Anything in the 1K to 50K range will work fine.Ĭonnect the TIP120 circuit to one of the PWM output pins. The value is not important as it is just being used as a voltage divider and does not need to supply much current. The circuit shown here uses a potentiometer to provide a variable input and a TIP120 transistor to create a variable PWM output that can be used to drive fans and small motors at variable speeds by simply adjusting the potentiometer.Ĭonnect the wiper output of the potentiometer to the A0 analog input with the ends connected to VCC (3.3 or 5V depending on the MCU) and ground. It is our go-to for higher power NPN transistor applications that we want to drive directly off an MCU pin. While the TIP120 is considered a bit old-school, it’s a good workhorse transistor for many applications, can handle a fair amount of power and is inexpensive. If using with an MCU, it is possible to drive the transistor directly from an output pin using a series resistor to limit current to safe levels. These are good for general purpose amplification and slower speed switching and are frequently used for driving motors, fans, high power LEDs and similar applications. They can be used when you need to step up to an NPN transistor with more grunt than something like a PN2222 can deliver but don’t really need a big MOSFET. This gives the transistor a much larger current gain which is useful in applications where current amplification or switching is required. The Darlington transistor architecture is actually composed of 2 transistors in an emitter-base follower configuration along with associated resistors in a single package with a BCE pin-out. They are good for up to 60V with a constant current of 5A or up to 8A peak. These TIP120 NPN Darlington power transistors let you control quite a bit of power.
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