Transistor as a Switch Circuit

[BenzT]

Hi,

I want to know the behavior of Transistor under saturation region..



Pls clarify me

 

[betwixt]

Aways the circuit with the lowest value resistors will be fastest. The reason is the charges in the transistor junctions can be created and removed faster when there is a lower resistance path for them to flow through. The circuit with lowest resistor values is also the least efficient at power usage so there is a trade-off between speed and efficiency.
Note that as they are, all the circuits will be extremely fast anyway. If there is a capacitive load from a following stage, (a) will be fasters than (b) which will be faster than (c) because of the RC time constant of the collector resistor and load capacitance but the difference between (d), (E) and (f) will be much smaller.

Brian.

 

[waris3666]

Hello benzt,
I can simply explain u transistor as switch(although it is a switching device).By giving small signals to transistor base junction the transistor switches nd there will be some current will flow from collector to emitter. The amount of current flow from collector to emitter is decided by the voltoge or current given to the base junction.I can explain u this by an example of buzzer with transistor arrangement. If u give more current or voltage to the base of transistor u can hear louder noice from the buzzerr,that's because the voltage at gate terminal shrinks the depletion layer and hence provide more path for the current to flow. So by using different values of resistor in base terminals resulting different amplication of current at collector emitter junction. I am not sure u could understand this nd this is the simplest way I could explain.(if u know the application of transistor ithe eg I explained above will understand,if there is any problem regarding the circuit you can reply me)

 

[betwixt]

BJT = Emitter, Base, Collector, conduction is controlled by Base Current.
FET = Source, Gate, Drain, conduction controlled by Gate voltage.

Therefore post #3 makes little sense, especially as the transistor is near to, or saturated.

Brian.