Monolithic Transformers and Their Application in a Differential CMOS RF Low-Noise Amplifier

A 900 MHz low-noise amplifier (LNA) utilizing three monolithic transformers to implement on-chip tuning networks and requiring no external components has been integrated in 2.88 mm in a standard digital 0.6 m CMOS process. A bias current reuse technique is employed to reduce power dissipation, and process-, voltage-, and temperature-tracking biasing techniques are used. At 900 MHz, the LNA dissipates 18 mW from a single 3 V power supply and provides 4.1 dB noise figure, 12.3 dB power gain, 33.0 dB reverse isolation, and an input 1-dB compression level of 16 dBm. Analysis and modeling considerations for silicon-based monolithic transformers are presented, and it is shown that a monolithic transformer occupies less die area and provides a higher quality factor than two independent inductors with the same effective inductance in differential applications.