This paper presents a highly linear Gilbert cell OTA by cancelling the second order transconductance derivative (gm″) of nMOS transistors near threshold voltage using the technique of multiple gated transistors. This gives rise to 5dB improvement in IIP3 of OTA, using a 0.13µm CMOS technology with 1.2V supply. Simulation results and analytical relations for THD and IIP3 in OTA illustrate the tradeoffs between linearity, bandwidth, and power dissipation. System level simulation of a non-coherent UWB receiver, with this OTA as a Gm-C integrator in receiver structure, illustrates an improvement of BER from 3e^-2 to 1e^-3. The power consumption, IIP3, and transconductance in OTA are 0.62mW, 20.5dBm, and 156µA/V, respectively.