Silicon Discrete Components
Application Considerations
for the Integrated Bias Control Circuits
BCR400R and BCR400W
Figure 1
Application Note No. 014
RF Transistor Controlled by BCR400
Operating Point
• BCR400 stabilizes the operating current (i.e. IC or ID), the collector (or drain) voltage
depends on the supply voltage: VCE = VS - 0.65 V
• The voltage drop of approximately 0.65 V on Rext (i.e. between pins 3 and 4 of
BCR400) is almost constant (Rext = 0.65 V x IC)
• In case a lower VCE is really required (e.g. to prevent exceeding of maximum VCE or
VDS ratings), an additional resistor R = (VS - VCE - 0.65 V) / IC can be inserted either
between pin 4 and collector (or drain) or in series to the supply voltage VS, thus
providing an additional voltage drop.
Application Note
Application Considerations for the Integrated
Bias Control Circuits BCR400R and BCR400W
BCR400 stabilizes bias current of transistors in an active control loop. In order to avoid
loop oscillation (hunting), time constants must be chosen adequately, i.e. C1 >= 10 x C2.
It is strongly recommended that the entire DC circuit is analyzed and optimized for
stability with one of the commercially available SPICE simulators.
Thermal considerations
The collector or drain current of a stabilized RF transistor does not directly affect
BCR400, as it must only provide the base current (or gate bias current). Even as a standalone current source it is not possible to exceed Ptot (up to Ts = 115°C), if the maximum
ratings of Vs and Icontr are adhered to (see data sheet).
Preliminary SPICE Parameters
IS= 6.00E-15
N= 1.20E+00
RS= 5.0E+01
IBV= 1.00E-04 BV= 7.50E+01
M= 1.00E-01
CJO= 6.87E-13 EG= 1.11E+00
TT= 8.66E-09
VJ= 2.00E+00
XTI= 5.00E+00)
* one internal Diode of BCR400
BF= 3.00E+02
BR= 3.38E+00
CJC= 2.00E-12
CJE= 1.56E-11
CJS= 0.00E+00
EG= 1.11E+00
FC= 8.28E-01
IKF= 1.00E-02
IKR= 0.40E-02
IRB= 0.30E-06
IS= 0.30E-14
ISC= 2.00E-14
ISE= 0.50E-13
ITF= 0.50E-01
MJC= 3.49E-01
MJE= 4.18E-01
MJS= 3.30E-01
NC= 1.19E+00
NE= 1.83E+00
NF= 1.00E+00
NR= 1.00E+00
PTF= 0.00E+00
RB= 1.00E+02
RBM= 1.00E+01
RC= 5.00E+00
RE= 2.00E-01
TF= 6.05E-10
TR= 0.00E+00
VAF= 5.90E+01
VAR= 1.74E+01
VJC= 3.00E-01
VJE= 8.00E-01
VJS= 7.50E-01
VTF= 4.39E+00
XCJC= 1.00E+00
XTB= 0.00E+00
XTF= 5.81E+00
XTI= 1.50E+00)
* internal parallel resistance Rint= 6.5 kOhm
* Rb= 75 kOhm
Application Note
Application Considerations for the Integrated
Bias Control Circuits BCR400R and BCR400W
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Edition 2000-07-27
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