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PDF ZNBG3001Q16 Data sheet ( Hoja de datos )
| Número de pieza | ZNBG3001Q16 | |
| Descripción | FET BIAS CONTROLLER | |
| Fabricantes | Zetex Semiconductors | |
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Hay una vista previa y un enlace de descarga de ZNBG3001Q16 (archivo pdf) en la parte inferior de esta página. Total 9 Páginas | ||
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FET BIAS CONTROLLER
ISSUE 1- AUGUST 1998
DEVICE DESCRIPTION
The ZNBG 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.
With the addition of two capacitors and a
resistor the devices provide drain voltage
and current control for 3 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.
The ZNBG3000/1 contains three bias stages.
A single resistor allows FET drain current to
be set to the desired level. The series also
offers the choice of drain voltage to be set
for the FETs, the ZNBG3000 gives 2.2 volts
drain whilst the ZNBG3001 gives 2 volts.
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.
FEATURES
• Provides bias for GaAs and HEMT FETs
• Drives up to three FETs
• 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
ZNBG3000
ZNBG3001
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.
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 -3.5V
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 ZNBG3000/1 are available in QSOP16
packages for the minimum in devices size.
Device operating temperature is -40 to 70°C
to suit a wide range of environmental
conditions.
APPLICATIONS
• Satellite receiver LNBs
• Private mobile radio (PMR)
• Cellular telephones
• Single in single out C Band LNB
4-137
1 page  
FUNCTIONAL DIAGRAM
ZNBG3000
ZNBG3001
FUNCTIONAL DESCRIPTION
The ZNBG devices provide all the bias requirements for external FETs, including the generation
of the negative supply required for gate biasing, from the single supply voltage.
The diagram above shows a single stage from the ZNBG series. The ZNBG3000/1 contains 3 such
stages.
The drain voltage of the external FET QN is set by the ZNBG device to its normal operating voltage.
This is determined by the on board VD Set reference, for the ZNBG3000 this is nominally 2.2 volts
whilst the ZNBG3001 provides nominally 2 volts.
The drain current taken by the FET is monitored by the low value resistor ID Sense. The amplifier
driving the gate of the FET adjusts the gate voltage of QN so that the drain current taken matches
the current called for by an external resistor RCAL. Both ZNBG devices have the facility to program
different drain currents into selected FETs.
Since the FET is a depletion mode transistor, it is usually necessary to drive its gate negative with
respect to ground to obtain the required drain current. To provide this capability powered from
a single positive supply, the device includes a low current negative supply generator. This
generator uses an internal oscillator and two external capacitors, CNB and CSUB.
4-141
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| PDF Descargar | [ Datasheet ZNBG3001Q16.PDF ] | |
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