Post on 11-Nov-2020
INF3410 — Fall 2016
Excerpt of Sedra/Smith Chapter 7: Integrated CMOSAmplifiers Basics
Content
Bias Current Steering (book 7.2)
CS, CG, and cascode configuration (book 7.3-7.5)
Improved Current Mirrors/Sources (book 7.6)
Excerpt of Sedra/Smith Chapter 7: Integrated CMOSAmplifiers Basics 2
Content
Bias Current Steering (book 7.2)
CS, CG, and cascode configuration (book 7.3-7.5)
Improved Current Mirrors/Sources (book 7.6)
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CMOS Current Steering
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Dynamic Input Currents, Current Amplifier
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Content
Bias Current Steering (book 7.2)
CS, CG, and cascode configuration (book 7.3-7.5)
Improved Current Mirrors/Sources (book 7.6)
Excerpt of Sedra/Smith Chapter 7: Integrated CMOSAmplifiers Basics 6
Intrinsic Gain from Small Signal
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Intrinsic Gain vs Bias Current
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CS Amplifier with Current-Source Load
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CS Amplifier Analysis
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Home Assignment last week: Inverter SmallSignal Analysis
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CG amplifier revisited
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Rin of a CG amplifier
vx = (ix + gmvgs)ro + ixRLExcerpt of Sedra/Smith Chapter 7: Integrated CMOSAmplifiers Basics 13
Rout of a CG amplifier
vx = (ix − gmvgs)ro + ixRLExcerpt of Sedra/Smith Chapter 7: Integrated CMOSAmplifiers Basics 14
CS with source degeneration no RL
RO ≈ (1+ gmRS)ro
gm→ g′m =gm
1+ gmRsNo net-increase in gain!
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CS with source degeneration with RL
Av = g′mRORL
RL +RO
≈ gmroRL
RL + (1+ gmRS)ro
... and more degradation to Av due toload RL!
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Cascode Amplifier
Can be looked upon as a CS and CG in series where theCS serves as high quality voltage controlled currentsource delivering id ≈ gm1vi and the CG buffers thatcurrent to a high output resistance ≈ gm2ro2ro1.
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Cascode Amplifier with Infinite LoadResistance
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Folded Cascode with Infinite Load Resistance
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Cascode Amplifier with Finite LoadResistance (1/2)
The load RL must be of equal magnitude as RO to getthe benefit of the increased gain AV! So here with asimple pFET we are back to square one.
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Cascode Amplifier with Finite LoadResistance (2/2)
Better: employ a cascoded current source.
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Content
Bias Current Steering (book 7.2)
CS, CG, and cascode configuration (book 7.3-7.5)
Improved Current Mirrors/Sources (book 7.6)
Excerpt of Sedra/Smith Chapter 7: Integrated CMOSAmplifiers Basics 22
Cascode Current Mirror
Increased output impedance, but quite a bit of outputvoltage headromm necessary ...
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Modified Wilson MOS Current Mirror
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A CD-CS Amplifier
Larger bandwidth than simple CSamplifier (explained later in chapter 9).
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