EECS 413 Design Project Design of a 90db CMOS differential amplifier with gainboosting and common mo

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EECS 413 Design ProjectDesign of a 90db CMOS
differential amplifier with gain-boosting and
common mode feedback

• Jimmy Yu
• Gary Sun
• Matt Ng

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OVERVIEW

• Applications
• Operational Amplifier Architecture
• Topology
• Resistance gainboosting
• Cascode Usage
• Common-mode feedback design
• Frequency considerations
• Simulation Results
• Conclusion

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USAGE AND APPLICATION

• Speed and accuracy determined by settling
  behavior of opamps
• Our amp will find uses in
• SC Filters
• Signal-processing functions
• Algorithmic A/D Converters
• Sigma-Delta Converters
• Sum-difference approach to A/D conversion
• Sample-and-hold Amplifiers
• Holds input at output when given hold signal
• Pipeline A/D Converters

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TOPOLOGY
OpAmp Block Diagram
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RESISTANCE BOOSTING

• Folded Cascoded Differential to Single-ended
  Amplifier.
• Utilized to increase the resistance seen by the
  output.

Figure 1
Figure 2
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CASCODING

• Differential Amp Cascoding
• Utilizes gain boosting technique to increase Rout
  seen by diff. amp
• Uses NMOS and PMOS load to maximize load

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COMMON MODE FEEDBACK

• Provides Better Linearity
• Greater Stability
• Output Vcm set by circuit

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CMFB (contd)

• Advantages
• Good linearity
• Large sensitivity to Vcm
• Small parasitic capacitance
• Disadvantages
• Large power consumption
• Large chip area

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FREQUENCY CONSIDERATIONS

• Dominant pole from output node
• Load capacitance and high resistance
• Phase Margin of 60
• Push other poles and zeroes past unity gain
  frequency
• Unity Gain of 300 MHz
• wu gm/CL

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SIMULATION RESULTS
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CONCLUSION

• Can achieve extremely high gain through
• Folded load network
• Cascoding
• Gain-boost technique
• Large unity-gain frequency can be attained via
• Sizing