# 8. Solver

## 8.1. Solver

`DEVSIM` uses Newton methods to solve the system of PDE’s. All of the analyses are performed using the `devsim.solve()`.

## 8.2. DC analysis

A DC analysis is performed using the `devsim.solve()`.

```solve(type="dc", absolute_error=1.0e10, relative_error=1e-7 maximum_iterations=30)
```

## 8.3. AC analysis

An AC analysis is performed using the `devsim.solve()`. A circuit voltage source is required to set the AC source.

## 8.4. Noise/Sensitivity analysis

An noise analysis is performed using the `devsim.solve()` command. A circuit node is specified in order to find its sensitivity to changes in the bulk quantities of each device. If the circuit node is named `V1.I`. A noise simulation is performed using:

```solve(type="noise", frequency=1e5, output_node="V1.I")
```

Noise and sensitivity analysis is performed using the `devsim.solve()`. If the equation begin solved is `PotentialEquation`, the names of the scalar impedance field is then:

• `V1.I_PotentialEquation_real`

• `V1.I_PotentialEquation_imag`

and the vector impedance fields evaluated on the nodes are

• `V1.I_PotentialEquation_real_gradx`

• `V1.I_PotentialEquation_imag_gradx`

• `V1.I_PotentialEquation_real_grady` (2D and 3D)

• `V1.I_PotentialEquation_imag_grady` (2D and 3D)

• `V1.I_PotentialEquation_real_gradz` (3D only)

• `V1.I_PotentialEquation_imag_gradz` (3D only)

## 8.5. Transient analysis

Transient analysis is performed using the `devsim.solve()`. `DEVSIM` supports time-integration of the device PDE’s. The three methods are supported are:

• BDF1

• TRBDF

• BDF2