A Low-Power CMOS VGA for 50Mb/s Disk Drive Read Channels

We describe an all CMOS variable gain ampliier (VGA) suitable for use in disk drive read channels. The VGA maintains a 3dB bandwidth greater than 85 MHz throughout its gain range. This ensures good phase linearity for data transfer rates of up to 50Mb/s. The VGA provides a 25dB gain variation along an ideal exponential gain to control voltage curve and 30dB of gain control if ideal exponential characteristics is not absolutely necessary. The VGA achieves the necessary exponential gain to control voltage characteristics intrinsically using only MOS transistors as a single unit to reduce power and area consumption. Overall power consumption is less than 10mW for the VGA circuit excluding the oo-chip buuer circuits.