L8001

Preliminary

CMOS IC

UNISONIC TECHNOLOGIES CO., LTD

5 of 6

www.unisonic.com.tw

QW-R502-938.d



T Y PI CAL APPLI CAT I ON CI RCU I T

There are three major functions provided by L8001G: support negative voltage, bias control circuit, and FET

protesting circuit.

The bias control circuit is used to establish a stable bias current for FETs.

It’s bias current can be adjusted by

L8001G. if the same drain current is required for all FETs then pins Ical1 and Ical2 can be wired together and

shunted to ground by a single resistor of half normal value.

The L8001G devices have been designed to protect the external FETs from adverse operating conditions. With a

JFET connected to any bias circuit, the gate output voltage of the bias circuit can not exceed the range -2.5V to 0.7V,

under any conditions including powerup and powerdown transients. Should the negative bias generator be shorted

or overloaded so that the drain current of the external FETs can no longer be controlled, the drain supply to FETs is

shut down to avoid damage to the FETs by excessive drain current. The following diagrams show the L8001G in

typical LNB applications. Within each FET gain stage the numbering system indicates how the bias stages relate to

the application circuits. This is important when RCAL values are used to set differing drain currents.