EE 435 Lect 9 Spring 2010

EE 435 Lect 9 Spring 2010 - EE 435 Lecture 9: High-Gain...

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1 EE 435 Lecture 9: High-Gain Single-Stage Op Amps - Regulated Folded Cascode Op Amp - Current-mirror op amps - OTA Applications
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2 Textbook reference: Some of the material we have been discussing appears in Chapter 3, some in Chapter 5, and some in Chapter 6 of the Martin and Johns text In particular, the telescopic and folded cascode structures are referred to as advanced op amps and appear in later chapters of the text
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3 What circuit is this? B1 1 3 OUT BB IN SS Folded Cascode Amplifier V DD V IN M 1 M 3 V B1 I B1 I B2 V OUT V SS Biased Folded Cascode Review from Last Time
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4 Folded Cascode Op Amp ± Needs CMFB Circuit for V B4 ± Either single-ended or differential outputs ± Can connect counterpart as current mirror to eliminate CMFB ± Folding caused modest deterioration of A V0 and GB energy efficiency ± Modest improvement in output swing Review from Last Time
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5 Folded Gain-boosted Telescopic Cascode Op Amp ± Needs CMFB Circuit for V B4 ± Either single-ended or differential outputs ± Can connect counterpart as current mirror to eliminate CMFB ± Folding caused modest deterioration in GB efficiency and gain ± Modest improvement in output swing L m1 2C g GB = () m9 1 o9 o7 m3 3 o3 O5 O1 m1 o g A g g g A g g g 2 g A + + V I N V I N V DD V S S I T V B4 M 1 M 2 M 7 M 9 M 1 0 M 5 M 6 M 3 M 4 V OU T C L V IN V B2 V B3 V S S I T2 M 8 V B1 A 1 A 2 A 3 A 4 Review from Last Time
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6 Operational Amplifier Structure Comparison Reference Op Amp Telescopic Cascode Regulated Cascode Folded Cascode Folded Regulated Cascode 3 1 1 2 1 O O m VO g g g A + = L m C g GB 2 1 = Small Signal Parameter Domain L T C I SR 2 = L T C I SR 2 = m5 o5 o7 m3 o3 o1 m1 o g g g g g g 2 g A + = L m C g GB 2 1 = 3 m9 o9 o7 1 m3 o3 o1 m1 o A g g g A g g g 2 g A + L m C g GB 2 1 = L T C I SR 2 = () m9 o9 o7 m3 o3 o5 o1 m1 o g g g g g g g 2 g A + + = L m C g GB 2 1 = L T C I SR 2 = () 9 m9 o9 o7 3 m3 o3 o5 o1 m1 o A g g g A g g g g 2 g A + + = L m C g GB 2 1 = L T C I SR 2 = Review from Last Time
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7 Summary of Folded Amplifier Performance + Modest improvement in output signal swing (from 5 V DS SAT to 4V DS SAT ) - Deterioration in A V0 (maybe 30% or more) - Deterioration in GB power efficiency (can be significant) - Minor increase in circuit size Review from Last Time
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8 Folded Gain-boosted Cascode Amplifier ± with ideal current source bias ± modest improvement in output swing L m1 2C g GB = () m3 o3 o1 m1 o g A g g g A
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9 Folded Gain-boosted Cascode Amplifier () A g g g g sC g V V m3 o3 o5 o1 L m1 IN OUT + + modest improvement in output swing L m1 C g GB = () o3 o5 o1 m3 m1 0 g g g A g g A +
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10 Basic Amplifier Structure Comparisons L m1 C g GB = o3 m3 O1 m1 VO g g g g A = Common Source Cascode Regulated Cascode Folded Cascode Folded Regulated Cascode O m VO g g A = L m C g GB = Small Signal Parameter Domain A g g g g A o3 m3 O1 m1 VO L m1 C g GB = () o3 m3 O5 O1 m1 VO g g g g g A + = L m1 C g GB = () A g g g g g A o3 m3 O5 O1 m1 VO + = L m1 C g GB =
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This note was uploaded on 01/31/2012 for the course EE 345 taught by Professor Geiger during the Fall '11 term at Iowa State.

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EE 435 Lect 9 Spring 2010 - EE 435 Lecture 9: High-Gain...

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