NPN - Gummel Plot and Ic/Vce Characterization

bjtex04.in : NPN - Gummel Plot and Ic/Vce Characterization

Requires: S-Pisces
Minimum Versions: Atlas 5.28.1.R

This example simulates a Gummel plot and the Ic vs. Vce characteristics for different values of base current of a silicon BJT. It shows:

  • Formation of an NPN BJT using Atlas syntax
  • Ic and Ib extraction versus Vbe (Gummel plot)
  • Ic extraction versus Vce for various Ib

The initial stage of the example uses the mesh, region, and electrode statements in Atlas to construct the NPN structure. Analytical doping profiles are added in the doping statement. The structure has a heavy n+ emitter, 1.0e18 peak base concentration, a buried collector layer and heavy p+ extrinsic base contact.

The contact statement is used to define the emitter contact as a N-type polysilicon emitter. Surface recombination is also specified at the polysilicon/ silicon interface. Next, the material statement is used to specify the electron and hole SRH lifetimes. The models bipolar statement is set to specify that the default set of bipolar models is to be used. The default set of bipolar models includes: concentration dependent mobility, field dependent mobility, band-gap narrowing, concentration dependent lifetimes and Auger recombination.

The gummel plot syntax is similar to that described in the first example of this section. The syntax for the Ic/Vce simulation is described under the PNP example in this section. The key point is the use of current boundary conditions on the base contact as defined by contact name=base current . This allows a constant base current to be forced while Vce is ramped. The family of Ic/Vce curves can be overlaid in TonyPlot or exported to UTMOST for SPICE model extraction.

To load and run this example, select the Load button in DeckBuild > Examples. This will copy the input file and any support files to your current working directory. Select the Run button in DeckBuild to execute the example.