Electronics - Bipolar Junction Transistors (BJT) - Discussion

The whole digital world considers only two states. That is on and off/ 1 and 0. So now the transistors saturation and cut-offs can be considered as on and off respectively.

Is transistor operates in saturation or active region itself (as the amplify or switching) or we do this?

When transistor is used as an amplifier then it has to be operated in active region and when the transistor is use in a digital circuits then it can be operated in Cut off (open s/w means 0) or in saturation region (closed s/w means 1).

In digital electronics world transistor is nothing but a switch, switch has two modes can be ON or OFF. To get the desired output you decide what you need it ON or OFF. Now we conventionally assume if ON is 1 then OFF is 0.

So saturation mode means your circuit is closed which also means your switch is ON which lead us to say our output is 1 and cutoff region is opposite. Common sense if you transistor in saturation mode output is max which is 1 however in cutoff it is opposite.

Key points : Saturation MEANS ON what is ON your switch also means circuit is closed. And cut OFF is OFF what is OFF your switch means circuit is open means 0 output.

As we know that when we talk about digital circuit then one thing is very clearly understand the operation of the circuit is totally depend on logic 1 (i.e high voltage) or 0 (i.e. Low voltage) and we can say that saturation is logic 1 and cut off region is logic 0.

So no doubt when transistor are used in digital circuit they operate in saturation and cut off region only. Because it full fill the digital circuit requirement.

Digital circuit means 0 or 1 therefore cutoff means 0 and saturation means 1, that's all.

Saturation and cut off region.

What about active, breakdown and linear region?

In which region, Analog circuit will work?

In which region, Analog circuit will work?