” of the electronics industry.
With next to no input current a MOSFET can control a large load current.
So to summarise, they have faster-switching speeds, a reduced footprint, consume significantly less power, and allow much higher density, compared to BJTs. MOSFETs are also cheaper and have relatively simple production.
We’ve also got some tutorials and projects in our blog that you should check out!
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600 Piece Transistor Kit TO92 Package
Proto-PIC
£12.00Proto-Pic offers the best quality 600 Pieces Transistor Kit. Which is made of top standard materials, our transistor have the high dielectric strength, fast switching speed, large power dissipation and good current performance you need. This assorted...£12.00 -
Transistor - NPN, 2N3904, Common BJT - TO-92
Sparkfun
£0.75Transistor - NPN, 2N3904, Common BJT - TO-92 These are very common, high-quality BJT NPN transistors.Designed for use as general-purpose amplifiers and switches. The useful dynamic range extends to 100mA as a switch and to 100 MHz as an amplifier...£0.75 -
Transistors - NPN, BC547, Bipolar BJT - TO-92
Sparkfun
£0.32Transistors - NPN, BC547, Bipolar BJT - TO-92 These are high-quality BJT NPN transistors that work well with audio applications, switching and amplifying Specifications: Transistor Polarity: NPN Collector-Emitter Voltage V(br)ceo: 45V Transition...£0.32 -
2N2222A NPN Transistor
Proto-PIC
£1.01A basic NPN transistor,2N2222A 0.8A Ic 10Vce.DocumentsDataSheet£1.01 -
Common BJT Transistor - PNP 2N3906
Sparkfun
£0.12These are very common, high quality BJT, PNP transistors made by ST Micro. Datasheet:£0.12 -
TIP120 Darlington NPN 60V 5A TO-220
Proto-PIC
£0.62Nice Darlington Array Transistors are a mainstay of many embedded projects.Use these with your Arduino to turn on Motors, switch on lights and control many other high powered gadgetsDatasheet£0.62 -
MOSFET - N-Channel, 60V, 30A, TO-220
Sparkfun
£1.20MOSFET - N-Channel, 60V, 30A, TO-220 If you’ve ever wondered how to control the headlight of a car from a microcontroller, a MOSFET is what you need.This particular part is a very common MOSFET with very low on-resistance and a control voltage (aka...£1.20 -
IRF520 N-CHANNEL MOSFET
Proto-PIC
£0.60These MOSFETs provide the designer with the best combination of fast switching, ruggedized device design, low on-resistance and cost-effectiveness. FEATURES Dynamic dV/dt Rating Repetitive Avalanche Rated 175 °C Operating Temperature Fast...£0.60 -
2N7000 N-Channel MOSFET
Proto-PIC
£0.50These N-Channel enhancement mode field effect transistors are produced using Fairchild's proprietary, high cell density, DMOS technology. These products have been designed to minimize on-state resistance while provide rugged, reliable, and fast switching...£0.50 -
Power MOSFET STP36NF06 N-Channel 5V Logic Switched
Proto-PIC
£0.60Channel Mode Enhancement Channel Type N Configuration Single Dimensions 10.4 x 4.6 x 9.15mm Height 9.15mm Length 10.4mm Maximum Continuous Drain Current 30 A Maximum Drain Source...£0.60 -
RC Switch with Small Low-Side MOSFET
Pololu
£11.00RC Switch with Small Low-Side MOSFET - Pololu 2802 This RC switch from Pololu converts hobby radio control pulses to digital on/off signals and has an integrated small, low-side MOSFET that allows it to drive small loads (up to around 3 A), such as...£11.00 -
TRIAC - 200V Blocking Voltage
Sparkfun
£1.20Triacs are components that are widely used in AC power control applications, Able to switch high voltages and high levels of current, and over both parts of an AC waveform. This makes these circuits ideal for use in a plethora of applications where power...£1.20