11

FN7383.4

May 4, 2007

transfer function contribute to even higher closed loop

bandwidths. For example, the EL5134, EL5135, EL5234 and

EL5235 have a -3dB bandwidth of 650MHz at a gain of 5,

dropping to 150MHz at a gain of 10. It is important to note

that the EL5134, EL5135, EL5234 and EL5235 is designed

so that this “extra” bandwidth in low-gain application does

not come at the expense of stability. As seen in the typical

performance curves, the EL5134, EL5135, EL5234 and

EL5235 in a gain of only 5 exhibited 0.2dB of peaking with a

500

Ω load.

Output Drive Capability

The EL5134, EL5135, EL5234 and EL5235 are designed to

signal into a 500

Ω load. This high output drive capability

makes the EL5134, EL5135, EL5234 and EL5235 and ideal

choice for RF, IF, and video applications. Furthermore, the

EL5134, EL5135, EL5234 and EL5235 are current-limited at

their outputs, allowing them to withstand momentary short to

ground. However, the power dissipation with output-shorted

cannot exceed the power dissipation capability of the

package.

Driving Cables and Capacitive Loads

Although the EL5134, EL5135, EL5234 and EL5235 are

designed to drive low impedance load, capacitive loads will

decreases the amplifiers’ phase margin. As shown in the

performance curves, capacitive load can result in peaking,

overshoot and possible oscillation. For optimum AC

performance, capacitive loads should be reduced as much

as possible or isolated with a series resistor between 5

Ω to

20

Ω. When driving coaxial cables, double termination is

always recommended for reflection-free performance. When

properly terminated, the capacitance of the coaxial cable will

not add to the capacitive load seen by the amplifier.

Disable/Power-Down

The EL5134 and EL5234 amplifiers can be disabled placing

their outputs in a high impedance state. When disable, each

amplifier current is reduced to 12uA. The EL5134 and

EL5234 are disabled when their CE pins are pulled up to

within 1V of the power suply. Similarly, the amplifiers are

enabled by floating or pulling its CE pin to at least 3V below

the positive supply. For +/-5V supply, this means that

EL5134 and EL5234 amplifiers will be enabled when CE is

2V or less, and disabled when CE is above 4V. Although the

logic levels are not stardard TTL, this choice of logic

voltages allows the EL5134 and EL5234 to be enabled by

typing CE to ground, even in 5V single supply applications.

The CE pin can be driveing from CMOS outputs.

Supply Voltage Range and Single-Supply

Operation

The

EL5134, EL5135, EL5234 and EL5235 have been

designed to operate with supply voltages having a span of

greater than 5V and less than 12V. In practical terms, this

means that they will operate on dual supplies ranging from

±2.5V to ±6V. With single-supply, the

EL5134, EL5135,

EL5234 and EL5235 will operate from 5V to 12V. To prevent

internal circuit latch-up, the slew rate between the negative

and positve supplies must be less than 1V/nS.

As supply voltages continue to decrease, it becomes

necessary to provide input and output voltage ranges that

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

EL5134, EL5135, EL5234 and EL5235 have an input range

which extends to within 2V of either supply. So, for example,

on ±5V supplies, the

EL5134, EL5135, EL5234 and EL5235

have an input range which spans ±3V. The output range of

the

EL5134, EL5135, EL5234 and EL5235 is also quite

large, extending to within 2V of the supply rail. On a ±5V

supply, the output is therefore capable of swinging from

-3.1V to +3.1V. Single-supply output range is larger because

of the increased negative swing due to the external pull-

down resistor to ground.

Power Dissipation

With the wide power supply range and large output drive

capability of the EL5134, EL5135, EL5234 and EL5235, it is

possible to exceed the 150°C maximum junction

temperatures under certain load and power-supply

conditions. It is therefore important to calculate the

to determine if power supply voltages, load conditions, or

package type need to be modified for the EL5134, EL5135,

EL5234 and EL5235 to remain in the safe operating area.

These parameters are related as follows:

where:

where:

•

application

Power Supply Bypassing And Printed Circuit

Board Layout

As with any high frequency devices, good printed circuit

board layout is essential for optimum performance. Ground

T

JMAX

T

MAX

θ

()

+

=

PD

MAX

2*V

S

I

SMAX

V

S

(

- V

V

OUTMAX

R

L

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

×

+

×

=

EL5134, EL5135, EL5234, EL5235