Datasheet Analog Devices AD8331

Ultralow Noise VGAs with
Preamplifier and Programmable RIN
AD8331/AD8332/AD8334 Data Sheet
FEATURES FUNCTIONAL BLOCK DIAGRAM Ultrasound and sonar time-gain controls
High performance automatic gain control (AGC) systems
I/Q signal processing
High speed, dual ADC drivers The AD8331/AD8332/AD8334 are single-, dual-, and quadchannel, ultralow noise linear-in-dB, variable gain amplifiers
(VGAs). Optimized for ultrasound systems, they are usable as a
low noise variable gain element at frequencies up to 120 MHz.
Included in each 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 48 dB gain range of the VGA makes these devices 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 40 mV and 1 V. Factory trim ensures excellent
part-to-part and channel-to-channel gain matching. Rev. I HILO
3.5dB OR 15.5dB VMID VOH – 48dB
ATTENUATOR …

Ultralow Noise VGA with
Preamplifier and Programmable RIN
AD8331-EP Enhanced Product FUNCTIONAL BLOCK DIAGRAM 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
Optimized for 10-bit/12-bit ADCs
Selectable output clamping level
Single 5 V supply operation LON LOP VIP HILO VCM VIN VMID LNA 3.5dB OR 15.5dB
VOH –
INH LMD 48dB
ATTENUATOR
+ 19dB VCM
BIAS VGA BIAS AND
INTERPOLATOR 21dB PA
VOL GAIN
CONTROL …