Compare JFET with MOSFET.

1 Answer

Answer :

Particulars
JFET
MOSFET
1) Type
Voltage controlled device
Voltage controlled device
2) Mode of operation
Operates only in depletion mode
Operates in depletion and enhancement mode
3) Input impedance
Higher
Higher than JFET 
4) Characteristic curve
More flat
Less flat than FET
5) Gate to source junction
Only reverse bias
Forward or reverse bias
6) Gate connection
Not isolated from substrate
Isolated by SiO2 layer from substrate

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Last Answer : BJT MOSFET IGBT BJT is a current controlled device. MOSFET is a voltage controlled device. IGBT is a voltage controlled device. The input impedance of BJT is low. ... is minority carrier device. MOSFET is majority carrier device. IGBT is minority carrier device.

Description : Define junction field effect transistor (JFET) and give an example.

Last Answer : Junction Field-Effect Transistor: It is a semiconductor device having three terminals, namely Gate, Drain and Source, in which the current flow is controlled by an electric field set up by an external voltage applied ... : i) n-channel JFET and ii) p-channel JFET Examples of JFET: BFW 10, BFW 11 

Description : Describe operation of N-channel JFET

Last Answer : Operation of N-channel JFET  1) When VGS = 0 volt: When a voltage is applied between the drain and source with a DC supply voltage VDD with VGS = 0 V, the electrons flow from source ... to zero. The gate to source voltage at which current reduces to zero is called as pinch-off voltage.

Description : While biasing JFET if drain and source are interchanged, then (A) device will work normally (B) device will get damaged (C) device will work but value of drain current will affected (D) device will not operate at all

Last Answer : B

Description : State 2 advantages of JFET over BJT.

Last Answer : Advantages of JFET over BJT: 1) High input impedance 2) Better thermal stability 3) Produce less noise 4) Smaller than BJT 5) Rugged in construction and simpler to fabricate 6) High degree of isolation between Input and Output. 

Description : With the help of N-channel JFET describe the effect of input voltage VGS on output current ID.

Last Answer : Working of N channel FET: * When a voltage is applied between the drain and source with a DC supply (VDD), the electrons flows from source to drain through narrow channel ... where the channel gets completely blocked and the drain current becomes zero is called pinch- off voltage. 

Description : The voltage gain of a common -source JFET amplifier depends up on its  (1) Input impedance (2) Amplification factor (3) Dynamic drain resistance (4) Drain load resistance

Last Answer : B

Description : The transit time of the current carriers through the channel of a JFET decides it's?

Last Answer : The transit time of the current carriers through the channel of a JFET decides it's gate characteristics.

Description : Describe the operation of N channel enhancement type MOSFET with diagram.

Last Answer : As its name indicates, this MOSFET operates only in the enhancement mode and has no depletion mode. It operates with large positive gate voltage only. It does not conduct when the ... of charge carriers attracted to the positive gate. Thus drain current is controlled by the gate potential.

Description : State advantages of MOSFET.

Last Answer : Advantages of MOSFET * MOSFETs provide greater efficiency while operating at lower voltages. * Absence of gate current results in high input impedance. * High switching speed. * They operate at lower ... due to lower resistance of channel. * They are easy to manufacture. * They are portable.

Description : Describe with neat sketch the construction and working principle of MOSFET.

Last Answer : Construction and working principle of MOSFET:  A) Depletion type MOSFET: Construction: The N-channel depletion type MOSFET is formed on P-type silicon substrate with two heavily ... accumulation of electrons and hence more current. Thus the MOSFET is a gate voltage controlled device.

