VCA
261
6
VCA2616
VCA2611
SBOS234E – MARCH 2002 – REVISED NOVEMBER 2004
Dual, Variable-Gain Amplifier
with Low-Noise Preamp
FEATURES
q
LOW-NOISE PREAMP:
– Low Input Noise: 0.95nV/
√Hz
– Active Termination Noise Reduction
– Switchable Termination Value
– 80MHz Bandwidth
– 5dB to 25dB Gain
– Differential In and Out
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LOW-NOISE VARIABLE GAIN AMPLIFIER:
– Low-Noise VCA
– Up to 40dB Gain Range
– 40MHz Bandwidth
– Differential In and Out
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LOW CROSSTALK: 66dB at Max Gain, 5MHz
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HIGH-SPEED VARIABLE GAIN ADJUST
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SWITCHABLE EXTERNAL PROCESSING
DESCRIPTION
The VCA2616 and VCA2611 are dual, Low-Noise Preamplifiers
(LNP), plus low-noise Variable Gain Amplifiers (VGA). The
VCA2611 is an upgraded version of the VCA2616. The only
difference between the VCA2616 and the VCA2611 is the input
structure to the LNP. The VCA2616 is limited to –0.3V negative-
going input spikes; the VCA2611 is limited to –2.0V negative-
going input spikes. This change allows the user to use slower
and less expensive input clamping diodes prior to the LNP input.
In some designs, input clamping may not be required.
The combination of Active Termination (AT) and Maximum
Gain Select (MGS) allow for the best noise performance. The
VCA2616 and VCA2611 also feature low crosstalk and out-
standing distortion performance.
The LNP has differential input and output capability and is
strappable for gains of 5dB, 17dB, 22dB, or 25dB. Low input
impedance is achieved by AT, resulting in as much as a 4.6dB
improvement in noise figure over conventional shunt termina-
tion. The termination value can also be switched to accommo-
date different sources. The output of the LNP is available for
external signal processing.
The variable gain is controlled by an analog voltage whose
gain varies from 0dB to the gain set by the MGS. The ability
to program the variable gain also allows the user to optimize
dynamic range. The VCA input can be switched from the LNP
to external circuits for different applications. The output can be
used in either a single-ended or differential mode to drive high-
performance Analog-to-Digital (A/D) converters, and is cleanly
limited for optimum overdrive recovery.
Maximum Gain Select
VCA
CNTL
MGS
1
MGS
2
MGS
3
APPLICATIONS
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ULTRASOUND SYSTEMS
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WIRELESS RECEIVERS
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TEST EQUIPMENT
FB
CNTL
RF
2
RF
1
LNP
OUT
N VCA
IN
N
FBSW
FB
VCA2616
(1 of 2 Channels)
Analog
Control
Maximum Gain
Select
The combination of low noise, gain, and gain range program-
mability makes the VCA2616 and VCA2611 versatile building
blocks in a number of applications where noise performance
is critical. The VCA2616 and VCA2611 are available in a
TQFP-48 package.
Input
LNP
IN
P
VCA
OUT
N
LNP
GS1
LNP
GS2
LNP
GS3
LNP
IN
N
VCA
OUT
P
Programmable
Gain Amplifier
24 to 45dB
LNP
Gain
Set
Low Noise
Preamp
5dB to 25dB
Voltage
Controlled
Attenuator
LNP
OUT
P VCA
IN
P
SEL
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
All trademarks are the property of their respective owners.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of Texas Instruments
standard warranty. Production processing does not necessarily include
testing of all parameters.
Copyright © 2002-2004, Texas Instruments Incorporated
www.ti.com
TAOS [ TEXAS ADVANCED OPTOELECTRONIC SOLUTIONS ]
