Active inductor for power-supply decoupling in mixed signal systems

A CMOS active inductor circuit intended for power-supply decoupling application is presented. The idea is to minimize the switching noise generated by the digital part of a mixed-signal integrated circuit. This is essential when sensitive analog circuits share the same power supply bus with a digital signal processor. In systems with a single clock, the frequency components of the switching noise are the clock frequency and its harmonics. As clock frequencies exceed 1 GHz, the circuit for filtering the switching noise needs only a modest amount of chip area and thus it can be integrated. Simulation results of the proposed circuit using GSMC 0.18 micron CMOS models are used to arrive at the basis for the design of a decoupling scheme.