Generation and design of sinusoidal oscillators using OTAS

The design of voltage-controlled oscillators (VCOs) using operational transconductance amplifiers (OTAs) is discussed. Several oscillator structures are proposed. They use only OTAs and capacitors (OTA-C) and are very appropriate for silicon monolithic implementations. The resulting oscillation frequencies are proportional to the transconductance of the OTA and this makes the reported structures well suited for building VCOs. Amplitude stabilization circuits using both automatic gain control (AGC) mechanisms and limitation schemes that are compatible with OTA-C oscillators are studied. Experimental results from breadboard prototypes are included, showing the good potential of OTA-based oscillators for high-frequency VCO operation.