User`s guide

18
-
2 Viewin
g
Results on the Schematic
Viewin
g
Bias Point
Volta
g
es
and Currents
After simulating, you can display bias point information on your
schematic so you can find problem areas in your design.
How it works
When simulating, PSpice A/D calculates and saves the bias
point voltages and currents. By default, Schematics reads all of
this information and displays voltages for every net in your
schematic; currents on pins are not visible, but are available for
display.
After this is done, it is up to you to decide where you want to
show currents and voltages. Schematics handles each separately
so that you can:
• show or hide voltages on selected wire segments
• show or hide currents on selected device pins
• turn off all of the displayed voltages, and then redisplay the
same voltages later
• turn off all of the displayed currents, and then redisplay the
same currents later
If
y
ou run more than one anal
y
sis t
y
pe
If you have set up more than one analysis, here are a few things
you should know about:
• Schematics always shows bias information for the analysis
that you last ran. PSpice A/D runs analyses in this order:
DC, AC, transient.
This means if you perform a multi-run analysis like
parametric, Monte Carlo, sensitivity/worst-case, or
temperature, you will see bias values for the last run only.
If
y
ou used IPROBE and
VIEWPOINT s
y
mbols in
earlier desi
g
ns...
...you don’t need to anymore. The
bias information is always available
and saves you steps.
When usin
g
symbols like IPROBE
and VIEWPOINT, you typically have
to:
1
Place IPROBE symbols to detect
the currents that you are
interested in. Each IPROBE
symbol introduces a new net into
the circuit.
2
Run one simulation and use
VIEWPOINT symbols to look at
bias point volta
g
es.
3
Connect IPROBE symbols to any
new device pins where you think
there may be problems.
4
Then run another simulation to
actually view the bias point
currents on problem devices.
Because you no lon
g
er need to place
these symbols to view bias
information, you can minimize the
number of simulations and symbols
that you need to debu
g
your circuit.
If
y
ou are usin
g
hierarchical
s
y
mbols or blocks...
Schematics automatically displays
pin currents for symbols representin
g
PSpice (.SUBCKT and .MODEL)
models, but not for hierarchical
symbols and blocks. If you want to
see currents on the pins of
hierarchical symbols, then you need
to use IPROBE symbols. To find out
more, see
If You Have Hierarchical
Symbols or Blocks on Your
Schematic on page 18-10.