Multi-Standard Lowpass Filter for Baseband Chain Using Highly Linear Digitally Programmable OTA

In this paper, a digital programmable balanced OTA is proposed. The proposed OTA employs three linearization techniques which are the source degeneration, double differential pair (DDP) and the adaptive biasing. The programmability concept is achieved by using two current division networks (CDNs). The third-order harmonic distortion (HD3) remains below -65 dB up to 0.4 V differential input voltage at 1.2 V supply voltage. A 4th-order Butterworth lowpass filter is designed, for baseband section, using the proposed DPOTA. The filter exhibits a cutoff frequency tuning range from 1 MHz to 10.2 MHz, thus, it covers Bluetooth, UMTS, DVB-H and IEEE 802.11a/g standards. The DPOTA and the filter are designed and simulated in 90 nm CMOS technology with LTspice simulator.