L8200

LINEAR INTEGRATED CIRCUIT

UNISONIC TECHNOLOGIES CO., LTD

5 of 6

www.unisonic.com.tw

QW-R123-017.G



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

UTC L8200

G1

D1

D2

G2

HB

LB

CSUB

JF1

C*

L*

C1

10nF

L*

C*

C2

10nF

* Stripline Elements

22k

Ω

22k

Ω

47nF

To other FET stages

Power supply for IF Amps

RL1

RH1

RL2

QL

CL1

RH2

9.75GHz Local Osc.

10.6GHz Local Osc.

QH

CH1

LNB power and tone signal

Capacitors C1 and C2 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 feed

through between stages via the UTC L8200. 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 capacitor CSUB is an integral part of the UTC L8200 ’s negative supply generator. The negative

bias voltage is generated on-chip using an internal oscillator. The required value of capacitor CSUB is 47nF. This

generator produces a low current supply of approximately -3V. Although this generator is intended purely to bias the

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. The UTC L8200 have been designed to protect the external FETs form

adverse operating conditions. With a JFET connected to any bias circuit, the gate output voltage of the bias circuit

can not exceed the range -3.0V~1V under any conditions, including power up and power down 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. UTC

L8200

incorporates over and under voltage protection so is the receiver or installation develops a fault the LNB will

shut down and restart once operating conditions are back to normal.