Page 56 - DCAP601_SIMULATION_AND_MODELING

Simulation and Modelling

Notes There is another refinement which should be made in our computation. The losses for the entire
current month were computed on the basis of the volume in storage at the end of last month. If
a large change in volume takes place between two consecutive time steps, this would lead to
errors. This could be corrected by first finding a temporary value of VOL (m) on the basis of
given VOL (m – I) (as usual) and then recalculating the losses on the basis of the average value
of the two volumes.

VOL(m) + VOL(m – l)
2

3.3 Analog and Digital Simulation

The simulations will be performed using the commercial software, “Electronics Workbench”,
which is mounted on the laboratory computers. With some research before the lab, you should
be able to do both an analog and a digital simulation. The simulations execute the circuits in
software and all voltages, currents, and waveforms can be scrutinized and printed out.

The circuits are entered by graphic capture, i.e. you draw the circuit on the computer screen by
putting the parts and linking them with wires. Once the circuit is entered, an investigation is
run. There are numerous kinds of analyses including DC conditions, small signal transfer
functions, and digital logic states for the case of digital circuits.

Analog Simulation

The analog simulation circuit will be the difference amplifier from the difference amplifier lab.
Before the lab organize a table of of the measured and computed DC node voltages, the sum and
difference gains, CMRR, and the amplifier high and low roll-off frequencies. You should have
approximately all this information in your laboratory notebook. The simulated circuit should
have the same constituent values used in the lab circuit. The consequences of the simulation
should then be entered as a separate column in your table.
1. Simulate the difference amplifier circuit by means of the circuit you built for the Difference
Amplifier lab. The constituent values should be indistinguishable to those used in the lab.
We use the Electronics Workbench application.
2. The first step is to make a schematic diagram.
3. Perform a DC analysis. Check the results against the expected values.
4. Execute a Transient analysis for 5 cycles and compute the difference and common mode
gains. Use the same frequency as you used in the lab. Use the investigation Graphs window
to print out the desired waveforms.

5. Execute a frequency analysis and establish the low and high rolloff frequencies. Print out
the Bode plot using the Analysis Graphs window.
6. Present the consequences as a three column table: theory, measurement, and simulation
for the requested quantities. Most people did not calculate the frequency dependence in
lab, but you should be able to evaluate the roll-off frequencies.
7. The final consequences will include the table, a copy of the circuit diagram, waveforms,
and your explanations as to why the simulation might be providing different results from
theory and measurement.

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