eldo_user

Optimization
Types of Design Objective
Related Topics
Minimization and Maximization Objectives
Goal Values Objectives
Objectives for Operating Modes
Objectives for Operating Modes
You can optimize the operating mode of transistors and bipolars in your circuit. The syntax of a
single statement is given as follows:
* OPMODE constraint statement
.OBJECTIVE EXTRACT_INFO LABEL=f_op
+ OPMODE(DEVICE_NAME)
+ GOAL=OPMODE_NAME
The goal is not specified as a value, it is a string. The different modes are recalled here:
• GOAL=SATURATION (MOS and BJT)
• GOAL=LINEAR (MOS and BJT)
• GOAL=ON (only BJT)
• GOAL=OFF (only BJT)
• GOAL=SUBTHRESHOLD (only MOS)
For a transistor, these modes can be expressed as numerical relations (constraints) between the
voltages VGS, VT, VDS, and VDSAT. For example, the LINEAR mode is characterized with the
two following constraints: VGS ≥ VT and VDS ≤ VDSAT. The same applies to the other modes.
There is no “goal value” for this objective, it is attempted to find a feasible configuration which
satisfies the OPMODE constraints. It is very likely that there is an infinite number of circuits
which are feasible. This means you must introduce additional objectives to optimize the circuit,
the role of these constraints is to force the circuit into a good operation mode.
Consider the following inverter example, the two transistors are “symmetric,” and must be
mutually in opposite configuration or state (linear and subthreshold):
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Eldo® User's Manual, 15.3