The AD604 is an ultralow noise, very accurate, dual-channel, linear-in-dB variable gain amplifier (VGA) optimized for time-based variable gain control in ultrasound applications; however, it supports any application requiring low noise, wide bandwidth, variable gain control. Each channel of the AD604 provides a 300k? input resistance and unipolar gain control for ease of use. User determined gain ranges, gain scaling (dB/V), and dc level shifting of output further optimize performance.