Keithley S530 User Manual page 65

S530 Parametric Test System Test Subroutine Library User's Manual
re
This subroutine estimates emitter resistance (R
Usage
double re(int e, int b, int c, int sub, double ib1, double ib2, double vsub, int
npts, int *iflag, double *r)
e
b
c
sub
ib1
ib2
vsub
npts
iflag
r
Returns
Details
This subroutine uses Getreu's method (Ian Getreu, Modeling the Bipolar Transistor, Tektronix, 1976)
to estimate the emitter resistance modeling parameter. This routine should be used with caution
because the value returned may include some parasitic values. The technique sweeps base current
and measures the open (floating) developed collector voltage.
The subroutine assumes the device is in saturation. For a device in saturation, with the collector
open, Getreu gives:
V =kT/qln (1/
CE
Where:


= Reverse emitter efficiency
R

kT/q = 25.96 mV at 300 K

I = The base current
B

R = The emitter current
E

V = The collector-emitter voltage
CE
Plotting I
To calculate R
(LLSQ) line is fit to the extracted data. The emitter resistance is then the inverse of the calculated
slope. The result is returned in ohms.
S530-907-01 Rev. A / September 2015
Input The emitter pin of the device
Input The base pin of the device
Input The collector pin of the device
Input The substrate pin of the device
Input
The start of the base-emitter current (I
Input
The end of the I
Input Substrate bias, in volts
Input The number of points in the sweep
Output The status flag:




Output The correlation coefficient
Output The estimated emitter resistance
)+I R
R B E
versus V gives the slope as R
BE CE
, the V -I data is analyzed for positive slope data, and a linear least-squares
E CE BE
).
E
sweep, in amperes
BE
0 = Normal completion
1 = Insufficient points for LLSQ analysis
2 = Calculated LLSQ slope is 0.0
3 = Bad range specified in the call to the logstp subroutine
. The sample plot shows the typical V
E
Section 3: Test subroutine library reference
) sweep, in amperes
BE
-I characteristic.
CE BE
3-53