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) [1–5]. A 650 MHz current-mode seventh-order 0.05° equiripple linear phase low-pass filter for computer hard disk read/write channels with data rates up to 1Gbit/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 0.18μm CMOS process, the dynamic range at 1% THD of the filter is 48dB, cut-off frequency can be tuned from 590MHz to 690MHz, group delay ripple is about 5%, and power consumption is 370mW from supply voltage of 2.5V.