A 2 V 0.25 μm 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 a fully balanced, highly linear operational transconductance amplifier (OTA). The proposed OTA contains two complementary differential cross-coupled input pairs and a pair of regulated cascode outputs in order to achieve both low-distortion and wide dynamic range in high-frequency operation. Simulations in 0.25 μm CMOS show that the cutoff frequency of the low pass filter without and with gain boost ranges from 50 to 150 MHz and 65 to 250 MHz respectively, dynamic-range is over 65 dB and total harmonic distortion is less than 40 dB. The group delay ripple is less than 5% for frequencies up to 1.5 times the cutoff frequency, and for a 2-volt power supply, the maximum power consumption is 216 mW.