5. Parameters

Parameters can be set using the commands in Material Commands. There are two complementary formalisms for doing this.

5.1. Parameters

Parameters are set globally, on devices, or on regions of a device. The models on each device region are automatically updated whenever parameters change.

devsim.set_parameter(device="device", region="region",
  name="ThermalVoltage", value=0.0259)

They may also be used to control program behavior, as listed in Table 5.1:

Table 5.1 Parameters controlling program behavior.

Parameter	Description
debug_level	info, verbose Section 9.3.5
threads_available	value=1, Section 9.3.6
threads_task_size	value=?, Section 9.3.6
node_volume_model	Section 4.6
edge_couple_model	Section 4.6
edge_node0_volume_model	Section 4.6
edge_node1_volume_model	Section 4.6
element_edge_couple_model	Section 4.6
element_node0_volume_model	Section 4.6
element_node1_volume_model	Section 4.6
extended_solver	value=False Extended precision matrix and RHS assembly and error evaluations. Linear solver and circuit assembly is still double precision``
extended_model	value=False Extended precision model evaluation
extended_equation	value=False Extended precision equation evaluation

5.2. Material database entries

Alternatively, parameters may be set based on material types. A database file is used for getting values on the regions of the device.

devsim.create_db(filename="foodb")
devsim.add_db_entry(material="global", parameter="q", value=1.60217646e-19,
  unit="coul", description="Electron Charge")
devsim.add_db_entry(material="Si", parameter="one",
  value=1, unit="", description="")
devsim.close_db

When a database entry is not available for a specific material, the parameter will be looked up on the global material entry.

5.3. Discussion

Both parameters and material database entries may be used in model expressions. Parameters have precedence in this situation. If a parameter is not found, then DEVSIM will also look for a circuit node by the name used in the model expression.