DC circuits

In the circuit shown in the figure, $i_1=1\,$mA. Find $g_m$. Also, calculate $V_A$, $V_B$, $V_C$ (with node 0 taken as $0\,$V), $I_{R2}$, $I_{R3}$, $I_{R4}$, and verify with simulation results.

from IPython.display import Image
Image(filename =r'dc_circuit_10_fig_1.png', width=350)

# run this cell to view the circuit file.
%pycat dc_circuit_10_orig.in

We now replace the string \$gm with the value of our choice by running the python script given below. It takes an existing circuit file dc_circuit_10_orig.in and produces a new circuit file dc_circuit_10.in, after replacing \$gm with the value of our choice.

import gseim_calc as calc
s_gm = '2m' # to be changed by user
l = [
  ('$gm', s_gm),
]
calc.replace_strings_1("dc_circuit_10_orig.in", "dc_circuit_10.in", l)
print('dc_circuit_10.in is ready for execution')

dc_circuit_10.in is ready for execution

Execute the following cell to run GSEIM on dc_circuit_10.in.

import os
import dos_unix
# uncomment for windows:
#dos_unix.d2u("dc_circuit_10.in")
os.system('run_gseim dc_circuit_10.in')

Circuit: filename = dc_circuit_10.in
main: i_solve = 0
GSEIM: Program completed.

0

The circuit file (dc_circuit_10.in) is created in the same directory as that used for launching Jupyter notebook. The last step (i.e., running GSEIM on dc_circuit_10.in) creates the data file dc_circuit_10.dat in the same directory. We can now use the python code below to compute and display the quantities of interest.

import numpy as np
import gseim_calc as calc

slv = calc.slv("dc_circuit_10.in")

i_slv = 0
i_out = 0
filename = slv.l_filename_all[i_slv][i_out]
print('filename:', filename)
u = np.loadtxt(filename)
VA = slv.get_scalar_double(i_slv, i_out, "VA", u)
VB = slv.get_scalar_double(i_slv, i_out, "VB", u)
VC = slv.get_scalar_double(i_slv, i_out, "VC", u)
IR1 = slv.get_scalar_double(i_slv, i_out, "IR1", u)
IR2 = slv.get_scalar_double(i_slv, i_out, "IR2", u)
IR3 = slv.get_scalar_double(i_slv, i_out, "IR3", u)
IR4 = slv.get_scalar_double(i_slv, i_out, "IR4", u)

s_format = "%7.2f"

calc.print_double_1('VA', VA, s_format)
calc.print_double_1('VB', VB, s_format)
calc.print_double_1('VC', VC, s_format)

s_format_1 = "%11.4E"

calc.print_double_1('IR1', IR1, s_format_1)
calc.print_double_1('IR2', IR2, s_format_1)
calc.print_double_1('IR3', IR3, s_format_1)
calc.print_double_1('IR4', IR4, s_format_1)

filename: dc_circuit_10.dat
VA:    6.48
VB:    0.48
VC:    1.35
IR1:  6.4758E-04
IR2: -7.2687E-04
IR3:  7.9295E-05
IR4:  2.2467E-04

This notebook was contributed by Prof. M. B. Patil, IIT Bombay. He may be contacted at mbpatil@ee.iitb.ac.in.