Inductors and Transformers: Enabling the Gigahertz Silicon IC Revolution

Today we are all accustomed to miniature wireless devices embedded in our mobile phones, laptops, printers, thermostats, and even watches and glasses! This wireless revolution has its roots in technology scaling, in particular smaller and faster transistors allowing higher speed operation, into the gigahertz regime where antennas are small and plenty of bandwidth exists for high speed communication. Along the way we can identify many key ideas, process technology advancements, and other innovations that took us from brick sized mobile phones to today´s sleek devices. One key idea along the way was the realization that on-chip inductors and transformers were an enabling technology to make this happen. In their seminal paper in 1990 [1], Prof. Meyer and his graduate student Nhat Nguyen were the first to have this key insight, and they demonstrated that inductors on the silicon substrate were viable for the realization of LC tanks and filters, low phase noise VCOs, and other key building blocks operating in the gigahertz frequency range (See Fig. 1) [2][3].