10

FN7307.6

October 30, 2006

The gain setting for EL5371 is:

Where:

FIGURE 24.

Choice of Feedback Resistor and Gain Bandwidth

Product

For applications that require a gain of +1, no feedback

resistor is required. Just short the OUT+ pin to FBP pin and

OUT- pin to FBN pin. For gains greater than +1, the

feedback resistor forms a pole with the parasitic capacitance

at the inverting input. As this pole becomes smaller, the

amplifier's phase margin is reduced. This causes ringing in

the time domain and peaking in the frequency domain.

must be used, a small capacitor in the few Pico farad range

peaking at the expense of reducing the bandwidth.

The bandwidth of the EL5171 and EL5371 depends on the

with the load for gains other than +1. As this combination gets

minimum value that should not be exceeded for optimum

For the gains other than +1, optimum response is obtained

The EL5171 and EL5371 have a gain bandwidth product of

predicted by the following equation:

Driving Capacitive Loads and Cables

The EL5171 and EL5371 can drive 50pF differential

capacitor in parallel with 1k

Ω differential load with less than

5dB of peaking at gain of +1. If less peaking is desired in

applications, a small series resistor (usually between 5

Ω to

50

Ω) can be placed in series with each output to eliminate

most peaking. However, this will reduce the gain slightly. If

then be chosen to make up for any gain loss which may be

created by the additional series resistor at the output.

When used as a cable driver, double termination is always

recommended for reflection-free performance. For those

applications, a back-termination series resistor at the

amplifier's output will isolate the amplifier from the cable and

allow extensive capacitive drive. However, other applications

may have high capacitive loads without a back-termination

resistor. Again, a small series resistor at the output can help

to reduce peaking.

Disable/Power-Down (for EL5371 only)

The EL5371 can be disabled and placed its outputs in a high

impedance state. The turn off time is about 0.95µs and the

turn on time is about 215ns. When disabled, the amplifier's

typically, thereby effectively eliminating the power

consumption. The amplifier's power down can be controlled

by standard CMOS signal levels at the ENABLE pin. The

enable the amplifier. The amplifier will be disabled when the

Output Drive Capability

The EL5171 and EL5371 have internal short circuit

protection. Its typical short circuit current is ±90mA for

EL5171 and ±70mA for EL5371. If the output is shorted

indefinitely, the power dissipation could easily increase such

that the part will be destroyed. Maximum reliability is

maintained if the output current never exceeds ±60mA. This

limit is set by the design of the internal metal

interconnections.

Power Dissipation

With the high output drive capability of the EL5171 and

EL5371. It is possible to exceed the 135°C absolute maximum

junction temperature under certain load current conditions.

Therefore, it is important to calculate the maximum junction

temperature for the application to determine if the load

conditions or package types need to be modified for the

amplifier to remain in the safe operating area.

The maximum power dissipation allowed in a package is

determined according to:

(

+

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

+

⎝⎠

⎜⎟

⎛⎞

×

–

=

(

-----------

+

⎝⎠

⎜⎟

⎛⎞

×

–

=

=

FBP

IN+

IN-

REF

FBN

Gain BW

100MHz

=

×

–

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

=

EL5171, EL5371