Lecture22-MOS+TranSmallSigModelAmplifiers

Lecture22-MOS+TranSmallSigModelAmplifiers - ECE 3040 - Dr....

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Unformatted text preview: ECE 3040 - Dr. Ying Zhang Georgia Tech ECE 3040: Microelectronic Circuits Lecture 22 Reading: Jaeger 4.1-4.11, 13.8, Notes ECE 3040 - Dr. Ying Zhang Georgia Tech Recapture MOS Transistor Channel Length Modulation Effect DS V L L = But the fraction of the channel that is pinched off depends linearly on V DS because the voltage across the pinch-off region is (V DS -V Dsat ) so, ( ) [ ] ( ) DS Dsat DS T GS ox n Dsat D V V V V V L C Z I I + = = 1 2 2 where is known as the Channel-Length Modulation parameter and is typically: 0.001 V-1 < <0.1 V 1 Channel Length Modulation causes the dependence of drain current on the drain voltage in saturation. ECE 3040 - Dr. Ying Zhang Georgia Tech Recapture MOS Transistor Body Effect (Substrate Biasing) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ) ( 2qN ) ( 2qN where, devices) channel- p (for 2 2 devices) channel- n (for 2 2 S D S A devices channel p C devices channel n C V V Jaeger V Pierret V V V Jaeger V Pierret V ox ox F BS F TO TP T F BS F TO TN T = = + = = + = = This can be rewritten in the following form (more convenient to reference the threshold voltage to the V BS =0 case). is known as the body effect parameter ECE 3040 - Dr. Ying Zhang Georgia Tech Recapture Enhancement Mode versus Depletion Mode MOSFET ECE 3040 - Dr. Ying Zhang Georgia Tech Recapture MOS Transistor Summary NMOS PMOS Regardless of Mode Cutoff Linear Saturation Threshold Voltage V T for Enhancement Mode V T for Depletion Mode Pierret) in Z W : (Note ' = = = L W C L W K K ox n n n Pierret) in Z W : (Note ' = = = L W C L W K K ox n p p TN GS DS V v for i = TP SG DS V v for i = ( ) [ ] ( ) 1 2 2 + = TN GS DS DS TN...
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This note was uploaded on 09/05/2009 for the course ECE 3040 taught by Professor Hamblen during the Spring '07 term at Georgia Institute of Technology.

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Lecture22-MOS+TranSmallSigModelAmplifiers - ECE 3040 - Dr....

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