1. Cristian Ferent and Alex Doboli
Towards Creative Analog Synthesis: A Symbolic Representation for Exploring Circuit Operation Principles
Cristian Ferent and Alex Doboli
Department of Electrical and Computer Engineering
State University of New York at Stony Brook

2. Motivation, Goals, and Contributions
Systematically characterize a collection of designs:
Implement performance specific circuit models
Highlight common & different features between circuits
Identify advantages & limitations of a circuit compared to others
Derive conditions under which design alternatives exhibit similar performance

3. Motivation, Goals, and Contributions (II)
Model to characterize transconductor linearity
Illustrate mechanisms which can enhance circuit performance: extended operating range and/or device non-linearity compensation

4. Motivation, Goals, and Contributions (III)
Automatically produce circuit classification schemes:
Build a representation to express main similarities & differences between a set of circuits implementing the same functionality
Based on topological structures of features that influence the performance of a design
Produce compact classification – minimum of separation criteria

5. Problem Description: concept representation
[1]
Coupling between nodes
Classification along curve D1
Features related to performance
Circuit node
Similar node features
Distinguishing criteria curves
[1] C. Ferent, A. Doboli, "A Symbolic Technique for Automated Characterization of the Uniqueness and Similarity of Analog Circuit Design Features", DATE 2011

6. Proposed Method: automated generation of classification schemes
Produce the separation criteria for a given performance
Determine best separation criteria
Construct hierarchical classification scheme

7. Algorithm Details Build performance-based circuit models
2) Group nodes with similar behavior (separation criteria):
Minimize total number of matched groups (N )
Minimize matching error within groups of nodes
Identify constraints under which matching is valid

8. Algorithm Details (II)
3) Sort matched groups (cluster):
Signal path tracing and model decoupling algorithms
4) Use entropy to rank similarities and differences between circuits:
N – number of circuits represented in cluster Ck
pi – probability a circuit from cluster Ck is associated with matched group Gj
5) Produce hierarchy with maximum matching at higher levels

9. Similar behavior / topology Distinct behavior / topology
Frequency Domain Model Matching: amplifier circuits hierarchical classification
Increasing entropy
value
Similar behavior / topology
Distinct behavior / topology
Common structures
Different structures

10. Classification correlation with performance
Also identify number of terms that differ between node structures
Indication of topology’s flexibility to satisfy performance (e.g. setting pole and zero positions)

11. Transconductor Linearity Models
Extend range
Correct linearity

12. Linearity Model Matching: transconductors hierarchical classification
Common structures
Identical Processing Path
Additional Processing
Different structures

13. Identical Control Path Additional Control Voltages
Linearity Model Matching: (II) transconductors hierarchical classification
Identical Control Path
Additional Control
Additional Control Voltages

14. Future Work
Apply the proposed methodology for a set of state-of-the-art amplifier designs
Derive topological and performance classification schemes

15. Summary & Conclusions
Develop new symbolic technique for automated generation of circuit classification schemes
Produce the set of separation criteria
Based on performance specific circuit models
Sort separation criteria based on their capability to distinguish between different structures
Proposed metric based on entropy
Build hierarchical classification
Highlight similarities and differences with impact on performance
Offer insight through symbolic expressions
Identify common & dissimilar circuit node structures
Relate symbolic differences and similarities to performance attributes
Suggest design’s flexibility for achieving certain performance