ZNBG3000 データシートの表示（PDF） - Diodes Incorporated.

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ZNBG3000

FET BIAS CONTROLLER

Diodes Incorporated. 

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.

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