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