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When a BJT is working as an electrical switch?
If the transistor is biased into the linear region, it will operate as an amplifier or other linear circuit, if biased alternately in the saturation and cut-off regions, then it is being used as a switch, allowing current to flow or not to flow in other parts of the circuit.
How does a BJT switch work?
Bipolar junction transistor (BJT) has three terminals and two junctions. The function of the transistor is to amplify the signal. The transistor acts as a switch in the cut-off mode and the saturation mode. The transistor is fully off in the cutoff region and fully on the saturation region.
How does a BJT switch work in a switching circuit?
In a switching circuit, the goal is not to provide proportional changes in output current; rather, we simply want to drive the transistor into full conduction. Thus, a BJT switch transitions between cutoff mode and saturation mode. We don’t limit the input voltage or the input current in an attempt to keep the transistor in forward active mode.
How is a BJT used as an example?
Using a BJT as a Switch: An Example. Remember that the controlled current through a transistor must go between collector and emitter. Since it is the current through the lamp that we want to control, we must position the collector and emitter of our transistor where the two contacts of the switch were.
How does a bipolar junction transistor work as a switch?
This video tutorial demonstrates how a bipolar junction transistor can allow a low-voltage signal to control a high-power load. Transistors are active devices that can perform both switching and amplification.
What is the minimum base current for a BJT?
I C (sat) is the current that the load R C requires. V CE (sat) is specified in the datasheet of the BJT that you are going to use. After calculating I C (sat), the next thing to figure out is the minimum base current, I B (min), needed to make sure to produce I C (sat).