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What is FET?
FET is abbreviation of Field Effect Transistor. This is a transistor in which current is controlled by voltage only and no current is drawn. It is a high input impedence device and is used in computers, telecommunication and control circuits. This transistor is better in certain parameters as compared to BJT, that is Bipolar Junction Transistor.
Why is it thatFET is called a voltage operated device?
since in an FET the value of the current depends upon the value of the voltage applied at the gate and drain...so it is known as voltage controlled device.. for example..in a mosfet..the current from drain to source depends upon the width of the depletion layer..which in turn depends upon the voltage applied on the gate.. so that is the reason
As the drain voltage is increased for a junction FET in the pinch off region then the drain current?
Remains constant
What is input impedance of fet amplifier?
Zin=Vds/Id [Vds=drain to source voltage ; Id = drain current]
What is bjt and jfet?
BJT is Bipolar junction transistor FET is Field effect Transistor It is a current controlled device It is voltage controlled device
A junction FET can be used as a voltage variable resistor at which stage?
nnm,n,n,mn
How fet is used as vvr?
FET AS A VOLTAGE -VARIABLE RESISTOR (VVR):FET is operated in the constant current portion of its output characteristics for the linear applications .In the region before pinch off , where Vds is small the drain to source resistance rd can be controlled by the bias voltage Vgs.The FET is useful as a voltage variable resistor (VVR) or Voltage Dependent resistor.In JFET the drain source conductance gd = Id/Vds for small values of Vds which may be expressed as gd = gdo [ 1-( VgsVp)1/2 ] where gdo is the value of drain conductance when the bias voltage Vgs is zero.The variation of the rd with vgs can be closely approximated by rd = ro / 1- KVgs ro - drain resistance at zero gate bias and K constant dependent upon FET type.Small signal FET drain resistance rd varies with applied gate voltage Vgs and FET act like a VARIABLE PASSIVE RESISTOR.Advantagesof JFETVery high input impedance order of 100 ohmOperation of JFET depends on the bulk material current carriers that do not cross junctionsNegative temperature coefficientsVery high power gainSmaller size longer life and high efficiencyAc drain resistance rd it is the ratio of change in drain - source voltage to the change in drain current at constant gate source voltageTransconductance it is the ratio of change in drain current to the change in gate source voltageat constant drain source voltageAmplification factor it is the ratio of change in drain source voltage to the change in gate source voltage at constant drain current.
Fet in cut off voltage?
fet is a voltage controlled device...cut off voltage in fet refers to that voltage of the gate - source junction at which the current flow through channel is zero
What is Cut-off voltage in fet?
fet is a voltage controlled device...cut off voltage in fet refers to that voltage of the gate - source junction at which the current flow through channel is zero
What are voltage controlled devices?
FET
Why the voltage gain of an FET amplifier is generally less than that obtained using BJT amplifier?
A FET (Field Effect Transistor) is mainly used when the input signal needs to be isolated from the output. A FET has a very high input resistance, so very little current is required from the input. Voltage gain is not the main objective when using a FET.
How FET works as an voltage variable resister?
A: Imagine a silicon bar where a field is impressed from both sides as the field or voltage increases the bar of silicon will restrict migration of electrons like chocking a wind pipe. There could be better explanations around but basically this is it.
What is FET?
FET is abbreviation of Field Effect Transistor. This is a transistor in which current is controlled by voltage only and no current is drawn. It is a high input impedence device and is used in computers, telecommunication and control circuits. This transistor is better in certain parameters as compared to BJT, that is Bipolar Junction Transistor.
What is JFET and VVR?
JFET as a VVR-Voltage Variable ResistorFET is a device that is usually operated in the constant-current portion of its output characteristics. But if it is operated on the region prior to pinch-off (that iswhere VDS is small, say below 100 mV[ohmic region of JFET]), it will behave as a voltage-variable resistor (WE). It is due to the fact that in this region drain-to-source resistance RDS can be controlled by varying the bias voltage VGS. In such applications the FET is also referred to as a voltage-variable resistor or volatage dependent resistor. It finds applications in many areas where this property is useful.Figure shows the drain characteristic curves for a 2N 5951 in the ohmic region (i.e. for low VDS). From the characteristic curve it can be seen that RDS varies with VGS. For example, when VGS = 0, RDS = 133 ohm and when VGS = - 2 V, RDS = 250 ohm. Because of this a JFET operating in the ohmic region with small ac signals acts as a voltage-controlled resistance.Note that the drain curves shown in figure,extend on both sides of the origin. This means that a JFET can be employed as a voltage-variable resistorfor small ac signals, typically those less than 100 mV. When it is employed in this way, it does not require a dc drain voltage from the supply. All that is required is an ac input signal.
Why you use FET?
FET's improve the switching frequency from KHZ to MHZ.. FET can be used as temperature sensor.. and mosfet is used as a switch..
How biasing of FET differs from biasing of BJT?
in BJT forwardbiasing & reverse biasing are carried out but in FET voltage divider biasing &self biasing are carried out.
Why is it thatFET is called a voltage operated device?
since in an FET the value of the current depends upon the value of the voltage applied at the gate and drain...so it is known as voltage controlled device.. for example..in a mosfet..the current from drain to source depends upon the width of the depletion layer..which in turn depends upon the voltage applied on the gate.. so that is the reason
