Noise Canceling Balun-LNA with Enhanced IIP2 and IIP3 for Digital TV Applications

An inductorless low noise amplifier (LNA) with active balun for digital TV (DTV) applications is presented. The LNA exploits a noise cancellation technique which allows for simultaneous wide-band impedance matching and low noise design. The matching and amplifier stages in the LNA topology perform single-ended to differential signal conversion with balanced output. The second and third-order nonlinearity of the individual amplifiers as well as the distortion caused by the interaction between the stages are suppressed to achieve high IIP2 and IIP3. A method for intrinsic cancellation of the second-order interaction is employed to reduce the dependence of the IIP3 on the frequency spacing between the interfering signals in the two-tone test of DTV tuners. Fabricated in a 0.18µm CMOS technology, the LNA core size is 0.21mm2. Measurements show that the LNA IIP3 and IIP2 are +12dBm and +21dBm, respectively. The IIP3 variation is less than 5dB in the 10MHz to 200MHz frequency spacing range. A voltage gain of 14.5dB and a noise figure below 4dB are achieved in a frequency range from 100MHz to 1GHz. The LNA consumes 11mA from a 1.8V supply voltage.