EL5174, EL5374

FN7313 Rev 9.00

Page 11 of 15

August 12, 2015

FIGURE 26.

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

maximum value that should not be exceeded for optimum

help to reduce the ringing and peaking at the expense of

reducing the bandwidth.

The bandwidth of the EL5174 and EL5374 depends on the load

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

minimum value that should not be exceeded for optimum

between 500

 to 1k.

The EL5174 and EL5374 have a gain bandwidth product of

predicted by Equation 3:

Driving Capacitive Loads and Cables

The EL5174 and EL5374 can drive a 23pF differential

capacitor in parallel with 1k

 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

 to

50

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

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

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 EL5374 only)

The EL5374 can be disabled and its outputs placed in a high

impedance state. The turn-off time is about 1.2µs and the

turn-on time is about 130ns. 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 EN pin. The applied logic

the amplifier. The amplifier will be disabled when the signal at

Output Drive Capability

The EL5174 and EL5374 have internal short circuit protection. Its

typical short circuit current is ±60mA. 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 EL5174 and EL5374,

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 Equation 4:

Where:

The maximum power dissipation actually produced by an IC is

the total quiescent supply current times the total power supply

voltage, plus the power in the IC due to the load, or as

expressed in Equation 5:

Where:

application

FBP

REF

FBN

Gain BW

200MHz

=



(EQ. 3)

–



JA

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

=

(EQ. 4)

(EQ. 5)

PD

i



V



STOT

V

–

V

O

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



+









=