The AD8334 is an ultralow noise, quad channel linear-in-dB variable gain amplifier (VGA). Although optimized for ultrasound systems, it may be used as a low noise variable gain control in any application whose operating frequency is less than 100 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. Differential signal paths result in superb second- and third-order distortion performance and low crosstalk.The AD8334 is a quad version of the single AD8331 and dual AD8332.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