lmh6622mmx National Semiconductor Corporation, lmh6622mmx Datasheet - Page 12

• Manufacturer Part Number: lmh6622mmx
• Description: Dual Wideband, Low Noise, 160mhz, Operational Amplifiers
• Manufacturer: National Semiconductor Corporation

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Test Circuits
DSL Receive Channel Applications
The LMH6622 is a dual, wideband operational amplifier de-
signed for use as a DSL line receiver. In the receive band of
a Customer Premises Equipment (CPE) ADSL modem it is
possible that as many as 255 Discrete Multi-Tone (DMT)
QAM signals will be present, each with its own carrier fre-
quency, modulation, and signal level. The ADSL standard
requires a line referred noise power density of -140dBm/Hz
within the CPE receive band of 100KHz to 1.1MHz. The CPE
driver output signal will leak into the receive path because of
full duplex operation and the imperfections of the hybrid
coupler circuit. The DSL analog front end must incorporate a
5) Multitone Power Ratio, R
(Continued)
437Ω
F
= 500Ω, R
G
FIGURE 1. ADSL Signal Description
= 174Ω, R
20029255
L
=
12
receiver pre-amp which is both low noise and highly linear
for ADSL-standard operation. The LMH6622 is designed for
the twin performance parameters of low noise and high
linearity.
Applications ranging from +5V to +12V or
fully supported by the LMH6622. In Figure 2, the LMH6622 is
used as an inverting summing amplifier to provide both
received pre-amp channel gain and driver output signal can-
cellation, i.e., the function of a hybrid coupler.
20029223
±
2.5V to
±
6V are