Simple and low-cost voltage-controlled oscillator

This paper presents a simple circuit technique based on commercially available devices to implement voltage-controlled oscillator (VCO) with two high-impedance input terminals. By suitably setting two input signals, a linear frequency-voltage relation of the proposed VCO can be either positive or negative slope in the same scheme without any adapting configuration. The oscillation gain can be easily adjusted through the variation of a single resistor. Compared to the previous circuit based on similar technique, the proposed VCO offers significant improvement in circuit configuration. Its benefits are simpler structure, lower components, and lower costs. Experimental results showing performances of the proposed VCO are in close agreement with expected values.