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6.1.1 DC Analysis

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.