The IFFT program
The IFFT program analyzes linear circuits, computing transfer
functions in Laplace transform. From the transfer functions, in a
ratio-of-polynomials form, the program can compute poles and
zeros an plot frequency response graphs. The program was
developed as a tool for fast verification of continuous time
filter designs. It is also useful for other purposes, as:
- Stability analysis by direct poles and zeros calculation.
- Studies about frequency compensation of amplifiers.
- Studies about compensation of operational amplifier GB and input
and output impedance effects in filters.
- Studies about the effects of parasitic capacitances and
resistances in filters.
- Monte Carlo analysis and study of the effect of component
variations.
The EdFil editor is included in all versions. It provides easy
circuit entry in schematic form, requiring only a minimum of
information, typing, and care with the schematic layout
The use of the IFFT program is free for academic,
noncommercial purposes. For commercial use, please contact the
author.
Select a version to download below:
The files are compressed in the "zip" format.
- Windows version 1.7. Almost identical to version 1.6, for Windows.
- DOS version 1.6. Transformer
with "K".
- DOS version 1.5b. Accepts
operational amplifiers with 4 terminals (floating output) and comments.
Transconductors may have common-mode transconductance. (old)
- DOS version 1.4a. The most
tested version. Includes the EdFil editor and an utility to compute
time-domain responses by the inversion of the Laplace transform
(AnaTran). (old)
- Sun Unix version
1.0. Includes the executable IFFT and EdFil programs and the manual
file. (old)
- HP-UX version
1.0. Includes the executable IFFT and EdFil programs and the manual
file. (old)
- Linux version
1.0a. Requires X11 and XView. Included are the binary files for
IFFT and EDFIL and the manual. (old)
The DOS versions can be executed under varios operating systems
using the DOS emulator DosBox.
The picture above shows the simulation of an active filter realizing
a 5th-order elliptic filter. The frequency response is as expected, but
the structure has a natural frequency at zero, that appears as a
pole-zero cancellation there. This may be a problem in an actual
construction, because the circuit has undefined DC voltages or currents
somewhere on its structure.
Developed and Maintained by Antonio
Carlos M. de Queiroz
Last update: 2/7/2012.
Lamento informar que o Prof. Antonio Carlos Moreirão de Queiroz
faleceu há algum tempo.
Sei que esta página é visitada constantemente. Assim, gostaria de
saber se temos algum visitante (interessado) que seja da UFRJ. Se for,
por favor, envie um e-mail para watanabe@coe.ufrj.br.
Comento que é impressionante ver o que Moreirão foi capaz de fazer.
Ele não só projetou os circuitos, mas também fez todo o trabalho de
marceneiro (melhor que muitos que já vi e eram profissionais).
Segundo Moreirão contou em uma palestra, ele só levou choque uma vez.
Sem querer encostou o dedo médio em um capacitor com alta tensão que
se descarregou através do dedo. A corrente ao passar por uma das
articulações a danificou e doía sempre que dobrava esse dedo. Mas,
segundo ele, já tinha acostumado.
E. Watanabe (ELEPOT)