Download Transient Response

Transient Response
Transient Analysis
• Plot of the voltages or currents as a function of
time.
– Output plot mimics the oscilloscope display.
• If simulating the operation of a circuit that has a
sinusoidal source, you must select Vsin or Isin.
– Do NOT use Vac as the sinusoidal voltage source or Iac
as the sinusoidal current source.
• These are sinusoidal sources that should be used only when
running an AC Sweep simulation, where calculations are
performed as a function of the frequency of operation of the
voltage or current source, not as a function of time.
2
PSpice Schematic with LM324
Note (a) the orientation of the
negative and positive input
terminals, (b) the polarity of the
voltage sources tied to the V+ and
V- inputs on the op amp, and (c)
the placement of the voltage
markers.
Polarity of Voltage Sources
These two sources are the same.
Setting Attributes for Vsin
Vi = Vm sin(ωt ) + Vdc
Vi = 5V sin[3.24krad / s(t )]
where f = ω/2π
Double click on the Vsin symbol
highlighted in red on the
schematic.
Set:
VOFF (a d.c. offset voltage) to 0V
since there is no Vdc term in the
equation shown to the left.
VAMPL (the amplitude of the sine
wave) to Vm , which is 5V (or 5) in
this example,
FREQ (frequency, f, in Hertz – this
is not angular frequency) to ω/2π
- 1000Hz. 1kHz, 1000, or 1k.
5
Transient Analysis Set-up
Click on the Transient button located at the lower right of the Analysis Setup pop-up window.
Final Time
should be 3-5
times the period
(T) of V1.
T = 1/f where f
is the frequency
of the sinusoidal
signal.
Click on
to open the file that contains the plot.
You may have seen a count up of the time step (lower right) as the program go through the calculations as a
function of time. When done, Simulation complete should appear in the lower left . A plot will be generated where
the number of curves will be equal the number of voltage and current markers on the schematic.
Note that the curve displayed in this example is not quite sinusoidal.
To obtain a smoother sinusoid
In the Transient pop-up window,
set a Step Ceiling that is a small
fraction of the period of the
sinusoid that you are plotting.
Place voltage markers at Vsin and the output pin of the operational amplifier.
Plot of the input voltage and output
voltage as a function of time
Note that this plot is different from the ones that you will generate as the amplitude of the
input signal is higher and the op amp signal didn’t saturate.
Reading Data Off of a PSpice Graph
Cursors
• Click on the plot to activate
the cursors and move them
along the plot that has been
selected.
– The voltage and time of the
point on the curve where the
cursor is located is displayed
in the Probe Cursor pop-up
window.
• Click on the symbol next to
the plot name to change
which plot the cursors are
associated with.