Description : State the applications of MOSFET

Last Answer : Applications of MOSFET: i) Switching-mode-power-supplies (SMPS) and linear power supplies. ii) Brushless DC motor drives iii) Solid state DC relay iv) Automobile applications v) Stepper motor controller vi) Lighting controls vii) Solenoid drivers viii) Robotics ix) Induction heating

Description : A certain power MOSFET has a maximum junction temperature specification of 1500o C, a junction-to-case thermal resistance of 1.00 C/W, and a junction-to ambient thermal resistance of 600 C/W. If the ambient temperature is 300o C ... the device will be A) 1.52 W B) 1.72 W C) 1.92W D) 2.00 W

Last Answer : A certain power MOSFET has a maximum junction temperature specification of 1500o C, a junction-to-case thermal resistance of 1.00 C/W, and a junction-to ambient thermal resistance of  ... 300o C, then the maximum allowable power dissipation in the device will be 2.00 W 

Description : When does the Body bias effect occur in an n-channel MOSFET?  A) When the Source voltage is less the Bulk voltage B) When the Source voltage is equal to or greater the Bulk voltage C) When the Drain voltage is equal to the Bulk voltage D) When the Gate voltage is equal to the Bulk Voltage 

Last Answer : When does the Body bias effect occur in an n-channel MOSFET?  A) When the Source voltage is less the Bulk voltage B) When the Source voltage is equal to or greater the Bulk voltage C) ... voltage is equal to the Bulk voltage D) When the Gate voltage is equal to the Bulk Voltage 

Description : The threshold voltage of an n- channel enhancement mode MOSFET is 0.5V when the device is biased at a gate voltage of 3V. Pinch off would be occurs at a drain voltage of (A) 1.5V (B) 2.5V (C) 3.5V (D) 4.5V

Last Answer : The threshold voltage of an n- channel enhancement mode MOSFET is 0.5V when the device is biased at a gate voltage of 3V. Pinch off would be occurs at a drain voltage of 2.5V

Description : Which phenomenon is present in thyristors but absent in BJT, MOSFET and IGBT ? (A) forward conduction (B) latching (C) forward blocking (D) reverse breakdown

Last Answer : Which phenomenon is present in thyristors but absent in BJT, MOSFET and IGBT ? (A) forward conduction (B) latching (C) forward blocking (D) reverse breakdown

Description : A MOSFET has how many terminals?

Last Answer : A MOSFET having three terminals 1st one is Gate (insulated), 2nd one is Source and 3rd one is Drain.

Description : What is channel length modulation in MOSFET?

Last Answer : Shortening of lenght of the inverted channel region with increase in drain bias for large drain biases due to which current increases with drain bias and output resistance decreases is called channel length modulation in MOSFET.

Description : Why Mosfet is called Mosfet?

Last Answer : Why Mosfet is called Mosfet?

Description : In MOSFET, the polarity of the inversion layers is the same as that of?

Last Answer : In MOSFET, the polarity of the inversion layers is the same as that of majority carriers in the source.

Description : MOSFET uses the electric field of?

Last Answer : MOSFET uses the electric field of gate capacitance.

Description : Is the input impedance of MOSFET more than BJT and FET?

Last Answer : Yes, the input impedance of MOSFET more than BJT and FET.

Description : Explain MOSFET gate drive circuit and totem pole configuration.

Last Answer : MOSFET gate drive circuit: The turning on and turning off of MOSFET can be controlled from gate to source voltage signal. If the gate to source voltage of MOSFET exceeds threshold ... this configuration, the two switches (transistors) are used in totem pole arrangement with a comparator.

Description : Explain the formation of parasitic BJT and parasitic diode in Power MOSFET. Can parasitic diode be used in same power electronics applications?

Last Answer : Parasitic Diode: The parasitic diode is in between drain and source. The MOSFET structure itself contains parasitic diode or body drain diode. This parasitic diode allows the reverse flow of current when the ... of MOSFET as a BJT collector. Parasitic BJT operates in the cut-off region.

Description : Operating frequency of power MOSFET is higher than that of power BJT. Justify the statement.

Last Answer : Power MOSFET have high turning on and turning off capability high switching speed of MOSFET is due to the high rate of change of drain voltage. The switching losses of power MOSFET ... lower frequency. Hence, operating frequency of power MOSFET is higher than that of power BJT.

