Design of a digitally tunable 5th order GM-C filter using linearized OTA in 90nm CMOS technology

In this paper we present an analog 5^th order GM-S low-pass filter structure using ten identical operational transconductance amplifiers (OTA) for high speed wireless systems. A linear OTA that can be tuned by a single bias current, which is provided by a 5-bit current DAC, was designed. The 3dB cut-off frequency of the filter can be tuned from 6 MHz to 40 MHz. IM3 of the 40 MHz 5th order low-pass filter is -60 dB with 400 mV p-p input voltage, 1.2 V supply voltage, and approximately 8.4 mW power consumption. Layout of the proposed filter occupies 0.07 mm² IC area in 90nm single-poly 9 metal layer CMOS technology. Post-layout simulation waveforms are obtained using Eldo simulation environment of MentorGraphics tool suit.