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2.10 Nonlinear Symbolic Approximation 169
CancelTerms returns the simplified DAEObject. All nonlinear options which are stored in dae
are copied to the new system. Thus, the returned system can be used as input for subsequent
simplifications.
By default, CancelTerms removes terms in top-level sums of the equation system. Using the option
Level, removal of terms can be performed in deeper levels, too. The value of this option is either
a non-negative integer, a list of non-negative integers, or the symbol All. For the latter, removal of
terms is performed in all levels, starting on top level.
2.10.2 Analyzing a Square Root Function Block
In this section the application of the nonlinear simplification functions is demonstrated on an
example. Figure 10.1 shows the schematic of a nonlinear square root function block consisting of
four bipolar transistors.
I0
Q3
VLOAD
VCC
Q1
Q2
5
Q4
II
Figure 10.1: Square root function block
The input is given by the current source II and the voltage source VLOAD, the output is given by the
current through the voltage source VLOAD. Using the nonlinear approximation routines we want to
generate a symbolic expression for the static input output behavior of the circuit.
Importing Numerical Data
In PSpice the numerical simulation is performed as a DC sweep on ii and vload. The corresponding
part of the .cir-file looks as follows:
.op
.dc ii 0.0 0.001 0.00001 vload 0 3.5 0.875
.probe/csdf
.options numdgt=8