More Enhanced Swing Colpitts Oscillators: A Circuit Analysis

Abstract

In this paper, we show that an additional inductor–capacitor–inductor filter can increase the oscillation amplitude of the enhanced swing Colpitts oscillator (ESCO), and call this topology the more enhanced swing Colpitts oscillator (mESCO). When it is connected with a rectifier, the DC–DC boost conversion ratio can be increased, especially for low-voltage sensor ICs or energy harvesting. This paper focuses on the electrical characteristics of mESCO. The oscillation frequency was modeled as a function of the circuit parameters of mESCO. The common gate voltage gain (ACG), defined by the ratio of the drain voltage amplitude to the source voltage amplitude of the switching MOSFET of mESCO, was also modeled under the assumption that all the circuit elements are ideal. The model was validated with a SPICE simulation. For ACG < 1.5, the model was in good agreement with the SPICE results within 10%. In addition, the drain voltage amplitude vda was modeled by assuming that the average transconductance of the MOSFET in a half cycle is null when the long-channel Shockley model is used. vda needs to be sufficiently high to have a large DC–DC boost conversion ratio. The model can predict the tendency that vda increases as ACG approaches unity. We found that the voltage difference of the drain voltage amplitude to the source voltage amplitude is a constant even when the circuit parameters, and thereby ACG are varied.