LT6600-20 Datasheet, PDF (1/12 Pages) Linear Technology – Very Low Noise, Differential Amplifier and 20MHz Lowpass Filter

LT6600-20
Very Low Noise, Differential
Amplifier and 20MHz Lowpass Filter
FEATURES
s _{Programmable Differential Gain via Two External}
Resistors
s _{Adjustable Output Common Mode Voltage}
s _{Operates and Specified with 3V, 5V, ±5V Supplies}
s _{0.5dB Ripple 4th Order Lowpass Filter with 20MHz}
Cutoff
s _{76dB S/N with 3V Supply and 2VP-P Output}
s _{Low Distortion, 2VP-P, 800Ω Load}
2.5MHz: 83dBc 2nd, 88dBc 3rd
20MHz: 63dBc 2nd, 64dBc 3rd
s _{Fully Differential Inputs and Outputs}
s _{SO-8 Package}
s _{Compatible with Popular Differential Amplifier}
Pinouts
U
APPLICATIO S
s _{High Speed ADC Antialiasing and DAC Smoothing in}
Networking or Cellular Base Station Applications
s _{High Speed Test and Measurement Equipment}
s _{Medical Imaging}
s _{Drop-in Replacement for Differential Amplifiers}
, LTC and LT are registered trademarks of Linear Technology Corporation.
DESCRIPTIO
The LT^®6600-20 combines a fully differential amplifier
with a 4th order 20MHz lowpass filter approximating a
Chebyshev frequency response. Most differential amplifi-
ers require many precision external components to tailor
gain and bandwidth. In contrast, with the LT6600-20, two
external resistors program differential gain, and the filter’s
20MHz cutoff frequency and passband ripple are internally
set. The LT6600-20 also provides the necessary level
shifting to set its output common mode voltage to accom-
modate the reference voltage requirements of A/Ds.
Using a proprietary internal architecture, the LT6600-20
integrates an antialiasing filter and a differential amplifier/
driver without compromising distortion or low noise
performance. At unity gain the measured in band
signal-to-noise ratio is an impressive 76dB. At higher
gains the input referred noise decreases so the part can
process smaller input differential signals without signifi-
cantly degrading the output signal-to-noise ratio.
The LT6600-20 also features low voltage operation. The
differential design provides outstanding performance for
a 2V_P-P signal level while the part operates with a single 3V
supply.
The LT6600-20 is packaged in an SO-8 and is pin compat-
ible with stand alone differential amplifiers.
TYPICAL APPLICATIO
LT6600-20
5V
0.1µF
R_IN
402Ω
1
3
–
7
+⁴
V_MID
0.01µF
V_IN
2
8
V_OCM
+
–
5
R_IN
6
402Ω
49.9Ω
49.9Ω
GAIN = 402Ω/R_IN
A/D
LTC1748
5V
+
18pF
A_IN
–
V_CM
V⁺
D_OUT
V^–
1µF
66002 TA01a
An 8192 Point FFT Spectrum
0
–10
INPUT 5.9MHz
2V_P-P
–20
f_SAMPLE = 80MHz
–30
–40
–50
–60
–70
–80
–90
–100
–110
–120
0
10
20
30
40
FREQUENCY (MHz)
66002 TA01b
66002f
1