A: Initially the construction of an FET closely resemble the double diffused bipolar epitaxial transistor Both begins with an n+ substrate n- forming a 4 layer structure. another distinguishing feature is the electrical bonding of the upper most n+ diffusion [source] however with this bonding a parasitic diode in parallel cathode drain to source fortunatelly by virtue the polarity operation is unaffected. All in all FET have higher power, higher voltage rating practically no thermal runaway and a greatly inhibited secondary breakdown characteristics
1. BJT is a Bipolar Junction Transistor, while MOSFET is a Metal Oxide Semiconductor Field-Effect Transistor.
2. A BJT has an emitter, collector and base, while a MOSFET has a gate, source and drain.
3. BJTs are preferred for low current applications, while MOSFETs are for high power functions.
4. In digital and analog circuits, MOSFETs are considered to be more commonly used than BJTs these days.
5. The operation of MOSFET depends on the voltage at the oxide-insulated gate electrode, while the operation of BJT is dependent on the current at the base.
mainly i will tell ttwo advantages:- 1)in FET "thermal runaway" never occurs but in bjt it occurs easily...thermal runaway means overheating and damage of fet due to different biasing voltages.. 2) since FET is a unipolar device so only one carrier type is required here ,but bjt is a bipolar device .. 3) FET is smaller in size than BJT of same rating. i mean to say that at the place of 10 bjts we can use 90 FETs ..so area cosumption is less
For a BJT transistor the three basic elements are collector, base and emitter. For a FET transistor are drain, gate and source which are analogous for the BJT parts mentioned before.
in FET the conduction is due to the majority carriers. here the minority carrier conduction doesn't takes place as in BJT. hence the current flow depends only on the majority carriers . hence ther is no thermal runaway in FET.
generally bjt is faster than fets...because of many intrinsic junction capacitances between ...source and drain and bulk and gate,,,.. but now a days due to advancement in scaling fet is reduced in size sooo much that it became faster than bjt... mosfet is faster because of scaling. small channel length. even though it is slower but distance to be travelled is less
The FET is a semiconductor device with the output current controlled by an electric field. Since the current is carried predominantly by one type of carriers, the FET is known as a unipolar transistor.
Disadvantage:Easy to damage when compared to BJT
because the fet is made out of carbon metal oxide and the bjt is made out of silicon or germanium
in BJT forwardbiasing & reverse biasing are carried out but in FET voltage divider biasing &self biasing are carried out.
BJT is Bipolar junction transistor FET is Field effect Transistor It is a current controlled device It is voltage controlled device
JFET (Junction Field-Effect Transistor) is a voltage-controlled device where current flow is controlled by an electric field across a semiconductor junction. BJT (Bipolar Junction Transistor) is a current-controlled device where current flow is controlled by the amount of current entering the base terminal. JFETs are majority carrier devices, while BJTs are minority carrier devices.
land pe char hai
mainly i will tell ttwo advantages:- 1)in FET "thermal runaway" never occurs but in bjt it occurs easily...thermal runaway means overheating and damage of fet due to different biasing voltages.. 2) since FET is a unipolar device so only one carrier type is required here ,but bjt is a bipolar device .. 3) FET is smaller in size than BJT of same rating. i mean to say that at the place of 10 bjts we can use 90 FETs ..so area cosumption is less
bjt is bipolar device whr fet is unipolar....fet is input resistance thts y fet gain is less compared to bjt..... The applications that will prefer bipolar junction transistors to field effect transistors are applications that require fast switching.
BJT & FET parameters are temperature dependent. In BJT the collector junction resistance decreasing ( collector current increasing) with temperature raise.Due to the highe temperature & current transistor will damage quickly. In FET drain resistance increasing (drain current decreasing ) with increasing temperature.Due to this property it will not damage easily. We can say from the above two statements FET is more temperature stable.FET can use in highe temperature applications.
common emitter using fixed bias
For a BJT transistor the three basic elements are collector, base and emitter. For a FET transistor are drain, gate and source which are analogous for the BJT parts mentioned before.
For a BJT transistor the three basic elements are collector, base and emitter. For a FET transistor are drain, gate and source which are analogous for the BJT parts mentioned before.