Then, the transistor becomes a closed switch and allows the maximum current to flow through the circuit.Īdditionally, there is an easy way to switch any amount of power from moderate to high.Īll you’ve to do is connect the emitter terminal of the transistor directly to the ground and pair the transistor with an open-collector output. When you apply a positive signal to the base, it sets the transistor to ON mode. Once it’s off, it serves as an open switch and blocks the flow of the zero-collector current. When your transistor works as an SPST (single-pole single-throw) solid-state switch, you can apply a zero signal to its base to set it to OFF mode. In contrast, you must have a positive emitter potential to the base if it’s a PNP transistor. Thus, a transistor working in On Mode or saturation region will have its two junctions operating in forwarding bias mode. The max collector current flow = I C= V CC/R L).Here, the transistor works as a closed switch.Base-emitter junction stays in forwarding bias mode.Base-collector junction stays in forwarding bias mode.The base-emitter voltage is more significant than 0.7v.You can connect the input and base to the V CC.The results that lead to this effect include applied maximum base current= maximum collector current= minimum collector-emitter voltage drop. Thus, placing the transistor switch in a fully on state. When your transistor operates in the saturation region, it stays in forwarding bias mode, allowing a series of results to generate a small depletion layer.Īlso, it will enable the maximum current to flow through the transistor.

In truth, a transistor switch operating in the cutoff region or OFF mode has two junctions working in reverse bias modes.Īdditionally, if you’re using a PNP transistor, the emitter potential will harm the base. There is no collector current flow (I C = 0).Here, the transistors work as an open switch.Base-emitter junction also stays in reverse bias mode.Also, the base and input remain grounded (0v).The base-collector junction stays in reverse bias mode.The base-emitter voltage is less than 0.7v.These operating conditions cause no current to flow through the device.Īlso, there’s a large depletion layer over the circuit, which causes the transistor to switch entirely off. Cutoff Regionįor transistor switches operating in the cutoff region, the operating conditions are zero output collector current (I C), zero input base current (I g), and maximum collect voltage (V CE).

Transistor switches have two operating regions, including the cutoff and the saturated region. Transistors don’t need human intervention and can turn on and off based on the current supply. While the other switches are mainly mechanical, transistor switches are purely electrical. Since all buttons have the same functions, why do we prefer a transistor? We have different types of switches, including pushbutton switches, slide switches, toggle switches, etc.ĭespite the variety of controls, why do we use transistors as switches? So, hang in there! Why We Use Transistors as Switches In this article, you’ll learn everything about transistor switches and how they work.Įven if it’s complicated, we’ll break it down for you. Plus, you can use both NPN and PNP transistors as switches. Transistors are devices generally used for generating, controlling, and amplifying electrical signals.īut did you know transistors could be what you need for switching applications? Yes, we can have a transistor operate as a switch.Īlso, it’s easy to use a transistor as a switch in any circuit, and it works effectively for the closing and opening of your courses.

Npn transistor as a switch