The DC analysis portion of DR. SPICE determines the DC operating point of the circuit with inductors shorted and capacitors opened. 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 non-linear devices. The DC analysis can also be used to generate DC transfer curves: a specified independent voltage or current source is stepped over a user-specified range and the DC output variables are stored for each sequential source value.
This is one of the example circuits provided with DR. SPICE. You can run the simulation and view the results.
The circuit schematic looks like this:
CKT1.CIR Circuit Schematic
The SPICE file created from the schematic is available in the examples directory as ckt1.cir. The file looks like this:
SIMPLE CLASS B OUTPUT STAGE VIN IN 0 SIN(0 5 10K) VCC VCC 0 12V VEE VEE 0 -12V Q1 VCC IN OUT MODN Q2 VEE IN OUT MODP RLOAD OUT 0 10K .OP .MODEL MODN NPN .MODEL MODP PNP .TRAN 1U 100U .END
If you open the SPICE file and run it now, the output from the Simulation Menu=>OP should look like:
Resulting Branch Currents and Node Voltages