# Transistors 101 ## Overview ![](https://cdn-learn.adafruit.com/assets/assets/000/060/285/medium800/components_Replica-of-first-transistor.jpg?1535484616 Image by Wikipedia user Ulfbastel, CC BY-SA 3.0) At their core, transistors amplify power. Note that: power. You can use a transformer to amplify either current or voltage, but you have to trade off the other. i.e. you can get more voltage but at a lower current, or more current, but at a lower voltage. Transistors can give you an increase in both. This proves to be extremely useful - who _doesn't_ want more power? Transistors are very truly the basis of modern electronics, but we'll be looking at a specific use in this guide: controlling high power circuits/devices with a low power microcontroller. This guide will focus on Bipolar Junction Transistors, aka BJTs. Bipolar because they use two kinds of silicon. Junction because pieces of those two different kinds of silicon are up against each other. - [Next Page](https://learn.adafruit.com/transistors-101/basic-operation.md) ## Featured Products ### TIP120 Power Darlington Transistors - 3 pack [TIP120 Power Darlington Transistors - 3 pack](https://www.adafruit.com/product/976) Transistors are powerful little electronic switches, and when our little NPN transistors aren't power enough for your project, we have been known to use these beefy TIP120 Darlington transistors. Great for whenever you need to control medium to high-power electronics such as motors,... In Stock [Buy Now](https://www.adafruit.com/product/976) [Related Guides to the Product](https://learn.adafruit.com/products/976/guides) ### Bipolar Transistor Kit - 5 x PN2222 NPN and 5 x PN2907 PNP [Bipolar Transistor Kit - 5 x PN2222 NPN and 5 x PN2907 PNP](https://www.adafruit.com/product/3599) Transistors are powerful little electronic switches, and we really like these NPN and PNP transistors whenever we need to control medium-power electronics, such as small motors, solenoids, or IR LEDs. We find them so handy we threw together a mix-and-match bag of PN2222 and PN2907! You... In Stock [Buy Now](https://www.adafruit.com/product/3599) [Related Guides to the Product](https://learn.adafruit.com/products/3599/guides) ### ULN2803: 8 Channel Darlington Driver (Solenoid/Unipolar Stepper) [ULN2803: 8 Channel Darlington Driver (Solenoid/Unipolar Stepper)](https://www.adafruit.com/product/970) Bring in some muscle to your output pins with 8 mighty Darlingtons! This DIP chip contains 8 drivers that can sink 500mA from a 50V supply and has kickback diodes included inside for driving coils. This will let your little microcontroller or microcomputer power solenoids, DC motors (in one... In Stock [Buy Now](https://www.adafruit.com/product/970) [Related Guides to the Product](https://learn.adafruit.com/products/970/guides) ### NPN Bipolar Transistors (PN2222) - 10 pack [NPN Bipolar Transistors (PN2222) - 10 pack](https://www.adafruit.com/product/756) Transistors are powerful little electronic switches, and we really like these NPN transistors whenever we need to control medium-power electronics such as small motors, solenoids, or IR LEDs. We find them so handy, they come in a pack of 10! Each transistor is a general-purpose... In Stock [Buy Now](https://www.adafruit.com/product/756) [Related Guides to the Product](https://learn.adafruit.com/products/756/guides) ### N-channel power MOSFET [N-channel power MOSFET](https://www.adafruit.com/product/355) When you need to switch a lot of power, N-channel MOSFETs are best for the job. These FETs can switch over 60A and 30V and are TO-220 packages so they fit nicely into any breadboard or perfboard. Heat sinking is easy with TO-220's, but because of the very low Rds(on) of down to 0.009 ohms... In Stock [Buy Now](https://www.adafruit.com/product/355) [Related Guides to the Product](https://learn.adafruit.com/products/355/guides) ### Connie the Transistor - Circuit Playground Plushie [Connie the Transistor - Circuit Playground Plushie](https://www.adafruit.com/product/1024) Connie is the co-leader of the group with Cappy. Connie is much more level-headed though, and somewhat of a mother figure for the others, particularly Ruby and Billie. She is very thorough, remarkably smart, and has a good heart. She is very dedicated to the others and acts as a balance to the... No Longer Stocked [Buy Now](https://www.adafruit.com/product/1024) [Related Guides to the Product](https://learn.adafruit.com/products/1024/guides) ### 5V Electromagnet - 2.5 Kg Holding Force [5V Electromagnet - 2.5 Kg Holding Force](https://www.adafruit.com/product/3872) Ever wanted to [feel like Magneto](https://www.youtube.com/watch?v=2VmqIwB11yE)? Well, now you sort-of can! Bring the ferromagnetic objects in the world under your control with an **Electromagnet** The simplest way to make an electromagnet is to get a solenoid,... In Stock [Buy Now](https://www.adafruit.com/product/3872) [Related Guides to the Product](https://learn.adafruit.com/products/3872/guides) ### Mini Push-Pull Solenoid - 5V [Mini Push-Pull Solenoid - 5V](https://www.adafruit.com/product/2776) Solenoids are basically electromagnets: they are made of a coil of copper wire with an armature (a slug of metal) in the middle. When the coil is energized, the slug is pulled into the center of the coil. This makes the solenoid able to pull (from one end) or push (from the other). This... In Stock [Buy Now](https://www.adafruit.com/product/2776) [Related Guides to the Product](https://learn.adafruit.com/products/2776/guides) ## Related Guides - [Hello World of Robotics with Crickit](https://learn.adafruit.com/hello-world-of-robotics-with-crickit.md) - [Make It Bubble](https://learn.adafruit.com/make-it-bubble.md) - [Crickit Harmonic Drawing Machine](https://learn.adafruit.com/crickit-harmonic-drawing-machine.md) - [LEGO Compatible Crickit Rover](https://learn.adafruit.com/lego-compatible-crickit-rover.md) - [Make It Glow With Crickit](https://learn.adafruit.com/make-it-glow-with-crickit.md) - [Motorized Marble Machine](https://learn.adafruit.com/marble-run.md) - [ Adafruit DRV8833 DC/Stepper Motor Driver Breakout Board](https://learn.adafruit.com/adafruit-drv8833-dc-stepper-motor-driver-breakout-board.md) - [Paper Airplane Launcher](https://learn.adafruit.com/paper-airplane-launcher-with-crickit.md) - [Crickit Powered Mini Chair Swing Ride!](https://learn.adafruit.com/mini-chair-swing-ride.md) - [Crickit Collapsible House with MakeCode](https://learn.adafruit.com/collapsible-house.md) - [Improve the Low Speed of Brushed DC Motors](https://learn.adafruit.com/improve-low-speed-performance-of-brushed-dc-motors.md) - [Living Starry Night Painting](https://learn.adafruit.com/animated-starry-night-circuit-playground-express.md) - [Stroboscopic Zoetrope](https://learn.adafruit.com/strobe-zoetrope.md) - [Mount for CRICKIT](https://learn.adafruit.com/mount-for-crickit.md) - [Astrolite NeoPixel Upgrade](https://learn.adafruit.com/astrolite-neopixel-upgrade.md)