Transistor .. i suppose you are referring to Bipolar Junction Transistor .. Here you know that the
collector current is proportional to the base current
as
Ic = ( Beta ) Ib hence .. here Ib is the input current
ane Ic is the output current .. so we called it a current
controlled device.
Transistor .. i suppose you are referring to Bipolar Junction Transistor .. Here you know that the
collector current is proportional to the base current
as
Ic = ( Beta ) Ib hence .. here Ib is the input current
ane Ic is the output current .. so we called it a current
controlled device.
besides, if u see in active region the collector current is independent of collector voltage and only depends upon the base current. so we could say the device out put depends upon the input current ie base current
hi because in transistor there are primarily 3 currents ,ie,Ib,Ic and ie=ib+ic for further refernce u can see the working and explanation of" TRANSISTOR CURRENT FLOW MECHANISM" IN ANY OF THE STANDARD book in electronics
A bipolar transistor is said to be current controlled because when it is biased in the active region the output (collector) current is controlled from the input (base) current.
A bipolar trasistor is said to be in the active region when BE junction is forward biased while CB junction is reverse biased (or viceversa)
In this situation the collector current depends mainly on base current via β (Ic=β*Ib) and only marginally (second order effect) from collector Voltage (Early effect). Also β depends on Ic.
Because voltage at input Vbe(base to emmiter voltage) remains at about 0.6V and variation of current into the base contros output variations(current, voltage both).
The Transistor was described as " Trans-fer of current across a re-Sistor" by its inventor.
No matter what you do , The base bias voltage may remain same or vary slightly but the base current can be varied widely, resultingin a corresponding increase in Collector current.
(The Base-Emitter junction(diode) has a fixed Forward V of ~0.6 to 0.65vdc. like any other pn junction)
I think it's too clear from previous posts. An input current, the base current in the common emmitter stage is the parameter that makes the output variable, the collector current goes up or low. So the collector current follows the variations the input (base) current dictates.