znbg3000 Zetex Semiconductors plc., znbg3000 Datasheet - Page 6

• Manufacturer Part Number: znbg3000
• Description: Fet Bias Controller
• Manufacturer: Zetex Semiconductors plc.

TYPICAL APPLICATION CIRCUIT
APPLICATIONS INFORMATION
The above is a partial application circuit for the ZNBG series showing all external components
required for appropriate biasing. The bias circuits are unconditionally stable over the full
temperature range with the associated FETs and gate and drain capacitors in circuit.
Capacitors C
allowed to affect other external circuits which may be sensitive to RF interference. They also
serve to suppress any potential RF feedthrough between stages via the ZNBG device. These
capacitors are required for all stages used. Values of 10nF and 4.7nF respectively are
recommended however this is design dependent and any value between 1nF and 100nF could
be used.
The capacitors C
negative bias voltage is generated on-chip using an internal oscillator. The required value of
capacitors C
-3 volts. Although this generator is intended purely to bias the external FETs, it can be used to
power other external circuits via the C
Resistor R
circuit is not required, its related drain and gate connections may be left open circuit without
affecting the operation of the remaining bias circuits. If all FETs associated with a current setting
resistor are omitted, the particular R
reduced, if required, by using a high value R
ZNBG3000
ZNBG3001
CAL1
NB
D
and C
sets the drain current at which all external FETs are operated. If any bias control
and C
NB
and C
G
SUB
ensure that residual power supply and substrate generator noise is not
is 47nF. This generator produces a low current supply of approximately
SUB
are an integral part of the ZNBGs negative supply generator. The
CAL
SUB
should still be included. The supply current can be
pin.
CAL
4-142
resistor (e.g. 470k).