Figure: PSpice model for the 741 op-amp
Simulate the integrator circuit of Figure 
using the 741 op-amp model
(see Figure ). Use the same resistor and capacitor values
as are shown in Figure .
Create an input voltage in PSpice identical to the integrator input voltage
as measured on the servo controller board in Section part .
Include the PSpice output, plots, and ``hand analysis (you may use an ideal
op-amp in the hand analysis)" in
your lab report.
Note that triangular, sawtooth, and square pulse waveforms can be created with:
Vname n+ n- PULSE(V1 V2 TD TR TF PW PER)
where V1 and V2 are the initial and pulsed voltage values respectively, TD is a time delay, TR and TF are rise and falls times, PW is the pulse width (time the voltage is at V2), and PER is the period of the pulse. There are several other source waveforms available in PSpice. These waveforms can be used for both voltage and current sources. Please refer to the PSpice tutorial in the EE61 Course-Pak.
In order to simulate the integrator using PSpice you will perform a transient analysis. To use transient analysis, include a .tran command line before the .op and .end lines. The structure of the .tran line is:
.tran <time step (s)> <time stop> <time start>
For example to run a simulation for 5 ms with 100 steps, you would issue the command:
.tran 50u 5m
Note that the default start time is zero if no value is in the code. In your simulation of the integrator circuit, you will find that it is necessary to plot the results for a time window that begins later than t=0 in order to obtain steady-state results. Try plotting voltages beginning at t=0 and you will see the necessity of plotting the voltages over a time interval that begins later than t=0. When you examine a plot of the voltage at the output of the op-amp beginning at t=0, you will observe a triangle wave superposed on an exponential. Try to explain this phenomenon.
The maximum number of steps on a PSpice plot is 200 (actually 201).
If
then you will need to utilize a .options control line. See the
Introduction to PSpice in the EE61 Course-Pak.