ppt-review2 voltage follower

Analysis and Characterization of Different Voltage Follower Topologies

Analysis and Characterization of Different Voltage Follower Topologies

Guided By:Prof. Vijay SavaniPrepared By:Jaymeen Aseem (09BEC003)Jay Padaliya (09BEC037)06-10-2012106-10-20122Project ReviewPhase-2Outline 06-10-20123Super Source Follower (0.5 m design)90 nm Technology IntroductionBasic Source FollowerFlipped Voltage FollowerThreshold Independent Voltage FollowerSource Coupled PairComparative Analysis of 90 nm DesignsConclusionReferencesSuper Source FollowerThe circuit uses negative feedback through M2 to reduce the output resistance.From dc standpoint, the bias current in M2 is difference between and

06-10-20124Circuit DiagramSchematic DiagramSuper Source Follower

4 > is required for the proper operation. The small signal equivalent circuit is shown below:

From figure,

06-10-20125Super Source FollowerSo, output resistance of source follower is reduced by factor Voltage headroom around output node is So a tradeoff between output swing and minimum supply voltage should be made.Super source follower is designed to have less power and area requirement than the basic source follower. But, it also has some limitations.The negative feedback loop through M2 may not be stable in all cases. So, non-linearities may be observed in transient analysis.

06-10-20126Super Source Follower

Transient Analysis


DC Analysis


AC Analysis


Simulation Results (For the Super Source Follower)ParameterValueOutput Voltage Swing0.8 Volts for 1 V pp inputPower Dissipation18.45 WOffset Voltage814.71 mVBandwidth656.37 MHzNo. of Transistors206-10-201210Super Source FollowerComparison Between Basic Source Follower and Super Source FollowerTopologyPower DissipationBandwidthVoltage GainOffset VoltageBasic Source Follower187.8 W37.218 MHz0.91.2022 VoltsSuper Source Follower18.45 W656.37 MHz0.80.814 Volts06-10-201211Comparison Between Various TopologiesTopologyOutput resistanceOutput SwingSource followerSuper source followerFlipped voltage followerThreshold Independent Voltage Follower

06-10-20121290 nm DesignWe have implemented four voltage follower designs in 0.5 m technology. Now, we will implement them in 90 nm technology using Mentor Graphics tool. We will analyze them by using pre-layout simulation.For 0.5 m technology, the minimum channel length is 0.5 m. While, for 90 nm design, it is 100 nm.With technology scaled down, the channel length and width are scaled down. Accordingly, the parameters like supply voltage, threshold voltage are also scaled down.The scaled parameters affect the characteristics of voltage follower design.The major difference is in the DC analysis. DC analysis shows the relationship between output voltage and input voltage.1306-10-2012For the 0.5 m design, the DC characteristics is linear in nature. But, for 90 nm design, it is somewhat non-linear (parabolic in nature).This is the major problem associated with the deep-submicron technologies design of voltage follower. As the technology is scaled down, the threshold voltage VT is not scaled down proportionally. So, this non-linear behavior of threshold voltage cause performance of design to deviate from ideal one.The supply voltage taken for 0.5 m design is 3.3 volts. For the 90 nm design, it is taken as 1.8 volts. 06-10-20121490 nm designVoltage Follower Topologies for 90 nm designFor 90 nm design, we consider three topologies:Basic Source FollowerFlipped Voltage FollowerThreshold Independent Voltage FollowerWe will analyze them by applying transient analysis, DC analysis and AC analysis.

06-10-201215Basic Source Follower


Transient Analysis


For the full output swing, we have to keep input current larger. This waveform is for 1000 A input current source. Previous waveform was for 10 A current source. But for larger current, the power dissipation is also larger.06-10-201218Basic Source Follower

18DC Analysis


AC Analysis06-10-201220Basic Source Follower

Simulation Results for Basic Source FollowerParameterValueOutput Voltage Swing1.95 Volts for 2 V pp inputPower Dissipation15.8 W (for 10 A current source)

203.57 W (for 100 A current source)Offset Voltage2.03 VoltsBandwidth55.6 GHzNo. of Transistors106-10-201221Basic Source Follower

Basic Source Follower using PMOS Load


Simulation Results for PMOS Load Basic Source Follower06-10-201223Basic Source Follower

ParameterValueOutput Voltage Swing1.85 Volts for 2 V pp inputPower Dissipation58.04 WOffset Voltage0.540 VoltsBandwidth44.05 GHzNo. of Transistors2Basic Source Follower using Current Mirror


Simulation Results for Current Mirror Based Basic Source FollowerParameterValueOutput Voltage Swing1.85 Volts for 2 V pp inputPower Dissipation17.04 WOffset Voltage0.294 VoltsBandwidth32.18 GHzNo. of Transistors306-10-201225Basic Source Follower

