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Use of PSPice Schematics to simulate an Inverting Amplifier
 | Get to the PSPice Schematics editor (see first step in exercise # 1) |
| Hit <Ctrl G> to get a part. Enter the part name ua741 (for Op. Amp m A741).
Add resistors (R), power supply (vdc), ground (agnd), and a sinusoidal source
(vsin) to construct the inverting amplifier circuit as shown below. In order to
designate the input and output terminals, get parts from the library called bubble
(again <Ctrl G> and type bubble). Stick one bubble at the input and another at
the output. |
| Double click on the resistors R1 to get to the attribute dialog box to set 100kW for
the feedback resistance, and 20kW for the input resistance R2.
This will provide a
voltage gain of (-100/20=-5). |
| Double click on the power supply (vdc) to set a value of 15V. |
| Double click on the bubble terminals and name them. It may be convenient to name
the input bubble as input, and the output bubble as output. |
| Double click on the sinusoidal source to get to the attribute dialog box. Enter the
following parameters and click on OK: |
| Amplitude 1V |
| Frequency 1KHz |
Note: The period of the sinusoidal source, T= 1/f= 1ms. For the sake of
simulation, we may need to display few cycles from the input and output
waveforms. Considering that five cycles is to be displayed, this will require
simulation time of 5ms. PSPice requires that you set time increments (called
steps) until you get to the end of the simulation ( time stop). Choosing a large
number of simulation points may require longer time and more memory to
store the data. Considering 1000 points for simulation, the time step in this
case will be 5ms/1000= 5us.
| From the Analysis at the top bar menu, select setup, then select transient.
Set
time stop by 5m and time step 5u, click on OK. The details of this step are shown
below.
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| To simulate, hit <F11>. The program will automatically run a subprogram for
graphics interface, called Probe. This will look like: |
| From the top bar menu, select Trace, click on Add, and name the trace and
input. You can also Navigate to get any voltage or current in the circuit. |
| From the top bar menu, click on Plot, then Add, to add a plot. Again go to
Trace, click on add, to add a trace for this new plot. Either you use Navigate
to get the output, or type the output name according the bubble title (output).
This will look like: |
Note that the voltage gain( as shown by the output probe is 5). The output is out of
phase with the input.
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