Lecture 16

Ee105 fall 2013 lecture 16 slide 9 prof ming c wu eect

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Unformatted text preview: cteris?cs §༊  The MOS characteris?cs are measured by varying VG while keeping VD constant, and varying VD while keeping VG constant. §༊  (d) shows the voltage dependence of channel resistance. EE105, Fall 2013 Lecture 16 – Slide 8 Prof. Ming C. Wu 4 L (Gate Length) and tox (Gate Oxide Thickness) Dependence §༊  Small gate length and oxide thickness yield low channel resistance, which will increase the drain current. EE105, Fall 2013 Lecture 16 – Slide 9 Prof. Ming C. Wu Effect of Gate Width: W §༊  As the gate width increases, the current increases due to a decrease in resistance. However, gate capacitance also increases thus, limi?ng the speed of the circuit. §༊  An increase in W can be seen as two devices in parallel. EE105, Fall 2013 Lecture 16 – Slide 10 Prof. Ming C. Wu 5 Channel Poten?al Varia?on §༊  Since there’s a channel resistance between drain and source, and if drain is biased higher than the source, channel poten?al increases from source to drain, and the poten?al between gate and channel will decrease from source to drain. EE105, Fall 2013 Lecture 16 – Slide 11 Prof. Ming C. Wu Channel Pinch- Off §༊  As the poten?al difference between drain and gate becomes more posi?ve, the inversion layer beneath the interface starts to pinch off around drain. §༊  When VD – VG = Vth, the channel at drain totally pinches off, and when VD – VG > Vth, the channel length starts to decrease. EE105, Fall 2013 Lecture 16 – Slide 12 Prof. Ming C. Wu 6 Channel Charge Density Q = WCox (VGS − VTH ) §༊  The channel charge density is equal to the gate capacitance...
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This note was uploaded on 01/22/2014 for the course EE 105 taught by Professor King-liu during the Fall '07 term at Berkeley.

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