eldo_user

Optimization
Optimization in Eldo
Optimization in Eldo
Eldo contains a general-purpose electrical circuit optimization tool that simultaneously
improves AC, DC, Transient domain, Steady-State, and Modulated Steady-State analyses.
With each run of the optimizer, the adjustable component parameters of the circuit (the design
variables, see “Design Variables” on page 594) are modified in an attempt to reach desired
performance (the design objectives, see “Design Objectives” on page 603). The parameters
relating to the specified electrical performance are extracted and measured (the extracted
measures) to verify whether the desired performance has been met.
The design variables must conform to manufacturing limits, process limits, or discrete device
values (known as constraints). For example, they must be non-negative, or must not violate
upper boundaries. Restrictions and/or inter-relations can also be specified, for example, how
components physically interact with each other to produce non-linear relations.
The process of identifying the design objectives, design variables, and constraints for a specific
problem is known as modeling. The construction of an appropriate model is the first step in the
optimization process. If the model is too simplistic, it will not generate useful insights into the
practical problems. If too complex, it may become difficult to solve.
The optimizer output shows if the target performance (design objectives) has been reached, and
whether it might be possible to improve on the current solution. It also details the values of the
design variables, extracted measures, and constraints for each run.
Optimization Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 589
Optimization Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 591
Eldo Optimization Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 592
Optimization Commands
The definition of the design variables, the design objectives and the constraints, along with the
request for optimization, are all specified in the netlist file using simple extensions of the Eldo
commands. The links open the Simulator Commands chapter in the Eldo Reference Manual.
The .PARAMOPT command specifies the design variables and the constraints on them. The
syntax is:
.PARAMOPT VARIABLE_NAME=(
+ [INIT_VALUE,]
+ {LOWER_BOUND | LOWER_PERCENT% },
+ {UPPER_BOUND | UPPER_PERCENT% }
+ [, INCREMENT])
In the following example the .PARAMOPT command is used to specify the optimization
variables, the length l and the width w of a MOS transistor:
Eldo® User's Manual, 15.3 589