EL2276CS datasheet(12/20 Pages) ELANTEC

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EL2176CEL2276C

70 MHz1 mA Current Mode Feedback Amp wDisable

Applications Information

Contd

entire 1 mA supply current of each EL2176C

EL2276C amplifier Special circuitry has been in-

corporated in the EL2176CEL2276C to reduce

the variation of output impedance with current

output This results in dG and dP specifications

of 015% and 015 while driving 150

X at a gain

of a2

Video Performance has also been measured with

a 500

X load at a gain of a1 Under these condi-

tions the EL2176CEL2276C have dG and dP

specifications of 001% and 002

respectively

while driving 500

X at AV ea1

Output Drive Capability

In spite of its low 1 mA of supply current the

EL2176C is capable of providing a minimum of

80 mA of output current Similarly each am-

plifier of the EL2276C is capable of providing a

minimum of g50 mA These output drive levels

are unprecedented in amplifiers running at these

supply currents With a minimum g80 mA of

output drive the EL2176C is capable of driving

X loads to g4V making it an excellent choice

for driving isolation transformers in telecommu-

nications applications Similarly the g50 mA

minimum output drive of each EL2276C amplifi-

er allows swings of g25V into 50

X loads

Driving Cables and Capacitive Loads

When used as a cable driver double termination

is always recommended for reflection-free per-

formance For those applications the back-termi-

nation series resistor will decouple the EL2176C

EL2276C from the cable and allow extensive ca-

pacitive drive However other applications may

have high capacitive loads without a back-termi-

nation resistor In these applications a small se-

ries resistor (usually between 5

X and 50X) can be

placed in series with the output to eliminate most

peaking The gain resistor (RG) can then be cho-

sen to make up for any gain loss which may be

created by this additional resistor at the output

In many cases it is also possible to simply in-

crease the value of the feedback resistor (RF)to

reduce the peaking

Current Limiting

The EL2176CEL2276C have no internal cur-

rent-limiting circuitry If any output is shorted

it is possible to exceed the Absolute Maximum

Ratings for output current or power dissipation

potentially resulting in the destruction of the de-

vice

Power Dissipation

With the high output drive capability of the

EL2176CEL2276C it is possible to exceed the

150 C Absolute Maximum junction temperature

under certain very high load current conditions

Generally speaking when RL falls below about

X it is important to calculate the maximum

junction temperatu re (TJmax) for the application

to determine if power-supply voltages load con-

ditions or package type need to be modified for

the EL2176CEL2276C to remain in the safe op-

erating area These parameters are calculated as

follows

TJMAX e TMAX a (iJA n PDMAX)

where

TMAX

Maximum Ambient Temperature

iJA

Thermal Resistance of the Package

Number of Amplifiers in the Pack-

age

PDMAX e Maximum Power Dissipation of

Each Amplifier in the Package

PDMAX for each amplifier can be calculated as

follows

PDMAX e (2 VS ISMAX) a

(VS b VOUTMAX) (VOUTMAX RL))

where

Supply Voltage

ISMAX

Maximum Supply Current of 1

Amplifier

VOUTMAX e Max Output Voltage of the Ap-

plication

Load Resistance

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