Free pinout pictures
Transistor and regulator pinouts
Which leg is which on nineteen parts from beginner kits, read from each maker's datasheet. Every page has a picture to download, the key ratings, a first circuit and the usual questions answered.
Pin 1 is the left leg. Hold a small transistor with its flat face toward you, or a TO-220 part with its printed face toward you, legs pointing down. Then count 1, 2, 3 from the left.
Check your part before wiring. Read the maker and the full part number printed on it, open that maker's datasheet, or test the legs with a multimeter's diode setting.
Small transistors (TO-92)
BC547NPN transistorC-B-EThe small NPN transistor in most beginner kits: switches LEDs, buzzers and small relays up to 100 mA.
BC557PNP transistorC-B-EThe PNP partner of the BC547: switches the plus side of small loads up to 100 mA.
BC337NPN transistorC-B-EA small NPN with a big current rating: up to 800 mA in a TO-92 case, for LED strips, relays and small motors.
BC327PNP transistorC-B-EThe PNP partner of the BC337: up to 800 mA in a TO-92 case, for switching the plus side of LED strips, relays and small loads.
2N2222ANPN transistorE-B-CThe classic general-purpose NPN for currents up to about 500 mA: relays, small motors, LED groups.
2N3904NPN transistorE-B-CA general-purpose NPN up to 200 mA, popular in US kits and Arduino starter sets.
2N3906PNP transistorE-B-CThe PNP partner of the 2N3904, for switching the plus side of loads up to 200 mA.
S8050NPN transistorE-B-CA low-voltage NPN for up to 0.5 A, common in kits and on cheap modules.
S8550PNP transistorE-B-CThe PNP partner of the S8050: switches the plus side of loads up to 0.5 A at low voltage.
2N7000N-channel MOSFETS-G-DA small N-channel MOSFET in a TO-92 case: a 5 V pin switches LEDs and small relays up to 200 mA, with no base current.
Power transistors and MOSFETs (TO-220)
TIP31CNPN power transistorB-C-EA 3 A, 100 V NPN power transistor in TO-220, for lamps, small motors and simple amplifiers.
TIP120NPN Darlington transistorB-C-ETwo transistors in one TO-220 case: a few mA from an Arduino pin switches up to 5 A.
IRFZ44NN-channel MOSFETG-D-SA 55 V N-channel power MOSFET with very low on-resistance, for motors, LED strips and heaters.
IRLZ44NLogic-level N-channel MOSFETG-D-SThe logic-level twin of the IRFZ44N: a 5 V Arduino pin turns it fully on, for LED strips, motors and heaters.
IRF540NN-channel MOSFETG-D-SA 100 V N-channel power MOSFET for motors and lamps on 12 V to 48 V supplies; it needs about 10 V on its gate.
Voltage regulators (TO-220)
78055 V voltage regulatorIN-GND-OUTThe classic fixed 5 V regulator: 7.5 V to 35 V in, a steady 5 V out, and 1 A to 1.5 A depending on the maker.
781212 V voltage regulatorIN-GND-OUTThe 12 V member of the 78xx family: about 14.5 V to 35 V in, a steady 12 V out, up to 1 A to 1.5 A depending on the maker.
7905−5 V negative voltage regulatorGND-IN-OUTThe negative twin of the 7805: about −7 V to −25 V in, a steady −5 V out. Its legs are in another order and its tab is the input, not ground.
LM317Adjustable voltage regulatorADJ-OUT-INAn adjustable regulator: two resistors set any output from 1.25 V to 37 V, up to 1.5 A.
Try one first
Wire a transistor and watch it switch
The wiring board has the BC547, BC557, PN2222A, TIP120 and IRFZ44N. Join them with wires and watch the circuit work before you build it for real.
Open the wiring board