EE 435 Lect 4 Spring 2010

EE 435 Lect 4 Spring 2010 - EE 435 Lecture 4 Fully...

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1 EE 435 Lecture 4 Fully Differential Single-Stage Amplifier Design
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2 Design Space Exploration Question: How does the GB of the modified single-stage amplifier change with bias current? = EB DQ L V I C GB 2 3 2 OX DD DQ L CW P LV GB IC μ = 2 1 OX L DQ P GB CL I = Increases Linearly Increases Quadratically Decreases Linearly Decreases Quadradicly Independent of I DQ It depends upon how the design space is explored !!! OX DQ L 2 μ C W GB = I ⎡⎤ ⎢⎥ ⎣⎦ DD L EB 2P GB= VC V Review from last lecture:
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3 Design With the Basic Amplifier Structure Consider basic op amp structure V EB = -V SS -V T GB varies linearly with P ! GB is very costly ! If gain is adequate, designer got “lucky” but GB can be engineered { } EB P,V V0 EB 21 A = λ V ⎡⎤ ⎢⎥ ⎣⎦ DD L EB 2P GB= VC V Review from last lecture:
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4 Design space is often a high-dimensional system with many local extrema (minimums or maximums) Be careful about drawing conclusions about how any parameter individually affects system performance because its affect will depend upon how the design space is explored Review from last lecture:
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5 Design Space Exploration Different trajectories through a design space Note: After a device has been fabricated, often restricted on how varying of parameters can occur ! Review from last lecture:
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6 Multiple parameter domains can be used to characterize and explore a design space Performance characteristics of interest take on many different forms depending upon how design space is characterized Critical to identify the real number of degrees of freedom in design space (mathematical degrees of freedom minus the number of constraints) Performance characteristics often can be expressed as product of a process dependent term and an architecture dependent term Facilitates comparison of different architectures Choice of characterization parameters can make a major difference on how hard it is to explore a design space Review from last lecture:
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7 Basic Op Amp Design Fundamental Amplifier Design Issues Single-Stage Low Gain Op Amps Single-Stage High Gain Op Amps Two-Stage Op Amp Other Basic Gain Enhancement Approaches Where we are at: Review from last lecture:
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8 Single-Stage Low-Gain Op Amps Single-ended input Differential Input (Symbol does not distinguish between different amplifier types) Where we are at: Review from last lecture:
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9 Theorem: If a linear network is symmetric, then for all differential symmetric excitations, the small signal voltage is zero at all points on the axis of symmetry. Symmetric Networks V X d 2 V d 2 Review from last lecture:
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10 Theorem: Symmetric outputs of a symmetric network excited differentially have no common-mode components if biased at the axis of symmetry with an ideal current source.
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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 4 Spring 2010 - EE 435 Lecture 4 Fully...

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