The main working principle of voltage-controlled oscillator (VCO) circuits is based on self-generation of the output signal. The circuit components that enable self-oscillation can cause excess increase or decrease of the signal, resulting in amplitude noise. In the audio-frequency VCO, the standard capacitor or buffer can be used to reduce the noise. However, capacitor or buffer can modify the rise / fall time of the signal, which will lead to a change in the signal period. Additionally, these elements increase the circuit area. In this work, a new method for optimizing the audio-frequency VCO circuit is presented. The method is based on using, instead of an output operational amplifier, a simple circuit consisting of a Schmitt trigger and inverters and having smaller area compared to the operational amplifier. This makes it possible to get clear square signal. In addition, there is no need to use the resistors placed on the positive input of the operational amplifier. The folded cascode operational amplifier is used in the circuit. All other circuit components are the same as they were before the proposed method was used. It was demonstrated that the method under consideration lowers the output noise, allows the increase of the output characteristics linearity and the decrease of surface area of the audio-frequency VCO. It has been established that in the audio-frequency VCO designed in 32 nm technology, the noise is reduced by 30 %, the linearity error by 17 %, and the area by 28 %.
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Key words:
voltage-controlled oscillator, Schmitt trigger, inverter, operational amplifier, resistor, capacitor
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Published in:
CIRCUIT ENGINEERING AND DESIGN
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Bibliography link:
Babajanyan H. A., Khudaverdyan S. Kh. Optimization of the audiofrequency voltage-controlled oscillator. Proc. Univ. Electronics, 2024, vol. 29, no. 1, pp. 42–51. https://doi.org/10.24151/1561-5405-2024-29-1-42-51. – EDN: WFESBP.
Hayk A. Babajanyan
National Polytechnic University of Armenia (Armenia, 0009, Yerevan, Teryan st., 105); “Synopsys Armenia” CJSC (Armenia, 0026, Yerevan, Arshakunyats ave., 41)
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