What is P Channel JFET? its working, construction, and Application

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Channel JFET is a JFET whose channel is composed primarily of holes as the charge carrier. In the case of p-channel JFET, the major portion of the device is made of p-type into which embedded are the two small n-type regions. Thus it has an n-type gate terminal and p-type source and drains, causing the channel to be of p-type where the holes will be the majority charge carriers. Read the full article to get complete info on P Channel JFET its working construction and its Application.

Working of P-Channel JFET

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Case I: If VDS = 0 and VGS = 0, the device will be idle with no current i.e. IDS = 0.
Case II: Now consider VDS to be –ve while VGS is 0. At this state, the current flows from the source to the drain (as per conventional direction) as the holes within the p-substrate move towards the drain while being repelled from the source. The value of this current is restricted only by the channel resistance and is seen to increase with a decrease in VDS (Ohmic region). However once the pinch-off occurs (VDS = VP), the current IDS saturates at a particular level IDSS, during which the device acts like a constant current source

Case III: Next, let VGS = +ve while VDS is -ve. Here the effect exhibited is similar to that in Case II with the fact that the saturation occurs at a faster rate as the VGS becomes more and more positive. Similar to that seen in n-channel JFETs, even here the current ceases to flow as the value of VDS becomes equal to VP, turning the device into an OFF state.

Construction of P-Channel JFET

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The construction is similar to the N channel JFET except that it consists of a P-type silicon bar with two N-type heavily doped regions diffused on opposite sides of its middle part. The JFET in which the current conduction takes place only due to holes as majority charge carriers is known as P channel JFET. The two PN junctions are formed by the N region and the space between that is the P region is called a channel. A single wire is taken in the form of the terminal when both the N-type regions are connected internally known as the gate (G). The following figure shows the P Channel JFET its working construction and Application.

P-Channel JFET Characteristics

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  • Ohmic Region
  • Saturation Region
  • Cutoff Region
  • Breakdown Region

Applications

  • Analog Switches
  • Choppers
  • Sample and Hold Circuit

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