ZNBG3000 Просмотр технического описания (PDF) - Zetex => Diodes

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ZNBG3000

FET BIAS CONTROLLER

Zetex => Diodes 

ZNBG3000

ZNBG3001

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 CD and CG ensure that residual power supply and substrate generator noise is not

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 CNB and CSUB are an integral part of the ZNBGs negative supply generator. The

negative bias voltage is generated on-chip using an internal oscillator. The required value of

capacitors CNB and CSUB is 47nF. This generator produces a low current supply of approximately

-3 volts. Although this generator is intended purely to bias the external FETs, it can be used to

power other external circuits via the CSUB pin.

Resistor RCAL1 sets the drain current at which all external FETs are operated. If any bias control

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 RCAL should still be included. The supply current can be

reduced, if required, by using a high value RCAL resistor (e.g. 470k).

4-142

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