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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
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Ezra1. 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.
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Advantages of fet over bjt?
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
What are the three element of a transistor?
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.
Why there is no thermal runaway in fet?
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.
Switching speed is high for mosfet or bjt?
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
Why FET is called as a unipolar transistor?
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.
