Lecture34-MOS+Logic+Gate+Design2

Lecture34-MOS+Logic+Gate+Design2 - ECE 3040:...

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ECE 3040 - Dr. Ying Zhang Georgia Tech ECE 3040: Microelectronic Circuits Lecture 34 Reading: Jaeger 6.1-6.12, 7.1-7.4, Notes
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ECE 3040 - Dr. Ying Zhang Georgia Tech ± Body Effect for Saturated Load Inverter ± Noise Margins for Saturated Load Inverter ± NMOS Inverter with Depletion Load ± CMOS Inverter ± Other CMOS Logic Gates Agenda
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ECE 3040 - Dr. Ying Zhang Georgia Tech Since the substrate is common to both transistors, the body-to-source voltage, v SB , varies as the output voltage varies. Thus, the threshold voltage varies resulting in a variation in V OH () [] () [] F F OH TO DD OH F F SB TO DD OH L TN DD OH V V V V v V V V V V V φφ γ 2 2 2 2 + + = + + = = In writing the above equation we have only examined the condition when v SB =V OH . Since v SB =v O , the threshold voltage is continuously varying as the device is switched, introducing an additional level of “non-linearity” (v O =f(v O ) and i DS =f(v O ) ). Saturated Enhancement Load
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ECE 3040 - Dr. Ying Zhang Georgia Tech () [] () [] V or V V V V or V V V V V V V and V If OH OH OH OH OH F F OH TO DD OH F 64 . 5 39 . 3 0 1 . 19 03 . 9 6 . 0 6 . 0 5 . 0 1 5 2 2 6 . 0 2 5 . 0 2 = = + + + = + + = = = φφ γ φ Saturated Enhancement Load
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ECE 3040 - Dr. Ying Zhang Georgia Tech Saturated Enhancement Load Since the body effect changes V TN , we need to readjust the width to length ratios of both transistors: M S : V OH is lower than what we used before, so we need the same current at a lower voltage--make the switching transistor even wider! () () () 1 59 . 3 25 . 0 25 . 0 5 . 0 1 39 . 3 6 25 ... ... 6 50 5 . 0 2 ' = = = S S S DS S DS TN S GS S n S DS L W V V V V L W V A e A e v v V v L W K i
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ECE 3040 - Dr. Ying Zhang Georgia Tech Saturated Enhancement Load () () 39 . 3 1 07 . 1
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Lecture34-MOS+Logic+Gate+Design2 - ECE 3040:...

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