Summary
In this review, different topologies of CMOS Colpitts oscillators including single‐ended and differential configurations are studied, and the main specifications of them are presented. The studied LC tank Colpitts oscillators operating at gigahertz frequencies are categorized in several main structures to have more insight into their comparison. Also, the main characteristics of the Colpitts voltage‐controlled oscillators (VCOs) are compared and analyzed according to their configurations and calculated results of their transconductances. Besides, the Colpitts quadrature voltage‐controlled oscillators (QVCOs) realized by the mentioned VCOs are studied and categorized. Also, the various coupling techniques adopted in each QVCO to generate output signals with 90° phase differences are highlighted.