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Chapter 9 Graphs, Probes and Data Analysis
You do not need to make any decisions on how you wish to probe your circuit before
starting the run. You can enter a circuit without any fixed probes, run it, then randomly
probe afterwards. Alternatively, you can place a single fixed probe on an obvious point
of interest, then randomly probe to investigate the detailed behaviour of your circuit.
Note that you can add fixed probes after a run has started but the run must be paused
first.
There are currently 9 types of fixed probe to suit a range of applications. The random
probing method allows you to plot anything you like including device power, FFTs,
arbitrary expressions of simulation results and X-Y plots such as Nyquist diagrams. It
is possible to set up fixed probes to plot arbitrary expressions of signals but this
requires manually entering the underlying simulator command, the .GRAPH control.
There is no direct schematic support for this. For more info on the .GRAPH control see
the “Command Reference Chapter” of the Simulator Reference Manual.
Fixed Probes
There are 9 types of fixed probe as described in the following table
Probe Type
Description
To Place
Voltage
Single ended voltage. Hint: If Menu: Probe|Place Fixed
Voltage Probe...
you place the probe
immediately on an existing
Hot key: B
schematic wire, it will
automatically be given a
meaningful name related to
what it is connected to
Current
Device pin current. A single Menu: Probe|Place Fixed
terminal device to place over Current Probe...
a device pin
Hot key: U
Inline current
In line current. This is a two Menu: Probe|Place Inline
Current Probe...
terminal device that probes
the current flowing through it.
Differential voltage Probe voltage between two
points
Menu: Probe|Place Fixed
dB
Menu: Probe AC/Noise|Fixed
Probes db value of signal
voltage. Only useful in AC
analysis
Diff. Voltage Probe...
dB Probe...
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