L8002

Preliminary

CMOS IC

UNISONIC TECHNOLOGIES CO., LTD

5 of 6

www.unisonic.com.tw



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

There are three major functions provided by UTC L8002: support negative voltage, bias control circuit, and FET

protesting circuit.

The UTC L8002 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 -2V 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 L8002 in

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

the application circuits.