High Frequency Active Inductor

An integrated inductor capable of operating at gigahertz (1 billion Hz) frequencies and above is a critical element in oscillators, filters, and wide-band low-noise amplifiers, (LNAs). The main applications are radio-frequency (RF) communication and high-speed data processing integrated circuits, such as those in cellular phones, wireless network cards, and broadband transceivers.

 

Active integrated inductors are an alternative to passive inductors when the need for maximum selectivity (Q) prohibits the use of a passive inductor or when die area is limited.  The key innovations of this particular design are independent electronic frequency and Q tuning, minimum transistor count, small area and integration in a digital semiconductor process.  They occupy as little as 2-10% of the area of a passive inductor and combine significantly larger inductance values with large quality factors (Q).  Measurements of a 0.18 micron prototype show a maximum operating frequency 40% larger than published alternatives and a 12X improvement in quality factor.