EL2004 datasheet(9/16 Pages) ELANTEC

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EL2004EL2004C

350 MHz FET Buffer

Circuit Operation

Contd

Increasing Operating Voltage

and Reducing Thermal Tail

When driving heavy loads the changing dissipa-

tion in the output transistors can sometimes

cause temperature gradients in the circuit which

cause a shift in offset voltage and the phenome-

non known as ‘‘thermal tail’’ Bootstrapping the

output as illustrated substantially reduces the

power in the output transistors and mitigates the

effect

High Voltage Inputs can be Accommodated

with Bootstrapped Supplies

2004 – 13

Hardware

In order to utilize the full drive capabilities of the

EL2004 it should be mounted with a heatsink

particularly for extended temperature operation

Suitable heatsinks include Thermalloy 2240A

(33 CW)

Wakefield

215CB

(30 CW)

and

IERC-UP-TO-848CB (15 CW)

The case is isolated from the circuit and may be

connected to system chassis Sockets are not rec-

ommended as they add substantial inductance

and capacitance which impair the performance of

the device However for test purposes they are

unavoidable and precautions such as shielding in-

put from output are suggested

General Application Suggestions

Video DAC Buffer

Many of the available video D to A converters

are unable to directly drive 50

X or 75X cables

The EL2004’s excellent phase linearity at video

frequencies make it an ideal solution In critical

applications or where line termination is not con-

trolled a matching pad should be used as shown

The capacitor should be adjusted for optimum

pulse response If properly layed out this circuit

will not overshoot

Video DAC Buffer

2004 – 14

Impedance Matching

The EL2004 provides power gain and isolation

between source and load when used as an active

tap or impedance matching device as illustrated

here In this example there is no output match-

ing pad between the 2004 and the 75

X line Such

matching is not needed when the distant end of

the cable is properly terminated as there is no

reflected signal to worry about and the 2004 iso-

lates the source This technique allows the full

output voltage of the EL2004 to be applied to the

load

Impedance Converter

2004 – 15

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