Description : Justify the statement. Antiparallel diode is connected across MOSFET.

Last Answer : In MOSFET current is flow from drain to source but when the load is inductive the current may flow in opposite direction. To avoid the opposite flow of current and to protect MOSFET the antiparallel diode is connected across MOSFET.

Description : parallel operation of MOSFET can be done more easily as compared to thyristor. why?

Last Answer : Parallel operation of MOSFET can be done more easily as compared to thyristor because the resistance of MOSFET is increases with increase in temperature. MOSFET have the positive temperature coefficient. In ... the parallel operation of MOSFET can be done more easily as compared to the thyristor.

Description : Justify. Power MOSFET is operated at high enough gate source voltage to minimize the conduction losses. 

Last Answer : MOSFET is metal oxide field effect transistor. MOSFET is a voltage controlled device. MOSFET is majority carrier device. MOSFET are of two one is n-channel MOSFET and p-channel MOSFET. Gate, ... . Hence, power MOSFET is operated at high enough gate-source voltage to minimize the conduction losses.

Description : Explain difference between enhancement MOSFET and depletion type MOSFET.

Last Answer : In enhancement MOSFET channel is not initially exists but in depletion MOSFET channel is already exists. In case of depletion MOSFET if the voltage is applied between drain and source the drain current will flow ... a channel. depletion MOSFET & enhancement MOSFET

Last Answer : Yes IGBT is costlier than BJT and MOSFET.

Last Answer : No MOSFET do not have a second breakdown problem.

Last Answer : MOSFET  are voltage controlled devices.

Last Answer : MOSFETs are of two types namely  1) enhancement type MOSFET  or  E-MOSFET 2) depletion type MOSFET  or  D-MOSFET

Last Answer : MOSFET have high current losses due to High on state resistance. Hence MOSFET is used for low power applications.

Last Answer : Because of positive temperature coefficient of mosfet the paralleling of mosfet is easier.

Last Answer : Yes MOSFET can operate at very high frequency.

Description : Explain the series and parallel operation of MOSFET. Which is suitable and why?

Last Answer : Series operation of MOSFET: To increase voltage handling capability MOSFETs are connected in series. When the MOSFETs are connected in series each MOSFET should turn on and turn off ... on and turn off time and transconductance. Each MOSFET should share current equally.  

Last Answer : Because it has a higher switching frequency and heat tolerance.

Description : What is depletion type MOSFET?..........

Last Answer : Depletion MOSFET: Depletion MOSFET is a MOSFET in which the channel already exists. If we apply a voltage between drain and source then the drain current will flow even if the gate to source ... in figure. The drain current will be reduced as the gate to source voltage made more negative.

Description : What is enhancement MOSFET?...............

Last Answer : Enhancement MOSFET: There are two types of MOSFET one is enhancement MOSFET and second is depletion MOSFET. In enhancement MOSFET channel is created by applying threshold voltage between gate and source ... mode. The enhancement MOSFET will not conduct if the gate to source voltage is zero.

Last Answer : ON state losses of IGBT is less as compared to MOSFET and BJT.

Last Answer : No, MOSFET is not the curent controlled device. The current between drain and source which is drain current is controlled by applying a voltage between gate and source hence MOSFET is a voltage controlled device. 

Last Answer : already answered here is mosfet current controlled device?

Last Answer : MOSFET provides better efficiency at high frequency and its high speed switching losses are less hence MOSFET is used for high frequency.

Description : what are the uses of MOSFET ?

Last Answer : Choppers and inverters and where high switching frequency is required.

Description : what is MOSFET ?

Last Answer : MOSFET is a type of Field Effect Transistor (FET). It is a voltage controlled transistor. MOSFET have very high input impedance. It can be use with very low current circuits. It is very fast ... of Nano ampere. There are two types of MOSFET one is enhancement mode and second is depletion mode.

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