Voltage Controlled Oscillators

Introduction A key circuit used in modern communication systems is the voltage controlled oscillator (VCO). The VCO's output is an AC waveform whose frequency is dependent upon the input voltage. In today's wireless communication systems, a greater maximum frequency range is required by VCOs. With respect to the digital phones that use these circuits, low power consumption, small size and low fabrication costs are important design factors. This report is an introduction to voltage controlled oscillators. Two styles of VCO (the LC oscillator and the RC relaxation oscillator) are described as well as the factors that influence their design and selection, the recent advances in the design of these circuits, and the next probable advance of these circuits in the state of the art.