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Compare n-channel and p-channel JFET with respect to their device features and voltage-current characteristics.

Mumbai University > Computer Engineering > Sem 3 > Electronic Circuits and Communication Fundamentals

Marks: 5 Marks

Year: May 2016

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N-channel JFET

1. Device Features

  • A small bar of extrinsic semiconductor material, n type is taken and at its two end, two ohmic contacts are made which are the drain and source terminals of FET
  • Heavily doped electrodes of p type materials form p-n type junctions on each side of the bar.
  • The thin region between the two p gates is called the channel.
  • Since this channel is in the n-type bar, the FET is known as n-channel JFET.
  • The electrons enter the channel through the terminal called source and leave through the terminal called drain.
  • The terminals taken out from heavily doped electrodes of p type material are called gates.
  • Usually, these electrodes are connected together and only one terminal is taken out, which is called gate.

2. Voltage-Current Characteristics

  • The figure shows the V-I characteristics of a n-channel JFET.
  • The curve represents relationship between the drain current I_D and drain to source voltage $V_{DS}$ for different values of $V_{GS}$.

enter image description here

P-channel JFET

1. Device Features

  • The device could be made of p type bar with n type gates.
  • The device characteristics of n type and p type JFET is similar, the only difference being that in n channel JFET the current is carried by electrons while in p-channel JFET, it is carried by holes.

2. Voltage-Current Characteristics

  • In a p-channel JFET the source is positive with respect to the drain.
  • Here the source is the source of holes which flow through the channel to the drain.
  • The pinch-off is achieved by making the source to gate voltage, source to gate voltage negative there by reverse biasing the p-n junction diode formed by the channel and the gate.
  • The figure shows the V_I characteristics of p channel JFET.

enter image description here

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