A CMOS Low Power Current Source Tunable Inductor With 80% Tuning Range for RFIC

This article describes a novel Low Power Current Source Tunable Inductor (LPCSTI) for CMOS Radio Frequency Integrated Circuits (RFIC). The LPCSTI comprises a deep triode common source transistor, a stabilizer resistor and a coupling capacitor which is capable to increase the physical inductance value up to 80% from its default value thus achieving higher inductance per area. Integration of the tuner to a physical inductor of 1.2 nH increases the inductance value up to 2.2 nH at 2.5 GHz, contributing to an area reduction of 52%. The LPCSTI is implemented in a single stage CMOS 180 nm power amplifier (PA) and tested. The tunability property of the LPCSTI allows the performance of the LPCSTI-PA to be adjusted and makes it resilient to process variations, thus enhances production yield. The LPCSTI-PA achieved a maximum output power of 15 dBm as well as peak efficiency of 45%. Measurement on 10 sample dice show that the efficiency of the LPCSTI-PA can be maintained to be more than 20% at maximum linear output power.