Interference rejection in UWB LNA using front-end triode MOSFET

In this paper, an ultra wide band low noise amplifier (UWB LNA) with new input stage for interference rejection is presented. In this scheme, a common gate front end MOS device in triode mode is used to reject in-band and out-band interferences. Furthermore, advantage of weak inversion mode of MOS device is used. While this stage has no DC power consumption, it is possible to easily reject in band and out band interferences with 12.5 and 9.2 dB, respectively. In order to increase power gain of the circuit two stages are added as an amplifier to the circuit. Also, in order to improve the noise figure (NF) and bandwidth of the circuit, the advantages of thermal noise cancellation technique in the second stage and the series-peaking method in the output buffer are used. The circuit is design in 0.18 μm technology. Simulation results show peak gain of 17.6 dB in the low band (3.1-4.75 GHz) and 15.6 dB in the high band (6.1-10.6 GHz). Minimum NF in mentioned frequency band is 3 and 2.3 dB, respectively. Hence, this circuit rejects in band and out band interferences 15.6 and 11.5 dB, respectively, while UWB LNA consumes 16 mW DC power from 1.8 V. The s₁₁ is less than -9.6 dB over entire bandwidth since worst value of IIP3 over entire bandwidth is -14 dBm which occurs at 10.6 GHz.