Bipolar Transistor Characterization

This chapter describes the University of California at Berkeley bipolar transistor model supported in SPICE. Descriptions of model setup, instrument connections, and model parameters are included. Information is included for making DC, capacitance, and high-frequency AC measurements and their corresponding extractions.

The IC-CAP bipolar modeling module provides setups that can be used for general measurement and model extraction for bipolar devices. Two example files are provided for the bipolar model; the example files can also be used as a template for creating custom model configurations.

bjt_npn.mdl extracts parameters for NPN bipolar transistors

bjt_pnp.mdl extracts parameters for PNP bipolar transistors

The IC-CAP system offers the flexibility to modify any measurement or simulation specification.

The model extractions provided are also intended for general bipolar IC processes. If you have another method of extracting specific model parameters, you can do so with the Program function by writing a function in C and linking it to the function list. For Program function details or for writing user-defined C-language routines, refer to Chapter 9, "Using Transforms and Functions," in the IC-CAP User's Guide.

The following shows an example custom extraction for IS and NF:

 ! Extraction for IS & NF
! Note: print statements go to the
!       window that started IC-CAP
print "Example Custom Extraction for IS & NF"
index = 0             ! array index
! pick two low current points
v1 = -ve[index]
WHILE v1 < 0.4        ! get a point near Vbe = 0.4
  index = index + 1
  v1 = -ve[index]
END WHILE
i1 = ic.m[index]
v2 = -ve[index]
WHILE v2 < 0.5        ! get a point near Vbe = 0.5
  index = index + 1
  v2 = -ve[index]
END WHILE
i2 = ic.m[index]
! extract IS & NF
vt = 8.62e-5 * (TNOM + 273.15) ! thermal voltage
NF = 1 / vt * (v2 - v1) / log(i2 / i1)
IS = sqrt(i1 * i2) / exp((v1 + v2) / (2 * NF * vt))
print "IS = ";IS;"   NF = ";NF
print "... end of custom extraction ..."