The AD8331 is a single channel, ultralow noise, linear-in-dB, variable gain amplifier (VGA). Optimized for ultrasound systems, it is usable as a low noise variable gain element at frequencies up to 120 MHz.Included is 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.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. Differential signal paths result in superb second- and third-order distortion performance and low crosstalk.The operating temperature range is -40°C to +85°C. The AD8331 is available in a 20-lead QSOP package.The AD8331 is a single version of the dual AD8332 and quad AD8334.For information on specs, see the AD8331/AD8332/AD8334 datasheet.ApplicationsUltrasound and sonar time-gain controlsHigh performance automatic gain control (AGC) systemsI/Q signal processingHigh speed, dual ADC drivers