In most cases, the best way to specify the capacitances to FA is via the variable ctot that stands for the total capacitance value to be used for the whole filter. If FA runs into an analysis where it needs to know the capacitance values and ctot is not defined it issues an error message. By default the total capacitance ctot is divided equally over the capacitors of the filter. It is also possible to divide the capacitance optimally, see Section 10.4.2.
It is possible to specify the individual capacitances of the filter, for instance as follows.
caps = 1e-11 2e-11 3e-11 ;This example applies to a third-order filter, and the three capacitor values are 10pF, 20pF and 30pF, respectively. Upon specification of the capacitor values in this way, FA will automatically adjust the value of ctot.
Setting the evalc will automatically redistribute the total capacitance, dependent on the status of the eqc and optc flags. If eqc is set, the capacitance will be redistributed equally. If optc, it will be distributed optimally. Specifying the capacitors individually will automatically clear the evalc flag.