Linearized low-noise cascode RF amplifiers using a novel distortion-cancelling bias scheme

A distortion-cancelling bias scheme is presented that improves the linearity of RF amplifiers connected in cascode topology. The bias method involves stacking one bias circuit on top another bias circuit so that the same current flows through the bias circuit. In this way, the nonlinearity of the gain and cascode amplifying devices can be cancelled out by the dynamic variations of the currents and voltages set by the bias circuits. Bandwidth is wide due to the absence of frequency dependent elements. Noise performance is also not impacted. The technique was implemented in different circuits fabricated on enhancement-mode pHEMT technology. Measured results from different designs confirm the scalability and bandwidth of the distortion-cancelling technique. At 5V and 134mA bias, up to 45.5dbm of OIP3 was achieved. A low-noise, low-power design biased at 2.7V and 5.5mA supply exhibited IIP3 of −1dbm with 0.88dB noise and 19dB gain.