Systematic Offset Detection and Evaluation Using Hierarchical Graph-Based Sizing and Biasing

A hierarchical graph-based sizing and biasing method of analog circuits has been previously developed. However, conflicts appear in dependency graphs generated by our method due to the large number of degrees of freedom in analog design. Therefore, an enhanced method is presented that automatically detects conflicts and resolves them by inserting systematic offset voltages as additional degrees of freedom into the graph. During graph evaluation, a systematic offset is evaluated as the voltage difference between conflicting nodes, which can be eliminated by transposing it to the inputs of the circuit. As an example, we have successfully applied our method to the sizing of a single-ended two-stage operational amplifier.