Difference for 500 nm and 90 nm designsDesignPower DissipationBandwidthOffset VoltageVoltage Swing500 nm187.8 W37.12 MHz1.2022 Volts0.9590 nm15.8 W32.5 GHz2.03 Volts0.906-10-201226Basic Source Follower The major difference is in the DC characteristics. The 90 nm design has non-linear transfer characteristics as compared to the 500 nm design. The power dissipation for 90 nm design is low. But the output voltage swing is limited. The bandwidth is also increased in 90 nm design.Flipped Voltage Follower

06-10-201227Flipped Voltage Follower

Transient Analysis06-10-201228Flipped Voltage Follower

DC Analysis06-10-201229Flipped Voltage Follower

AC Analysis06-10-201230Flipped Voltage Follower

Simulation Results for Flipped Voltage FollowerParameterValueOutput Voltage Swing1.8 Volts for 2V pp inputPower Dissipation10.04 WOffset voltage1.13 VoltsBandwidth5.8 GHzNo. of Transistors206-10-201231Flipped Voltage Follower

Difference Between 90 nm and 500 nm Designs06-10-201232Flipped Voltage FollowerDesignPower DissipationBandwidthOffset VoltageVoltage Swing500 nm14.4 W6.088 MHz1.86 Volts0.990 nm10.04 W5.8 GHz1.13 Volts0.932Threshold Independent Voltage Follower

06-10-201233Threshold Independent VFTransient Analysis06-10-201234Threshold Independent VF

DC Analysis06-10-201235Threshold Independent VF

AC Analysis06-10-201236Threshold Independent VF

Simulation Results for Threshold Independent VF using Ideal Current Source06-10-201237Threshold Independent VFParameterValueOutput Voltage Swing1.95 Volts for 2 V pp inputPower dissipation21.10 WOffset Voltage99.8 mVBandwidth8.5 GHzNo. of Transistors2Comparison of 90 nm design and 500 nm designs06-10-2012Threshold Independent VF38DesignPower DissipationBandwidthOffset VoltageVoltage Swing500 nm115.5 W34.52 MHz 55.72 mV0.9590 nm21.10 W 8.5 GHz 99.8 mV0.95Source Coupled Pair06-10-201239Source Coupled Pair

Transient Analysis06-10-201240Source Coupled Pair

DC Analysis06-10-2012Source Coupled Pair41

AC Analysis06-10-2012Source Coupled Pair42

Simulation Results for Source Coupled Pair Voltage Follower06-10-2012Source Coupled Pair43ParameterValueOutput Voltage Swing1.95 Volts for 2 V pp inputPower Dissipation48.27 WOffset Voltage2.33 mVBandwidth6.8 GHzNo. of Transistors2Comparative Analysis for 90 nm and 500 nm Designs06-10-2012Source Coupled Pair44DesignPower DissipationBandwidthOffset VoltageVoltage Swing500 nm99.88 W14.95 MHz9.09 mV0.97590 nm48.27 W7.8 GHz 2.33 mV0.95Future Work06-10-201245We have shown the pre-layout simulation of three topologies in 90 nm technology. We have also shown super source follower design in 500 nm technology.In next phase, we will implement the remaining designs in 90 nm technology with pre-layout simulation. Also, we will show the post-layout simulation of all topologies in 90 nm. We will analyze the pre-layout and post-layout simulation results for 90 nm technology.

Conclusion06-10-201246The voltage follower designs in 90 nm and 500 nm technologies give the different outputs. For 500 nm design, the transfer characteristic is linear in nature. While, for 90 nm it is non-linear.For 500 nm design, the power dissipation is high. The supply voltage requirement is also high.For 90 nm design, power dissipation is low. Supply voltage can be reduced from 3.3 V to 1.8 V or even further (up to 1.0 V).The area requirement for 90 nm design is obviously low compared to 500 nm design.References[1] Behzad Razavi, Design of Analog CMOS Integrated Circuits, McGraw-Hill publication, 2001. [2] P. E. Allen and D. R. Holberg, CMOS Analog Circuit Design, Oxford University Press, 2002.[3] Harry W. Li, R. Jacob Baker and David E. Boyce, CMOS Circuit Design, Layout and Simulation, IEEE Press Series on Microelectronics Systems, 2005.[4] Franco Maloberti, Analog Design for CMOS VLSI systems, Kluwer Academic/Plenum Press, 1998.[5] Yahoui Kong, Shuzheng Xu and Huazong Y, An Ultra Low Output Resistance and Wide Swing Voltage Follower, ICCCAS 2007, pp. 1007-1010, July 2007. [6] Carvajal R.G., Ramirez-Angulo J., Lopez-Martin A.J., Torralba A. Galan, J.A.G. Carlosena A. and Chavero F.M., The Flipped Voltage Follower: A Useful Cell for Low Voltage Low Power Circuit Design, IEEE circuits and systems, pp. 1276-1291, July 2005.[7] Gaurang P. Banker, Amisha P. Naik and N.M. Devashrayee, Comparative Analysis of Low Power CMOS Class-A Voltage Followers with Current Mirror as a Load, International Journal of Electronics and Communication Technology (IJECT), to appear in vol.2 Issue. 2, June 2011.

06-10-201247THANK YOU06-10-201248

ppt-review2 voltage follower

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