A 2 V 0.25µm CMOS 250 MHz fully-differential seventh-order equiripple linear phase LF filter

A fully-differential seventh-order 0.05° equiripple linear phase low-pass filter based on multiple loop feedback (MLF) leapfrog (LF) topology is presented for read/write channels. The filter is designed and simulated with the proposed fully balanced, highly linear operational transconductance amplifier (OTA). This OTA contains two complementary differential cross-coupled input pairs and a pair of regulated cascode output in order to achieve both lowdistortion and wide dynamic rang in high-frequency operation. Simulations in 0.25μm CMOS show that the cutoff frequency of the low pass filter without and with gain boost ranges from 50 to 150MHz and 65 to 250MHz respectively, dynamic-range is over 65dB and total harmonic distortion is less than 40dB. The group delay ripple is less than 5% for frequencies up to 1.5 times of the cutoff frequency, and for a 2-volt power supply, the maximum power consumption is 216mW.