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FUBOCO: Structure Synthesis of Basic Op-Amps by FUnctional BlOck COmposition

Inga Abel, Helmut Graeb

TL;DR

A method to automatically synthesize the structure and initial sizing of an operational amplifier and develops a hierarchical composition graph based on functional blocks that spans a search space of thousands of technically meaningful structure variants for single-output, fully differential, and complementary operational amplifiers.

Abstract

This paper presents a method to automatically synthesize the structure of an operational amplifier. It is positioned between approaches with fixed design plans and a small search space of structures and approaches with generic structural production rules and a large search space with technically impractical structures. The presented approach develops a hierarchical composition graph based on functional blocks that spans a search space of thousands of technically meaningful structure variants for single-output, fully-differential and complementary operational amplifiers. The search algorithm is a combined heuristic and enumerative process. The evaluation is based on circuit sizing with a library of behavioral equations of functional blocks. Formalizing the knowledge of functional blocks in op-amps for structural synthesis and sizing inherently reduces the search space and lessens the number of created topologies not fulfilling the specifications. Experimental results for the three op-amp classes are presented. An outlook how this method can be extended to multi-stage op-amps is given.

FUBOCO: Structure Synthesis of Basic Op-Amps by FUnctional BlOck COmposition

TL;DR

A method to automatically synthesize the structure and initial sizing of an operational amplifier and develops a hierarchical composition graph based on functional blocks that spans a search space of thousands of technically meaningful structure variants for single-output, fully differential, and complementary operational amplifiers.

Abstract

This paper presents a method to automatically synthesize the structure of an operational amplifier. It is positioned between approaches with fixed design plans and a small search space of structures and approaches with generic structural production rules and a large search space with technically impractical structures. The presented approach develops a hierarchical composition graph based on functional blocks that spans a search space of thousands of technically meaningful structure variants for single-output, fully-differential and complementary operational amplifiers. The search algorithm is a combined heuristic and enumerative process. The evaluation is based on circuit sizing with a library of behavioral equations of functional blocks. Formalizing the knowledge of functional blocks in op-amps for structural synthesis and sizing inherently reduces the search space and lessens the number of created topologies not fulfilling the specifications. Experimental results for the three op-amp classes are presented. An outlook how this method can be extended to multi-stage op-amps is given.

Paper Structure

This paper contains 31 sections, 4 equations, 10 figures, 5 tables, 4 algorithms.

Table of Contents

  1. Introduction
  2. Functional Blocks in Op-Amps
  3. Synthesis of Functional Blocks Except Op-Amp Bias
  4. Data Structure
  5. Generic Algorithm to Synthesize a Functional Block (Except Op-Amp Bias)
  6. Input
  7. Algorithm
  8. Synthesis of the Op-Amp Bias
  9. Structure of an Op-Amp Bias
  10. Generic Algorithm to Synthesize the Op-Amp Bias $b_O$
  11. FUnctional BlOck COmposition (FUBOCO) of a Complete Op-Amp Topology
  12. Hierarchy Level 1: Devices
  13. Hierarchy Level 2: Structures
  14. Hierarchy Level 3: Amplification Stage Subblocks
  15. Hierarchy Level 4: Amplification Stages
  16. ...and 16 more sections

Figures (10)

  • Figure 1: Hierarchical structure of functional blocks in op-amps
  • Figure 2: Example topologies synthesizable with the presented method, colored background: functional blocks of HL 2 - 4
  • Figure 3: Voltage bias instance and corresponding structural implementations
  • Figure 4: Input of Algorithm \ref{['algo:SynthesisFunctionalBlock']}, FB$_j$: $j$th functional block, $s_j$: a structural implementation of FB$_j$
  • Figure 5: Schematic overview of a bias
  • ...and 5 more figures