General Description
The MAX2035 8-channel variable-gain amplifier (VGA) is designed for high linearity, high dynamic range, and low-noise performance targeting ultrasound imaging and Doppler applications. Each amplifier features differential inputs and outputs and a total gain range of typically 50dB. In addition, the VGAs offer very low output-referred noise performance suitable for interfacing with 10-bit ADCs.
The MAX2035 VGA is optimized for less than ±0.5dB absolute gain error to ensure minimal channel-to-channel ultrasound beamforming focus error. The device’s differential outputs are designed to directly drive ultra-sound ADCs through an external passive anti-aliasing filter. A switchable clamp is also provided at each amplifier’s outputs to limit the output signals, thereby prevent ing ADC overdrive or saturation.

Features
♦ 8-Channel Configuration
♦ High Integration for Ultrasound Imaging
   Applications
♦ Pin Compatible with the MAX2036 Ultrasound
   VGA Plus CW Doppler Beamformer
♦ Maximum Gain, Gain Range, and Output-Referred
   Noise Optimized for Interfacing with 10-Bit ADCs
   Maximum Gain of 39.5dB
   Total Gain Range of 50dB
   60nV/√Hz Ultra-Low Output-Referred Noise at
   5MHz
   Pin-for-Pin 12-Bit Compatibility Supported By
   MAX2037/MAX2038
♦ ±0.5dB Absolute Gain Error
♦ Switchable Output VGA Clamp Eliminating ADC
   Overdrive
♦ Fully Differential VGA Outputs for Direct ADC
   Drive
♦ Variable Gain Range Achieves 50dB Dynamic
   Range
♦ -62dBc HD2 at VOUT = 1.5VP-P and fIN = 5MHz
♦ Two-Tone Ultrasound-Specific* IMD3 of -52dBc at
   VOUT = 1.5VP-P and fIN = 5MHz
♦ 127mW Consumption per Channel

Applications
   Ultrasound Imaging Sonar