GENERAL DESCRIPTION

The AD8331/AD8332/AD8334 are single-, dual-, and quad channel 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 preamplifier (LNA), an X-AMP® VGA with 48 dB of gain range, and a selectable gain postamplifier 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.

FEATURES

Ultralow noise preamplifier

   Voltage noise = 0.74 nV/√Hz

   Current noise = 2.5 pA/√Hz

3 dB bandwidth

   AD8331: 120 MHz

   AD8332, AD8334: 100 MHz

Low power

   AD8331: 125 mW/channel

   AD8332, AD8334: 145 mW/channel

Wide gain range with programmable postamp

   −4.5 dB to +43.5 dB

   +7.5 dB to +55.5 dB

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

AD8332 and AD8334 available in lead frame chip scale package

APPLICATIONS

Ultrasound and sonar time-gain controls

High performance AGC systems

I/Q signal processing

High speed, dual ADC drivers