Ultralow Noise VGA with
Preamplifier and Programmable RIN
Enhanced Product
AD8331-EP
FEATURES
FUNCTIONAL BLOCK DIAGRAM
LON LOP VIP VIN
VCM
HILO
Ultralow noise preamplifier (preamp)
Input voltage noise: 0.74 nV/√Hz typical
Input current noise: 2.5 pA/√Hz typical
−3 dB small signal bandwidth: 120 MHz typical
Low power dissipation: 125 mW typical
Wide gain range with programmable postamp
−4.5 dB to +43.5 dB in low gain mode
7.5 dB to 55.5 dB in high gain mode
Low output-referred noise: 48 nV/√Hz typical
Active input impedance matching
3.5dB OR 15.5dB
V
MID
LNA
19dB
–
ATTENUATOR
VOH
VOL
48dB
21dB
PA
INH
+
CLAMP
LMD
GAIN
VCM
BIAS
VGA BIAS AND
INTERPOLATOR
RCLMP
CONTROL
INTERFACE
AD8331-EP
ENBx GAIN
Optimized for 10-bit/12-bit ADCs
Figure 1.
Selectable output clamping level
Single 5 V supply operation
ENHANCED PRODUCT FEATURES
Supports defense and aerospace applications
(AQEC standard)
Extended industrial temperature range: −55°C to +105°C
Controlled manufacturing baseline
1 assembly/test site
1 fabrication site
Product change notification
Qualification data available on request
The 48 dB gain range of the VGA makes this device suitable for
a variety of applications. Excellent bandwidth uniformity is
maintained across the entire range. The gain control interface
provides precise linear in dB scaling of 50 dB/V for control
voltages between 100 mV and 0.95 V. Factory trim ensures
excellent part to part gain matching.
APPLICATIONS
Radars
Ultrasound and sonar time-gain controls
High performance automatic gain control (AGC) systems
In-phase quadrature (I/Q) signal processing
High speed ADC drivers
Differential signal paths result in superb second- and third-
order distortion performance and low crosstalk.
The low output referred noise of the VGA is advantageous in
driving high speed differential analog-to-digital converters
(ADCs). The gain of the post amplifier (PA) can be pin selected
to 3.5 dB or 15.5 dB to optimize gain range and output noise for
12-bit or 10-bit converter applications. The output can be limited to
a user selected clamping level, preventing input overload to a
subsequent ADC. An external resistor adjusts the clamping level.
GENERAL DESCRIPTION
The AD8331-EP is a single-channel, ultralow noise, linear in dB,
variable gain amplifier (VGA). Optimized for ultrasound
systems, the device is usable as a low noise variable gain element
at frequencies up to 120 MHz.
Included in the channel are an ultralow noise preamp (LNA), an
X-AMP® VGA with 48 dB of gain range, and a selectable gain
postamp with adjustable output limiting. The LNA gain is 19 dB
with a single-ended input and differential outputs. Using a single
resistor, the LNA input impedance can be adjusted to match a
signal source without compromising noise performance.
The operating temperature is specified across the −55°C to
+105°C extended industrial range.
Additional application and technical information can be found
in the AD8331 data sheet.
Rev. 0
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