EE 435 Lect 5 Spring 2010

EE 435 Lect 5 Spring 2010 - EE 435 Lecture 5 Spring 2010...

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1 EE 435 Lecture 5 Spring 2010 Fully Differential Single-Stage Amplifier Design Common-mode operation Slew Rate The Reference Op Amp
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2 Synthesis of fully-differential op amps from symmetric networks and counterpart networks Theorem: If F is any network with a single input and P is its counterpart network, then the following circuits are fully differential circuits --- “op amps”. 2 1 d V V V = OUT + V OUT V d 2 V d 2 OUT + V OUT V d 2 d 2 Review from last lecture:
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3 Synthesis of fully-differential op amps from symmetric networks and counterpart networks Terminology Quarter Circuit Counterpart Circuit Half Circuit 2 1 d V V V = OUT + V OUT V d 2 V d 2 Review from last lecture:
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4 Synthesis of fully-differential op amps from symmetric networks and counterpart networks A fully differential op amp is derived from any quarter circuit by combining it with its counterpart to obtain a half-circuit, combining two half-circuits to form a differential symmetric circuit and then biasing the symmetric differential circuit on the axis of symmetry . Quarter Circuit Further, most of the properties of the operational amplifier can be obtained by inspection, from those of the quarter circuit. Implications: Much Op Amp design can be reduced to designing much simpler quarter-circuits where it is much easier to get insight into circuit performance Review from last lecture:
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5 Determination of op amp characteristics from quarter circuit characteristics Note: Factor of 4 reduction of gain () L M1 L 2 1 2 1 M1 VO 2C G GB C G G BW G G 2 G A = + = + = G G A M VOQC = L M C G GB = L C G BW = Small signal Quarter Circuit Small signal differential amplifier Review from last lecture:
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6 Comparison of Tail Voltage and Tail Current Source Structures Small signal half-circuits are identical so voltage gains, BW, and GB are all the same OUT + V OUT V d 2 V d 2 OUT + V OUT V d 2 d 2 Review from last lecture:
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7 Single-stage low-gain differential op amp Quarter Circuit Need a CMFB circuit to establish V b1 V SS 3 1 1 2 O O L m g g sC g ) s ( A + + = O3 O1 m1 O g g 2 g A + = L m1 2C g GB = Single-Ended Output : Differential Input Gain Review from last lecture:
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8 Common-Mode and Differential-Mode Analysis Extension to differential outputs and symmetric circuits A B V 1 V 2 V OUT Theorem: The symmetric differential output voltage for any symmetric linear network excited at symmetric nodes can be expressed as OUT d d =A VV where A d is the differential voltage gain and the voltage V d = V 1 - V 2 Differential Output Symmetric Circuit with Symmetric Differential Output Theorem:
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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 5 Spring 2010 - EE 435 Lecture 5 Spring 2010...

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