Why FET is a current controlled device?
FET is a voltage-driven/controlled device, i.e. the output current is controlled by the electric field applied. The current through the two terminals is controlled by a voltage at the third terminal (gate). It has a high input impedance. So, a FET is a voltage-controlled current source.
Which transistor is a current controlled device?
A field-effect transistor (FET) controls the width of a current path called the channel that is created by the voltage applied across the gate and source terminals. Changes in the channel width causes the drain-source resistance to change. Therefore, an FET is a voltage-driven device.
Which type of device is BJT?
A bipolar junction transistor (bipolar transistor or BJT) is a type of transistor that uses both electrons and holes as charge carriers. A bipolar junction transistor, also called bipolar transistors, is a three-terminal device that can function as electronic switches or signal amplifiers.
Which device is FET?
The field-effect transistor (FET) is a type of transistor that uses an electric field to control the flow of current in a semiconductor. FETs are devices with three terminals: source, gate, and drain.
Is considered a current controlled device?
Whereas the bipolar transistor can be considered a current-controlled device (the current in the base), the field effect transistor is a voltage-controlled device. Transistor family. The terms base, collector, and emitter are now replaced by gate, source, and drain, respectively.
Which is a current controlled device BJT or FET?
FE’T is a voltage controlled device, i.e. voltage at the input terminal controls the output current, and whereas BJT is a current controlled device i.e. the input current controls the output current. As shown in the Fig. 2.6, in BJT the output current, I_C is controlled by the base current I B. Hence BJT is a current controlled device.
How is the source drain of a BJT controlled?
FETs in general, source-drain current is controlled with a very little current from the gate. BJTs require more current, because of how it works, collector-emitter current is proportional to the current from the base.
Why is BJT called current / voltage controlled voltage / current?
In a BJT, the base is connected to the emitter via an internal resistance. The resistance is in the low ohms. Therefore, there is a means for current flow. Hence, the BJT is a current-controlled device. Specifically, the current through the device (collector to emitter — assuming an NPN) is a function of the current into the base.
What makes up the collector current in a BJT?
Depending on the doping ratio between emitter and base, emitter current is a certain multiple of the base current. Since most of this emitter current ends up as collector current, the ratio of Ic to Ib is also relatively fixed for a given transistor (depending on relative doping levels of emitter and base).