FN7122 Rev 2.00

Page 8 of 10

March 26, 2007

EL1510

Intersil products are manufactured, assembled and tested utilizing ISO9001 quality systems as noted

in the quality certifications found at www.intersil.com/en/support/qualandreliability.html

Intersil products are sold by description only. Intersil may modify the circuit design and/or specifications of products at any time without notice, provided that such

modification does not, in Intersil's sole judgment, affect the form, fit or function of the product. Accordingly, the reader is cautioned to verify that datasheets are

current before placing orders. Information furnished by Intersil is believed to be accurate and reliable. However, no responsibility is assumed by Intersil or its

subsidiaries for its use; nor for any infringements of patents or other rights of third parties which may result from its use. No license is granted by implication or

otherwise under any patent or patent rights of Intersil or its subsidiaries.

For information regarding Intersil Corporation and its products, see www.intersil.com

For additional products, see www.intersil.com/en/products.html

© Copyright Intersil Americas LLC 2004-2007. All Rights Reserved.

All trademarks and registered trademarks are the property of their respective owners.

Capacitance at the Inverting Input

Due to the topology of the current feedback amplifier, stray

capacitance at the inverting input will affect the AC and

transient performance of the EL1510 when operating in the

non-inverting configuration.

In the inverting gain mode, added capacitance at the

inverting input has little effect since this point is at a virtual

ground and stray capacitance is therefore not “seen” by the

amplifier.

Feedback Resistor Values

The EL1510 has been designed and specified with

RF=1.5k for AV=+5. This value of feedback resistor yields

extremely flat frequency response with no peaking out to

40MHz. As is the case with all current feedback amplifiers,

wider bandwidth, at the expense of slight peaking, can be

obtained by reducing the value of the feedback resistor.

Inversely, larger values of feedback resistor will cause rolloff

to occur at a lower frequency. See the curves in the Typical

Performance Curves section which show 3dB bandwidth and

peaking vs frequency for various feedback resistors and

various supply voltages.

Bandwidth vs Temperature

Whereas many amplifiers’ supply current and consequently

3dB bandwidth drop-off at high temperature, the EL1510

was designed to have little supply current variations with

temperature. An immediate benefit from this is that the 3dB

bandwidth does not drop off drastically with temperature.

Supply Voltage Range and Operation

The EL1510 has been designed to operate with supply

voltages from ±2.5V to ±12V. If a single supply is desired,

values from +5V to +24V can be used as long as the input

common mode range is not exceeded. When using a single

supply, be sure to either 1) DC bias the inputs at an

appropriate common mode voltage and AC couple the

signal, or 2) ensure the driving signal is within the common

mode range of the EL1510.

ADSL CPE Applications

The EL1510 is designed as a line driver for ADSL CPE

modems. It is capable of outputting 400mA of output current

with a typical supply voltage headroom of 1.8V. It can

achieve -85dBc of distortion at low 7.5mA of supply current

per amplifier.

The average line power requirement for the ADSL CPE

application is 13dBm (20mW) into a 100

 line. The average

line voltage is 1.41VRMS. The ADSL DMT peak to average

ratio (crest factor) of 5.3 implies peak voltage of 7.5V into the

line. Using a differential drive configuration and transformer

coupling with standard back termination, a transformer ratio

of 1:1 is selected. The circuit configuration is as shown

below.

-

+

-

+

100

TX1

1:1

50

50

1.5k

1.5k

300



AFE