EL5123, EL5223, EL5323, EL5423

FN7176 Rev 3.00

Page 13 of 17

August 31, 2010

when sourcing, and

when sinking.

where:

i = 1 to Total number of buffers

If we set the Equations 2 and 3 equal to each other, we can

dissipation curves provide a convenient way to see if the

device will overheat. The maximum safe power dissipation can

be found graphically, based on the package type and the

ambient temperature. By using the previous equation, it is a

derating curves.

Unused Buffers

It is recommended that any unused buffer have the input tied to

the ground plane.

Driving Capacitive Loads

The EL5123, EL5223, EL5323, and EL5423 can drive a wide

range of capacitive loads. As load capacitance increases,

however, the -3dB bandwidth of the device will decrease and

the peaking increase. The buffers drive 10pF loads in parallel

with 10k

 with just 1.5dB of peaking, and 100pF with 6.4dB of

peaking. If less peaking is desired in these applications, a

small series resistor (usually between 5

 and 50) can be

placed in series with the output. However, this will obviously

reduce the gain slightly. Another method of reducing peaking is

to add a “snubber” circuit at the output. A snubber is a shunt

load consisting of a resistor in series with a capacitor. Values of

150

 and 10nF are typical. The advantage of a snubber is that

it does not draw any DC load current or reduce the gain.

Power Supply Bypassing and Printed Circuit Board

Layout

As with any high frequency device, good printed circuit board

layout is necessary for optimum performance. Ground plane

construction is highly recommended, lead lengths should be as

short as possible, and the power supply pins must be well

bypassed to reduce the risk of oscillation. For normal single

ground. A 4.7µF tantalum capacitor should then be connected

multiple devices. This same capacitor combination should be

placed at each supply pin to ground if split supplies are to be

used.

iV



S





–

+



=

(EQ. 3)