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VLSI System Design: DC & Transient Response

Understand the principles of DC and transient response in VLSI system design, covering transistor operation, current behavior, gate capacitance, and more. Activity tasks included.

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VLSI System Design: DC & Transient Response

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  1. VLSI System Design DC & Transient Response Engr. Noshina Shamir UET,Taxila

  2. Outline • DC Response • Logic Levels and Noise Margins • Transient Response • Delay Estimation 4: DC and Transient Response

  3. Activity 1)If the width of a transistor increases, the current will  increase decrease not change 2)If the length of a transistor increases, the current will increase decrease not change 3)If the supply voltage of a chip increases, the maximum transistor current will increase decrease not change 4)If the width of a transistor increases, its gate capacitance will increase decrease not change 5)If the length of a transistor increases, its gate capacitance will increase decrease not change 6)If the supply voltage of a chip increases, the gate capacitance of each transistor will increase decrease not change 4: DC and Transient Response

  4. Activity 1)If the width of a transistor increases, the current will  increase decrease not change 2)If the length of a transistor increases, the current will increase decrease not change 3)If the supply voltage of a chip increases, the maximum transistor current will increase decrease not change 4)If the width of a transistor increases, its gate capacitance will increase decrease not change 5)If the length of a transistor increases, its gate capacitance will increase decrease not change 6)If the supply voltage of a chip increases, the gate capacitance of each transistor will increase decrease not change 4: DC and Transient Response

  5. DC Response • DC Response: Vout vs. Vin for a gate • Ex: Inverter • When Vin = 0 -> Vout = VDD • When Vin = VDD -> Vout = 0 • In between, Vout depends on transistor size and current • By KCL, must settle such that Idsn = |Idsp| • We could solve equations • But graphical solution gives more insight 4: DC and Transient Response

  6. Transistor Operation • Current depends on region of transistor behavior • For what Vin and Vout are nMOS and pMOS in • Cutoff? • Linear? • Saturation? 4: DC and Transient Response

  7. nMOS Operation 4: DC and Transient Response

  8. nMOS Operation 4: DC and Transient Response

  9. nMOS Operation Vgsn = Vin Vdsn = Vout 4: DC and Transient Response

  10. nMOS Operation Vgsn = Vin Vdsn = Vout 4: DC and Transient Response

  11. pMOS Operation 4: DC and Transient Response

  12. pMOS Operation 4: DC and Transient Response

  13. pMOS Operation Vgsp = Vin - VDD Vdsp = Vout - VDD Vtp < 0 4: DC and Transient Response

  14. pMOS Operation Vgsp = Vin - VDD Vdsp = Vout - VDD Vtp < 0 4: DC and Transient Response

  15. I-V Characteristics • Make pMOS is wider than nMOS such that bn = bp 4: DC and Transient Response

  16. Current vs. Vout, Vin 4: DC and Transient Response

  17. Load Line Analysis • For a given Vin: • Plot Idsn, Idsp vs. Vout • Vout must be where |currents| are equal in 4: DC and Transient Response

  18. Load Line Analysis • Vin = 0 4: DC and Transient Response

  19. Load Line Analysis • Vin = 0.2VDD 4: DC and Transient Response

  20. Load Line Analysis • Vin = 0.4VDD 4: DC and Transient Response

  21. Load Line Analysis • Vin = 0.6VDD 4: DC and Transient Response

  22. Load Line Analysis • Vin = 0.8VDD 4: DC and Transient Response

  23. Load Line Analysis • Vin = VDD 4: DC and Transient Response

  24. Load Line Summary 4: DC and Transient Response

  25. DC Transfer Curve • Transcribe points onto Vin vs. Vout plot 4: DC and Transient Response

  26. Operating Regions • Revisit transistor operating regions 4: DC and Transient Response

  27. Operating Regions • Revisit transistor operating regions 4: DC and Transient Response

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