13

EL5293C

Dual 300MHz Current Feedback Amplifier

stability increases. Since the loop stability is improving

with higher closed-loop gains, it becomes possible to

still retain stability, resulting in only a slight loss of

bandwidth with increased closed-loop gain.

Supply Voltage Range and Single-Supply

Operation

The EL5293C has been designed to operate with supply

voltages having a span of greater than 5V and less than

10V. In practical terms, this means that the EL5293C

will operate on dual supplies ranging from ±2.5V to

±5V. With single-supply, the EL5293C will operate

from 5V to 10V.

As supply voltages continue to decrease, it becomes nec-

essary to provide input and output voltage ranges that

can get as close as possible to the supply voltages. The

EL5293C has an input range which extends to within 2V

of either supply. So, for example, on +5V supplies, the

EL5293C has an input range which spans ±3V. The out-

put range of the EL5293C is also quite large, extending

to within 1V of the supply rail. On a ±5V supply, the

+4V. Single-supply output range is larger because of the

increased negative swing due to the external pull-down

resistor to ground.

Video Performance

For good video performance, an amplifier is required to

maintain the same output impedance and the same fre-

quency response as DC levels are changed at the output.

This is especially difficult when driving a standard video

load of 150

Ω, because of the change in output current

with DC level. Previously, good differential gain could

only be achieved by running high idle currents through

the output transistors (to reduce variations in output

impedance.) These currents were typically comparable

to the entire 4mA supply current of each EL5293C

amplifier. Special circuitry has been incorporated in the

EL5293C to reduce the variation of output impedance

with current output. This results in dG and dP specifica-

tions of 0.03% and 0.04°, while driving 150

Ω at a gain

of 2.

Video performance has also been measured with a 500

Ω

load at a gain of +1. Under these conditions, the

EL5293C has dG and dP specifications of 0.03% and

0.04°.

Output Drive Capability

In spite of its low 4mA of supply current, the EL5293C

is capable of providing a minimum of ±95mA of output

current. With a minimum of ±95mA of output drive, the

EL5293C is capable of driving 50

Ω loads to both rails,

making it an excellent choice for driving isolation trans-

formers in telecommunications applications.

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 resis-

tor will decouple the EL5293C from the cable and allow

extensive capacitive drive. However, other applications

may have high capacitive loads without a back-termina-

tion 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

the peaking.

Current Limiting

The EL5293C has no internal current-limiting circuitry.

If the output is shorted, it is possible to exceed the Abso-

lute Maximum Rating for output current or power

dissipation, potentially resulting in the destruction of the

device.

Power Dissipation

With the high output drive capability of the EL5293C, it

is possible to exceed the 125°C Absolute Maximum

junction temperature under certain very high load cur-

about 25

Ω, it is important to calculate the maximum

determine if power supply voltages, load conditions, or

package type need to be modified for the EL5293C to