ADI AD8331ARQZ-RL

The AD8331/AD8332/AD8334 are single-channel/dual-channel/quad-channel, ultralow noise, linear-in-dB variable gain amplifiers (VGAs) optimized for ultrasound systems, usable as low-noise variable gain elements operating at frequencies up to 120 MHz. Each channel integrates an ultralow noise preamplifier (LNA), an X-AMP VGA with 48 dB gain range, and an optional gain postamplifier with adjustable output limiting. The LNA provides 19 dB gain with single-ended input and differential output. LNA input impedance can be adjusted using a resistor to match the signal source without degrading noise performance. The 48 dB VGA gain range makes these devices suitable for a wide variety of applications. Bandwidth consistency is maintained excellently across the entire gain range. For control voltages in the 40 mV to 1 V range, the gain control interface provides precise linear-in-dB adjustment of 50 dB/V. Factory trimming ensures excellent gain matching between devices and channels. The differential signal path delivers superior second- and third-order distortion performance and low crosstalk. The low output-referred noise of the VGA is advantageous when driving high-speed differential ADCs. Postamplifier gain is pin-selectable at 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 clamp level to prevent overloading the input of a downstream ADC. An external resistor sets the clamp level. Operating temperature range is -40°C to +85°C. The AD8331 is available in a 20-lead QSOP package, the AD8332 in 28-lead TSSOP and 32-lead LFCSP packages, and the AD8334 in a 64-lead LFCSP package.

• Ultra-low noise preamplifier
• Voltage noise = 0.74 nV/√Hz
• Current noise = 2.5 pA/√Hz
• Low power consumption
• AD8331: 125 mW per channel
• AD8332, AD8334: 145 mW per channel
• Programmable postamplifier for wide gain range
• LO gain mode: −4.5 dB to +43.5 dB
• HI gain mode: 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 ADC
• Selectable output clamp level
• 5 V single-supply operation
• AD8332 and AD8334 available in pin-compatible chip-scale package

• Ultrasonic and sonar time gain control
• High-performance AGC systems
• I/Q signal processing
• High-speed, dual-channel ADC driver