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MOSFETs have three leads, a source, a gate, and a drain. Bipolartransistors also have three leads, but they are called emitter, base,and collector. These leads roughly correspond to one another, ie, theemitter is like the source, the base is like the gate, and the collectoris like the drain. Making the base (gate) more positive (for NPN andN-MOSFETs) or negative (for PNP or P-MOSFETs) with respect to theemitter (source) causes more current to flow from collector (drain) toemitter (source).This terminology is totally confusing, and, sadly, you just have to getused to it if you want to talk about these things.MOSFETs are used to construct CMOS devices, and are thus the maintransistor component to microprocessors. They are also good forconstructing huge power transistors, which are easier to control due tothe lack of required gate current.Bipolar transistors are generally more useful for analog design, wherethe lower noise, more easily predicted voltage requirements, and lowercontrol voltages are useful.For a FET, the electrostatic field of charges on the control terminal(the gate) is used to moderate the output. MOSFETs have a silicon oxidelayer that insulates the gate from the charge. JFETs use areverse-biased PN junction's depletion region to isolate the gate fromthe source and drain. For bipolar transistors, the movement of chargesacross PN junctions controls the output.
1. MOSFET is used for creating
while BJT is used only for Amplifiers
2. Large current causes large losses by H = i*i*R*time.which can destroy small devices(ICs).
A large current source is very difficult to implement in small DC devices
MOSFET is voltage controlled.( control gate voltage to control the current through MOSFET)
hence less heat
BJT is current controlled ( control the gate current to control the current through BJT) .
hence more current , more heat
which one would you choose?
MOSFET is voltage operating devices and Bipolar is a current operating devices
mosfet is bassicaly a FET device means Field Effect Transistor. the field is controlled by applied voltage to the gate....so MOSFET metal oxide semiconductor field effect transistor is voltage controll device. while the BJT bipolar junction transistor is controll by gate current means current value at base. so it is current controll device.
