BJT saturation region

We will be talking about bipolar junction transistor (BJT) saturation region (FULLY ON) in this post. Also, Links for the other two operation regions are provided immediately.


A transistor is said to be saturated (Fully ON) when it is biased in such a way that current passes from the Emitter (E)  to the Collector (C). In NPN and PNP bipolar junction transistors (BJTs), connecting the base (B) to the collector (C) makes the PN-junction from the base (B) to the emitter (E) to be forward bias. As a result of this, the base (B) to the collector (C) of the transistor shorts thereby causing high current to flow from the emitter (E) to the collector (C). In this state the transistor is said to be saturated or fully ON. 

The below circuits explain and illustrate the operations of the saturation regions for both NPN bipolar junction transistor (BJT) and PNP bipolar junction transistor (BJT). The resistor R in the circuits limits the current that will pass through the Light Emitting Diode (LED)


You might also want to read the other two bipolar junction transistor (BJT) operation regions below apart from the saturation region (fully off).


In active region the transistor is bias so that the base (B) measures a higher potential difference (Pd) to the emitter (E) but lower than the collector (C) to the emitter (E). In this region the transistor is always active. This is the biasing mode or region which transistor amplifiers…Read more> BJT Active Region


In cut off or fully off region, the transistor is bias in such a way that both junctions are reverse so that no current will pass from the emitter (E) to the collector (C). In this mode, the transistor is in OFF mode…..Read more here > BJT Cutoff Region


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