A CMOS 650 MHz seventh-order current-mode 0.05° equiripple linear phase filter

Read/write channels for hard disk drives (HDD) require high-frequency continuous time filters (CTF). A 650 MHz current-mode seventh-order 0.05deg equiripple linear phase low-pass filter for computer hard disk read/write channels with data rates up to 1 Gbit/s is presented in this paper. It is implemented in CMOS using a leap-frog multiple loop feedback structure. The operational transconductance amplifier (OTA) used is based on a differential pair and uses source degeneration to achieve linearization and tuning. Simulated using a standard 0.18 mum CMOS process, the dynamic range at 1% THD of the filter is 48 dB, cut-off frequency can be tuned from 590 MHz to 690 MHz, group delay ripple is about 5%, and power consumption is 370 mW from supply voltage of 2.5 V.