Application Considerations for the Integrated

Bias Control Circuits BCR400R and BCR400W

Application Note

2

2000-07-27

Stability

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.

C

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 stand-

alone current source it is not possible to exceed

P

ratings of

V

Preliminary SPICE Parameters

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.MODEL DI400 D(

+

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

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.MODEL TR400 PNP(

+

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)

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* internal parallel resistance Rint= 6.5 kOhm

* Rb= 75 kOhm

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