11

Driving Cables and Capacitive Loads

When used as a cable driver, double termination is always

recommended for reflection-free performance. For those

applications, the back-termination series resistor will

decouple the EL2170, EL2270, and EL2470 from the cable

and allow extensive capacitive drive. However, other

applications may have high capacitive loads without a back-

termination resistor. In these applications, a small series

resistor (usually between 5

Ω and 50Ω) can be placed in

series with the output to eliminate most peaking. The gain

loss which may be created by this additional resistor at the

output. In many cases it is also possible to simply increase

peaking.

Current Limiting

The EL2170, EL2270, and EL2470 have no internal current-

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 device.

Power Dissipation

With the high output drive capability of the EL2170, EL2270,

and EL2470, it is possible to exceed the 150°C Absolute

Maximum junction temperature under certain very high load

about 25

Ω, it is important to calculate the maximum junction

power-supply voltages, load conditions, or package type

need to be modified for the EL2170, EL2270, and EL2470 to

remain in the safe operating area. These parameters are

calculated as follows [1]:

where:

n = Number of amplifiers in the package

the package

where:

Typical Application Circuits

T

JMAX

T

MAX

Θ

JA

nPD

MAX

×

×

()

+

=

PD

MAX

2

(

V

S

I

V

S

(

- V

V

OUTMAX

R

L

----------------------------

×

+

×

×

=

INVERTING 200mA OUTPUT CURRENT

DISTRIBUTION AMPLIFIER

FAST-SETTLING PRECISION AMPLIFIER

EL2170, EL2270, EL2470