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Circuit Generation

In addition to FA, there is a program called CI that generates SPICE listings of active filters from a filter generated by FA. If in FA the command writesp is given, a file with the extension .ci is generated. So if the FA input file was called demo.in, the ci-file is called demo.ci. This file contains in order:

If, after this file has been generated and FA has ended, the command ci demo is issued, a file demo.cir will be generated. This file contains a SPICE listing of a filter circuit with idealized transconductances. The nature of the generated filter circuit can be modified if the realization command is added to the CI input file. This must be done after the capacitor specification and before the frequency specification, if present. The syntax of this command is
realization: <realization> ;
<realization> can be:
transconductor
opamp
opamp bandpass ( <ω0 >, <ωc > )
transconductor bandpass ( <ω0 >, <ωc > )
simple transconductor bandpass ( <ω0 >, <ωc > )
These specifications speak for themselves. transconductor is default. With the bandpass command, a capacitor-coupled-biquad bandpass filter with the specified filter as lowpass equivalent is generated. This might also be done by transforming the filter to a bandpass filter in FA, and generating the CI file afterwards. But then a transconductor or resistor-coupled filter is generated by CI, which in the case of bandpass filters usually is badly realizable, due to parasitic phase shift in the resistors. The CI bandpass specification works similar to the FA transform: bandpass() command.
next up previous contents
Next: A design example Up: Filter Analysis and Design Previous: Modification of do   Contents
2009-06-03