The MOSFET - The MOSFET p channel n channel Physics of the...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
The MOSFET p channel Physics of the device B v (body or substrate) is the lowest voltage in the circuit (we will also assume that B v = S v ). With GS v =0 and D v > B v , S v > B v , the transistor internally has two reverse-biased junctions from the n-type drain to the p-type bulk and from the n-type source to the n-type bulk. Therefore, no current can flow in this device. For this scenario, the device is said to be in cutoff and D i = S i = G i = B i =0. As we increase GS v above 0, holes in the p-type semiconductor are repelled away from the oxide and a new depletion layer forms under the oxide. When GS v > T V a layer of electrons is formed in the semiconductor immediately under the oxide. This layer is called an inversion layer (channel). The charge in the layer is proportional to the voltage difference between the gate and the channel. At the source side, the gate-to-channel voltage is GS v . At the drain end, the gate-to-channel voltage is GD v . As long as DS v is small enough, both GS v and GD v will be greater than T V and we will have a continuous channel from the source to the drain end. The average gate-to-channel voltage is 2 2 2 DS GS DS GS GS GD GS v v v v v v v - = - + = + . So the average charge is proportional to
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 3

The MOSFET - The MOSFET p channel n channel Physics of the...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online