Linearly tunable quadrature oscillator derived from LC Colpitts structure using voltage differencing transconductance amplifier and adjustable current amplifier

摘要

The paper deals with an interesting oscillator solution derived from LC Colpitts circuit structure. Electronically controllable current gain of the current amplifier is utilized for driving of oscillation condition together with two transconductances in frame of voltage differencing transconductance amplifier for adjusting of frequency of oscillation. In the proposed structure these elements replace common bipolar transistor and metal coil. Designed circuit offers important advantages, i.e. absence of metal coil, quadrature outputs, amplitudes of generated signals independent of tuning process, linear electronic control of oscillation frequency (independent of oscillation condition). Implementation of circuit for amplitude stabilization and automatic control of oscillation condition for designed circuit is simple. These benefits are not available in classical LC Colpitts structures or in many well-known third-order oscillators. The theoretical conclusions are supported by experiments with behavioral representation employing commercially available devices and also by simulations using CMOS model.