Question

The action of a JFET in its equivalent circuit can best be represented as a

Option 1:

Current Controlled Current Source.

Option 2:

Current Controlled Voltage Source

Option 3:

Voltage Controlled Voltage Source

Option 4:

Voltage Controlled Current Source.

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Answer 1

The action of JFET in its equivalent circuit can be represented as which of the following? Explanation: In JFET equivalent circuit, the output current is controlled by the gate to source voltage and hence we can say it is a Voltage controlled current source.

Answer 2

The answer to this question is option (4) Voltage controlled current source.

Explanation:

To answer this question, let us first understand what is JEFT and then look into it's action.

Junction-gate field-effect transistor (JFET):

It is one of the simplest types of field-effect transistor which is a three terminal device , Gate(G), Source(S) and Drain(D),that can be used as switches , electrically controlled resistors, or to build amplifiers.

In JEFT, the conduction of current is mainly due to the majority charge carriers i.e. Electrons in n-channel JFET and Holes in p-channel JFET.

It consists of two pn junctions at the sides which forms two depletion layers through which conduction of current starts to occur.  

The two pn junctions formed are internally connected and a common terminal called gate is taken out.

Other terminals are source and drain that are taken out from the bar.

Now coming back to the question.

Here since the gate voltage controls the drain current, that is why we say that JEFTs are Voltage controlled current devices.

Hence option (4) is correct.