# 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