A Product Line of
The ZNBG series of devices are designed to meet the bias
requirements of GaAs and HEMT FETs commonly used in
satellite receiver LNBs with a minimum of external
The ZNBG4003 provides four FET bias stages, arranged in
two pairs of two. Resistors connected to pins Rcal1 and
Rcal2 set the FET drain currents of each pair over the range
of 0 to 15mA, allowing input FETs to be biased for optimum
noise and amplifier FETs for optimum gain.
Drain voltages of all stages are set at 2.0V. The drain
supplies are current limited to approximately 5% above the
operating currents set by the Rcal resistors.
Depletion mode FETs require a negative voltage bias supply
when operated in grounded source circuits. The ZNBG4003
includes an integrated switched capacitor DC-DC converter
generating a regulated output of -2.5V to allow single supply
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.
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
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
-3V. Additionally each stage has its own individual current
limiter. 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.
To minimise PCB space ZNBG4003 is packaged in the
16 pin 3mm x 3mm QFN package.
Device operating temperature is -40°C to 85°C to suit a wide
range of environmental conditions.
Document number: DS35007 Rev. 1 - 2
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