Saturation region of a transistor

In summary, the saturation region of a bipolar transistor is when the voltage on the collector drops below the voltage on the base, causing the base/collector junction to become forward biased. This results in a drastic drop in current gain and is represented in the left hand region of the I-V plot for a bipolar transistor.
  • #1
titangsu
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I have not any clear idea about the saturation region of a transistor. Can anyone help me in detail? What parameter actually becomes saturated in this region? Why are both the junctions becomes forward biased? Is it possible to widen this region for a particular transistor?
 
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  • #2
I assume from the question that you mean a bipolar transistor. Bear in mind that "saturation" means something different for MOS and bipolar transistors. The word "region" doesn't refer to a region of the transistor, it refers to a region of the voltage-current parameter space. When the voltage on the collector drops below the voltage on the base, then the base/collector junction becomes forward biased and by definition this is the saturation region. When this happens, carriers are no longer traveling as intended from the emitter to the collector, and the current gain drops drastically.

It corresponds to the left hand region on the attached I-V plot, which I copied from Wikipedia, http://en.wikipedia.org/wiki/Bipolar_junction_transistor#Regions_of_operation
 

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1. What is the saturation region of a transistor?

The saturation region of a transistor is a state in which the transistor is fully turned on and the current through it is at its maximum value.

2. How is the transistor's saturation region different from its active region?

In the active region, the transistor is not fully turned on and the current is not at its maximum value. In the saturation region, the transistor is fully turned on and the current is at its maximum value.

3. What determines when a transistor enters the saturation region?

The transistor enters the saturation region when the voltage between the base and emitter reaches a certain threshold, called the saturation voltage, and the base current is large enough to fully turn on the transistor.

4. Can a transistor stay in the saturation region indefinitely?

No, a transistor cannot stay in the saturation region indefinitely as it needs a certain amount of voltage and current to remain in this state. If the voltage or current changes, the transistor will exit the saturation region.

5. How does the saturation region affect the behavior of a transistor in a circuit?

In the saturation region, the transistor acts as a closed switch, allowing a large amount of current to flow through it. This can be useful in certain circuit designs, such as in amplifiers or digital logic circuits.

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