ZNBR4000 ZNBR4001
ZNBR6000 ZNBR6001
FET BIAS CONTROLLER
DRAFT ISSUE A - DECEMBER 2000
DEVICE DESCRIPTION
These devices are unconditionally stable
over the full working temperature with the
FETs in place, subject to the inclusion of the
recommended gate and drain capacitors.
These ensure RF stability and minimal
injected noise.
The ZNBR series of devices are designed to
meet the bias requirements of GaAs and
HEMT FETs commonly used in satellite
receiver LNBs, PMR, cellular telephones etc.
with a minimum of external components
and a VCC of 3-6V for improved efficiency.
It is possible to use less than the devices full
complement of FET bias controls, unused
drain and gate connections can be left open
circuit without affecting operation of the
remaining bias circuits.
With the addition of two capacitors and
resistors the devices provide drain voltage
and current control for a number of external
grounded source FETs, generating the
regulated negative rail required for FET gate
biasing whilst operating from a single
supply. This negative bias, at -3 volts, can
also be used to supply other external
circuits.
In order to protect the external FETs the
circuits have been designed to ensure that,
under any conditions including power
up/down transients, the gate drive from the
bias circuits cannot exceed the range -2.5V
to 0.7V. Furthermore if the negative rail
experiences a fault condition, such as
overload or short circuit, the drain supply to
the FETs will shut down avoiding excessive
current flow.
The ZNBR4000/1 and ZNBR6000/1 contain
four and six bias stages respectively. In
setting drain current the ZNBR4000/1 two
resistors allows individual FET pair control
to different levels, the ZNBR6000/1 two
resistors split control between two and four
FETs. This allows the operating current of
input FETs to be adjusted to minimise noise,
whilst the following FET stages can
separately be adjusted for maximum gain.
The series also offers the choice of drain
voltage to be set for the FETs, the
ZNBR4000/6000 gives 2.2 volts drain whilst
the ZNBR4001/6001 gives 2 volts.
The ZNBR4000/1 and ZNBR6000/1 are
available in QSOP16 and 20 pin packages
respectively fortheminimumin devicessize.
Device operating temperature is -40 to 70°C
to suit a wide range of environmental
conditions.
FEATURES
APPLICATIONS
VCC of 3-6V for improved efficiency
Satellite receiver LNBs
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•
Provides bias for GaAs and HEMT FETs
Private mobile radio (PMR)
•
•
Drives up to four or six FETs
Cellular telephones
•
•
Dynamic FET protection
•
Drain current set by external resistor
•
Regulated negative rail generator
requires only 2 external capacitors
•
Choice in drain voltage
•
Wide supply voltage range
•
QSOP surface mount package
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