Low-power Gm-boosted complementary Colpitts LC-VCO/QVCO

Analysis and review of main characteristics of Colpitts oscillators

“…With the same concept, the oscillator shown in Figure 8B was reported in Cheng and Je 26 by employing an NMOS DS Colpitts core and PMOS cross‐connected pair. Similar to that explained in Hemmati et al 27 it can be shown that the minimum supply voltage required for this configuration to keep all transistors in saturation mode is decreased by an overdrive voltage ( V ov ) of Colpitts transistors ( M 1 and M 2 ) with respect to that of the oscillator shown in Figure 8A.…”

“…Some designs of QVCOs are based on the direct coupling of two identical VCOs without additional coupling components, and therefore, it does not add any noise sources and power dissipations to the core VCOs. In some of them, 16,26,27,42–44 the gate terminal of inherent transistors in each VCO is reused for directly coupling. In Cheng and Je, 26 a QVCO was proposed in which the gates of the Colpitts transistors from the first VCO are directly connected to the output nodes of the second VCO with the scheme of “in‐phase” and also the gates of the Colpitts transistors from the second VCO are connected to the output nodes of the first VCO in an antiphase manner.…”