Using DC Simulation

This section describes when to use a DC simulation, how to set it up, and the basic simulation process used to collect data.

License Requirements

The DC simulation uses the Linear Simulator license (sim_linear). You must have this license to run DC simulations. You can work with examples described here and installed with the software without the license, but you will not be able to simulate them.

When to Use DC Simulation

A single-point DC simulation automatically precedes every AC, S-parameter, transient, harmonic balance, and circuit envelope simulation. This serves as the starting point for these simulations. For AC and S-parameter simulations, it determines linearized models for the nonlinear components. For transient, harmonic balance, and circuit envelope simulations, it determines an initial estimate used for nonlinear simulation.

A DC simulation also can be done manually in ADS by using the DC simulation controller. Start by creating your design, add any relevant current probes, then identify and name the nodes from which you want to collect data. The DC simulation setup then provides for both single-point and swept simulations. Swept variables can be related to voltage or current source values, or to other component parameter values. By performing a DC swept bias or swept variable simulation, you can check the operating point of the circuit against a swept parameter such as a bias supply voltage or a temperature.

Use DC simulation to:

• Verify the proper DC operating characteristics of the design under test.
• Determine the power consumption of your circuit.
• Verify model parameters by comparing the DC transfer characteristics (I-V curves) of the model with actual measurements.
• Display voltages and currents after a simulation.
• Provide data for DC back-annotation.

How to Use DC Simulation

The following guidelines will help you set up a DC simulation in ADS.

• Add the DC simulation component to the schematic. If you do not edit the default settings, values will be calculated for the current probes and nodes added to the circuit, based on the settings of the schematic's other components.
• To sweep a parameter over a range, such as varying an input voltage or changing a resistor value, double-click the simulation component and select the Sweep tab. Enter the name of the parameter to sweep. Select the sweep type and enter the range.
• If additional sweeps are needed, an external parameter sweep can be added.
• For details about each parameter, click Help from the open dialog box.

What Happens During DC Simulation

The DC simulation technique relies on an iterative process of mathematical convergence toward a solution. By manipulating a system of nonlinear ordinary differential equations, it solves for an equilibrium point in the nonlinear algebraic equations that describe a circuit based on a set of assumptions. For details, see Theory of Operation for DC Simulation.