The dc analysis portion of NGSPICE determines the dc operating point of
the circuit with inductors shorted and capacitors opened. The dc
analysis options are specified on the .DC
, .TF
, and .OP
control lines.A dc analysis is automatically performed prior to a transient
analysis to determine the transient initial conditions, and prior to an ac
small-signal analysis to determine the linearized, small-signal models
for nonlinear devices. If requested, the dc small-signal value of a
transfer function (ratio of output variable to input source), input
resistance, and output resistance is also computed as a part of the dc
solution. The dc analysis can also be used to generate dc transfer
curves: a specified independent voltage, current source, resistor or
temperature is stepped over a user-specified range and the dc output
variables are stored for each sequential source value.
Temperature (TEMP
) and resistance sweeps have been introduced
in NGSPICE, they were not available in the original code of Spice3f5.