Section 3: Test subroutine library reference
S530 Parametric Test System Test Subroutine Library User's Manual
3-50
S530-907-01 Rev. A / September 2015
rcsat
This subroutine estimates the collector resistance (R
C
) modeling parameter when collector current (I
C
) and base
current (I
B
) are swept at a constant beta (
).
Usage
double rcsat(int
e
, int
b
, int
c
, int
sub
, double
ice1
, double
ice2
, double
beta
,
double
vsub
, int
npts
, double
*r
, int
*iflag
)
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
ice1
Input
The start of the collector-emitter current (I
CE
) sweep, in amperes
ice2
Input
The end of the I
CE
sweep, in amperes
beta
Input
The current ratio, I
C
/I
B
vsub
Input
The forced substrate bias, in volts
npts
Input
The number of points in the sweep
r
Output
The correlation coefficient
iflag
Output
The status flag:
0 = Normal completion
1 = Insufficient points for LLSQ analysis
2 = Calculated LLSQ slope is 0.0
Returns
Output
The collector resistance modeling parameter
Details
This subroutine estimates the modeling parameter RC in the saturation region of a transistor using
Getreu's method (Ian Getreu,
Modeling the Bipolar Transistor
, Tektronix, 1976). Current is stepped
into the base and collector at a specified
(normally 10). The developed collector-emitter voltage
(V
CE
) is measured. V
CE
and I
CE
data is extracted from the positive slope portion of the curve, and a
linear least-squares (LLSQ) line is fit to the data. The inverse of the slope of this line gives R
CSAT
. The
device is in the common-emitter configuration.
For high-speed or microwave bipolar devices, best results are obtained by starting at the maximum
current and sweeping the current to a lower value.
An incorrect value of
can result in a large excursion of V
CE
, which may break down the device.
Because of this, the collector voltage is limited to 16 V.
To measure R
C SAT
correctly, make sure the transistor is saturated. You can do this by entering a
smaller than actual value for
(overdriving the base).
