Abstract
The present article is related to the recently published paper given in (Abuelma’atti and Khalifa, Analog Integr Circuits Signal Process, 73:989–992, 2012), which depicts the possible relation between the modified Wien-bridge circuit used by the authors of references (Singh, Analog Integr Circuits Signal Process 48:251–255, 2006; Singh, Analog Integr Circuits Signal Process, 50:127–132, 2007; Singh, Analog Integr Circuits Signal Process, 62:327–332, 2010; Wangenheim, Analog Integr Circuits Signal Process, 66:139–141, 2011; Martinez-Garcia et al., Analog Integr Circuits Signal Process, 70:443–449, 2012), and the comparator-based relaxation oscillator. In particular, in the referenced Mixed Signal Letter (Abuelma’atti and Khalifa, Analog Integr Circuits Signal Process, 73:989–992, 2012), the authors assert that the modified Wien-bridge oscillator circuit under discussion, used previously in the aforementioned referenced articles, can behave as a sinusoidal oscillator only at relatively high frequencies when the operational amplifier can be considered non-ideal. In addition, at relatively low frequencies, when the operational amplifier can be considered ideal, the same circuit would behave as a relaxation oscillator with a square wave output rather than a sinusoidal output. However, this paper reveals that this assertion is not strictly correct, because in both cases (in low and high frequencies), the generated waveform at the circuit output is a sinusoidal signal, with the possibility of be cut out, depending on proper circuit dimensioning (according to the oscillation criterion) as well as the oscillation frequency and the properties of the amplifier (slew rate, and frequency response).
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References
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Acknowledgments
The author would like to thank Professor Lutz v. Wangenheim for enriching and helpful discussions. This work has been partially funded by project TEC2010-15765/MIC from the Spanish MICINN funds.
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Martínez-García, H. On modified Wien-bridge oscillator and astable oscillator. Analog Integr Circ Sig Process 75, 179–194 (2013). https://doi.org/10.1007/s10470-013-0032-z
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DOI: https://doi.org/10.1007/s10470-013-0032-z