eldo_user

Setting Up An Analysis
Differences Between DC and OP Analyses
DC Convergence Troubleshooting
Differences Between DC and OP Analyses
The .DC and .OP commands (without any parameters specified) both determine the quiescent
state or DC Operating Point (DCOP) of the circuit. The operating point of the circuit is
computed with capacitances opened and inductances short-circuited.
Tip
See “.DC” and “.OP” in the Eldo Reference Manual.
The main difference between the commands is the information output to the .chi file:
• The .DC command only prints DC Operating Point information related to the node
voltages, source currents, and power dissipation. Look for the DC OPERATING POINT
section in the .chi file.
• The .OP command prints DC Operating Point information related to the node voltages,
source currents, and power dissipation, as well as the Operating Point table information
related to device bias. Look for the DC OPERATING POINT and OPERATING POINT
INFORMATION sections in the .chi file. The items in the OP table can also be
extracted, plotted, and printed.
When sweeping parameters (for example .STEP), with a .DC or .OP command specified with
no other analysis, a continuous waveform is generated when DC plots are requested. When
another analysis (for example .AC) is requested during a sweep together with .DC, Eldo
generates a single point waveform for each run and EZwave displays them as a compound
waveform. If a .OP command is specified instead of the .DC command, no DC plots are
generated.
Eldo automatically determines the DC Operating Point before performing the following
analyses:
• .AC without UIC parameter specified—a .OP is first performed, the SMALL SIGNAL
BIAS SOLUTION and OPERATING POINT INFORMATION are output to the .chi
file.
• .TRAN without UIC parameter specified—a .DC is first performed, no operating point
information is output to the .chi file.
• .DC sweep specified—a .DC is performed at each point of the DC sweep, no operating
point information is output to the .chi file.
Note
The SMALL SIGNAL BIAS SOLUTION is equivalent to the DC OPERATING
POINT information in the .chi file, just the label is different.
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Eldo® User's Manual, 15.3