How to use a Transistor as a Switch Circuit Diagram Figure 7 shows the basic circuit for using a transistor to control a high-current load. You connect a DC power source to one terminal of the load, then connect the second terminal of the load to the collector of the transistor (or drain, for a MOSFET) of the transistor. If this type of switching arrangement is acceptable, then the low-side switch is usually the cheapest way to achieve load switching. BJT Low-Side Switch A BJT can be used as a load switch and come in two flavors: NPN and PNP. For low-side switching, NPN transistors are used, and for high-side switching a PNP is used.
For the transistor to operate as a switch, a principle of the small base current controlling the large collector load current is used. If you want to control large currents, use the Darlington transistor as a switch If we want to connect a load that requires a higher operating current demand of more than 3mA, it will burn the microcontroller. Many output devices will require a transistor switching circuit to operate a high current requirement load, such as relays, solenoids, and motors. How to use it? Here's how to set up both the BJT and the MOSFET transistor as a switch so you can easily control things like motors, lamps, and more.
How to Use Transistors (BJTs) as ON/OFF Switch Circuit Diagram
Introduction Transistors are often used as electronic switches, to control loads which require high voltage and current from a lower voltage and current. The most common example you'll see of this in a physical computing class is to use an output pin of a microcontroller to turn on a motor or other high current device. These pins are meant to send control signals, not to act as power supplies. The most common way to control another direct current device from a microcontroller is to use a transistor. Transistors allow you to control the flow of a high-current circuit from a low-current source. Video: Transistor Schematics Video: Meet the motors
Electronics Tutorial about the Transistor as a Switch and using the Transistor as a Switch to operate relays, motors, lamps and other such loads
