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

1 Answer

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 to gate terminal. 

Types of JFET are: i) n-channel JFET and ii) p-channel JFET Examples of JFET: BFW 10, BFW 11 

Related questions

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 : Define Depletion region and Barrier voltage of PN junction.

Last Answer : 1. Depletion region : The region consisting of immobile positive charge at n-side and immobile negative charge at p-side near the junction acts like a barrier and prevents the further flow of ... charge formed at the p-n junction is called barrier voltage, barrier potential or junction barrier.

Description : Define biasing of transistor

Last Answer : Biasing of transistor is the process that makes the base emitter junction of transistor always forward biased and collector junction reverse biased for achieving the faithful amplification .

Description : Define armature reaction in an alternator. Explain the effect of armature reaction at various P.F. of loads of alternator.

Last Answer : Armature Reaction: The effect of armature flux on main flux is called as armature reaction.  Armature Reaction at Various Power Factors: When armature is loaded, the armature flux modifies ... lagging p.f. For capacitive loads the effect of flux is partly distorting and partly strengthening.

Description : Compare JFET with MOSFET.

Last 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 ... 6) Gate connection Not isolated from substrate Isolated by SiO2 layer from substrate

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 : 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 :  applications of P-N junction diode

Last Answer : 1.It is used as rectifier in DC power supply 2.It is used as free wheel diode across relay or inductive load 3.It is used as switch in logic circuits used in computers 4.It is used as detector in demodulation circuits of communication receiver 

Description : Define α & β and derive the relation between (α) &) (β) of transistor.

Last Answer : α : The ratio of output collector current IC to input emitter current IE in the CB configuration is called current gain alpha (α).  β : The ratio of output collector current IC to the input base current IB in the CE configuration is ... ( 1/β) + 1  hence 1/ α = (1+β )/ β  Therefore, α = β /(1+β)

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 : The leakage current of PN junction is caused by?

Last Answer : The leakage current of PN junction is caused by heat energy.

Description : Define α and β of the transistor. 

Last Answer : α: The ratio of collector current IC to emitter current IE for a constant collector to base voltage VCB in the CB configuration is called current gain alpha (α).   β : The ratio of collector ... a constant collector to emitter voltage VCE in the CE configuration is called current gain beta (β) .

Description : Compare P.N.P and N.P.N transistor.

Last Answer : Parameter PNP transistor NPN transistor Definition Two blocks of p- types semiconductors are separated by one thin block of n-type semiconductor. Transistor in which two ntype layer ... Positive Voltage  Emitter Terminal Collector Terminal Ground Signal High Low

Description : Transistor operating configurations

Last Answer : Transistor operating configurations

Description : Explain working of n-p-n transistor in unbiased condition.

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Description : With neat diagram explain working of NPN transistor.

Last Answer : N-p-n transistor is made by sandwiching thin layer of p-type semiconductor between two layers of n-type semiconductor. It has three terminals - Emitter, Base and collector. The npn transistor has two ... up in the collector as it is more positive. In this way, current flows in the transistor.

Description : Draw and explain self-basing of a transistor.

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Description : Compare between CB , CE & CC transistor configuration.

Last Answer : Parameter CB CE CC I/P impedance Low Or 50Ω Medium Or 600Ωto 4kΩ High Or 1 MΩ Current Gain Less than or equal to 1 High Highest Voltage Gain Medium Medium Less ... k Ω to 50 k Ω Low Or 50 Ω Phase shift between input and output 0° 360° 0° 

Description : Why transistor is called as bipolar device.

Last Answer : BJT is called bipolar device because in BJT current conduction takes place due to majority as well as minority charge carriers that is because of electrons as well as holes.

Description : Draw construction of SCR using two transistor model. Explain its operation.

Last Answer : Two Transistor Model of SCR or Thyristor

Description : Draw the V-I characteristics of power transistor. 

Last Answer : V-I characteristics of power transistor:

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Last Answer : Concept of thermal runaway:  1.We know that  IC = β IB + (1+ β) ICO  Where ICO is the leakage current and ICO is strongly dependent on temperature. 2. Leakage current approximately doubles for ...   Thermal runaway can be avoided by : 1) Using stabilization circuitry 2) Heat sink 

Description : List various transistor biasing methods.

Last Answer : Types of biasing methods: i. Base bias (or fixed bias) ii. Base bias with emitter feedback. iii. Base bias with collector feedback iv. Voltage divider bias (or self bias) v. Emitter bias. 

Description : What is the main use of a transistor?

Last Answer : Main use of a transistor as amplifier and as switch.

Description : Define magnetic field strength and state its unit.

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Last Answer : To avoid the effect of stray magnetic field in A.C. bridges we can use magnetic screening.

Description : Under Following conditions Ferranti effect occurs: 

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Description : Explain in brief ‘Hall effect sensor’. 

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Description : what is Ferranti effect?

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Description :  Field intensity formula

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Description : Which of the following laws relates the magnetic field to the magnitude, direction, length, and proximity of the electric current? A) Lenz’s law B) Faraday’s law C) Biot–Savart law D) None of these

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Description : What is the direction of the induced electric field?

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