LT6600-2.5
Very Low Noise, Differential
Amplifier and 2.5MHz Lowpass Filter
FEATURES
DESCRIPTION
The LT®6600-2.5 combines a fully differential amplifier
with a 4th order 2.5MHz lowpass filter approximating a
Chebyshev frequency response. Most differential ampli-
fiers require many precision external components to tail
or gain and bandwidth. In contrast, with the LT6600-2.5,
two external resistors program differential gain, and the
filter’s 2.5MHz cutoff frequency and passband ripple are
internallyset. TheLT6600-2.5alsoprovidesthenecessary
levelshiftingtosetitsoutputcommonmodevoltagetoac-
commodate the reference voltage requirements of A/Ds.
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0.6dB ꢀMaxꢁ ꢂipple 4th Order Lowpass Filter with
2.5MHz Cutoff
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Programmable Differential Gain via Two External
ꢂesistors
Adjustable Output Common Mode Voltage
Operates and Specified with 3V, 5V, 5V Supplies
86dB S/N with 3V Supply and 1V
Low Distortion, 1V
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Output
ꢂMS
, 800Ω Load
ꢂMS
1MHz: 95dBc 2nd, 88dBc 3rd
Fully Differential Inputs and Outputs
Compatible with Popular Differential Amplifier
Pinouts
SO-8 and DFN-12 Packages
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Using a proprietary internal architecture, the LT6600-2.5
integrates an antialiasing filter and a differential ampli-
fier/driver without compromising distortion or low noise
performance. At unity gain the measured in band signal-
to-noise ratio is an impressive 86dB. At higher gains the
input referred noise decreases so the part can process
smaller input differential signals without significantly
degrading the output signal-to-noise ratio.
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APPLICATIONS
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High Speed ADC Antialiasing and DAC Smoothing in
Networking or Cellular Basestation Applications
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High Speed Test and Measurement Equipment
The LT6600-2.5 also features low voltage operation. The
differentialdesignprovidesoutstandingperformancefora
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Medical Imaging
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Drop-in ꢂeplacement for Differential Amplifiers
4V signal level while the part operates with a single 3V
P-P
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
supply. The LT6600-2.5 is available in SO-8 and DFN-12
packages.
For similar devices with higher cutoff frequency, refer
to the LT6600-5, LT6600-10, LT6600-15 and LT6600-20
data sheets.
(S8 Pin Numbers Shown)
TYPICAL APPLICATION
DAC Output Filter
DAC Output Spectrum
LT6600-2.5 Output Spectrum
0
–10
–20
–30
–40
–50
–60
–70
–80
–90
0
–10
–20
–30
–40
–50
–60
–70
–80
–90
5V
0.1μF
5V
BASEBAND SIGNAL
52.3Ω
52.3Ω
1580Ω
1580Ω
3
1
LADCOM
–
4
+
–
V
I
OUT
7
2
+
OUT A
16-BIT 4kHz to 2.5MHz
DISCꢂETE MULTI-TONE
SIGNAL AT 50MSPS
LT6600-2.5
LTC1668
DAC OUTPUT IMAGE
I
V
–
6
OUT B
8
OUT
5
+
CLK
0.1μF
–5V 50MHz
–5V
660025 TA01a
0
12 24 36 48 60 72 84 96 108 120
0
12 24 36 48 60 72 84 96 108 120
FꢂEQUENCY ꢀMHzꢁ
FREQUENCY (MHz)
660025 TA01b
660025 TA01c
660025fe
1