S530 Parametric Test System Test Subroutine Library User's Manual
Section 3: Test subroutine library reference
S530-907-01 Rev. A / September 2015
3-53
re
This subroutine estimates emitter resistance (R
E
).
Usage
double re(int
e
, int
b
, int
c
, int
sub
, double
ib1
, double
ib2
, double
vsub
, int
npts
, int
*iflag
, double
*r
)
e
Input
The emitter pin of the device
b
Input
The base pin of the device
c
Input
The collector pin of the device
sub
Input
The substrate pin of the device
ib1
Input
The start of the base-emitter current (I
BE
) sweep, in amperes
ib2
Input
The end of the I
BE
sweep, in amperes
vsub
Input
Substrate bias, in volts
npts
Input
The number of points in the sweep
iflag
Output
The status flag:
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
r
Output
The correlation coefficient
Returns
Output
The estimated emitter resistance
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
CE
=kT/qln (1/
R
)+I
B
R
E
Where:
R
= Reverse emitter efficiency
kT/q = 25.96 mV at 300 K
I
B
= The base current
R
E
= The emitter current
V
CE
= The collector-emitter voltage
Plotting I
BE
versus V
CE
gives the slope as R
E
. The sample plot shows the typical V
CE
-I
BE
characteristic.
To calculate R
E
, the V
CE
-I
BE
data is analyzed for positive slope data, and a linear least-squares
(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.
