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Description:

ahkab 0.18

a SPICE-like electronic circuit simulator written in Python
The code should be easy to read and modify, the main language is Python
– 2 or 3 – and it is platform-independent.

News!

Ahkab v0.18 was released on July 18 2015, including new features,
bugfixes and improved documentation. It is recommended to upgrade.
Check out the release
notes for
more!
The whole codebase has been going through a (yet incomplete)
refactoring and documenting effort. The new documentation is
available on RTD.

My resources are limited these days, so the much-needed work is
proceeding slowly, albeit hopefully steadily. If you are interested and
you would like to contribute to refactoring or documenting a particular
feature, it would be very welcome.

Supported simulations:

Numeric:

Operating point, with guess computation to speed up the
solution. See example: Downscaling current
mirror
DC sweep
Transient analysis, available differentiation formulas:
implicit Euler, trapezoidal, gear orders from 2 to 5. See for
example the simulation of a Colpitts
Oscillator.
AC analysis
PZ analysis
Periodic steady state analysis of non-autonomous circuits,
time domain shooting and brute-force algorithms.

Symbolic:

Small signal analysis, AC or DC, with extraction of transfer
functions, DC gain, poles and zeros. Various symbolic analysis
examples on this
page.

The results are saved to disk, plotted or printed to stdout and can be
read/processed by the most common tools (eg.
Octave,
gnuplot,
Matlab,
gwave and others)

Install
The program requires:

the Python interpreter version 2 or 3 (at least v.2.6 for Python2,
v.3.3 for Python3),
numpy>=1.7.0, scipy>=0.14.0, sympy>=0.7.6 and tabulate>=0.7.3.

Matplotlib is strongly recommended and no plotting will work without.
If you need more information about the dependencies, check the Install
notes.

Usage

1. ahkab can be run as a Python library
from ahkab import new_ac, run
from ahkab.circuit import Circuit
from ahkab.plotting import plot_results # calls matplotlib for you
import numpy as np

# Define the circuit
cir = Circuit('Butterworth 1kHz band-pass filter')
cir.add_vsource('V1', 'n1', cir.gnd, dc_value=0., ac_value=1.)
cir.add_resistor('R1', 'n1', 'n2', 50.)
cir.add_inductor('L1', 'n2', 'n3', 0.245894)
cir.add_capacitor('C1', 'n3', 'n4', 1.03013e-07)
cir.add_inductor('L2', 'n4', cir.gnd, 9.83652e-05)
cir.add_capacitor('C2', 'n4', cir.gnd, 0.000257513)
cir.add_inductor('L3', 'n4', 'n5', 0.795775)
cir.add_capacitor('C3', 'n5', 'n6', 3.1831e-08)
cir.add_inductor('L4', 'n6', cir.gnd, 9.83652e-05)
cir.add_capacitor('C4', 'n6', cir.gnd, 0.000257513)
cir.add_capacitor('C5', 'n7', 'n8', 1.03013e-07)
cir.add_inductor('L5', 'n6', 'n7', 0.245894)
cir.add_resistor('R2', 'n8', cir.gnd, 50.)

# Define the analysis
ac1 = new_ac(2.*np.pi*.97e3, 2.*np.pi*1.03e3, 1e2, x0=None)

# run it
res = run(cir, ac1)

# plot the results
plot_results('5th order 1kHz Butterworth filter', [('|Vn8|',"")], res['ac'],
outfilename='bpf_transfer_fn.png')

2. ahkab can be run from the command line with a netlist file
The syntax is:
`$ python ahkab -o graph.dat <netlist file>`
See ahkab --help for command line switches, also online on the
documentation
pages.

Documentation
The documentation is available on
RTD.
There, you can find a
documentation
and
examples
regarding how to simulate from a Python script.
Refer to the netlist syntax
page
if you prefer to write netlist files that describe the circuit.
Experience with running SPICE or related commercial simulators can be
very useful: this is not for the faint of heart.

Development model

The development happens on the github
repository,
Mostly on the master branch, with feature branch being created only
for special purposes or non-trivial features.
Snapshots are released on a (hopefully) regular basis and are
available on the Releases pages, complete with
changelog and on
PYPI

Patches and pull requests are welcome!

How this project was born
This project was born when I was an enthusistic undergrad, apparently
with plenty of free time, attending “Simulazione Circuitale” (Circuit
Simulation) taught by Prof. A.
Brambilla back in Italy at the
Polytechnic University of Milan.
I am grateful to prof. Brambilla for teaching one of the most
interesting courses of my university years. -GV

Bugs and patches
Does it work? Bugs? Do you have patches? Did you run some noteworthy
simulation? Let me know! Feedback is very welcome, my email
address is available after a captcha.

Support the development with a donation
If you wish to support the development of ahkab, *please donate to
cancer research:*

Association for International Cancer Research
(eng),

or

Fond. IRCCS Istituto Nazionale dei Tumori
(it).

Credits
Authors: Giuseppe Venturini,
with contributions from Ian Daniher
and Rob Crowther.
Code: the module py3compat.py is (c) 2013 - the Jinja team.
Dependencies: many thanks to the authors of numpy, scipy,
sympy, matplotlib and tabulate!