Active-filter tuned oscillator

An active-filter tuned oscillator is an active electronic circuit designed to produce a periodic signal. It consists of a bandpass filter and an active amplifier, such as an OP-AMP or a BJT. The oscillator is commonly tuned to a specific frequency by varying the reactant of the feedback path within the circuit. An example is the Colpitts oscillator.

Properties

An oscillator is any device or system that produces a periodic output. In a tuned oscillator, the period of the output may be controlled by altering the system's resonant frequency. In the case of a tunable electronic oscillator, this is most commonly achieved by altering the circuit's capacitance.

As with all oscillators, active-filter tuned oscillators adhere to the Barkhausen stability criterion, which states that the open-loop gain Aβ must be equal or greater than one, which means magnitude Aβ ≥ 1 and the phase shift around the loop is zero or an integer multiple of 2π: $\angle \beta A = 2 \pi n, n \in \{0, 1, 2,\dots\}\,.$ Whenever the criterion is satisfied the circuit starts to oscillate. To make the circuit oscillate at a certain frequency, a frequency selective circuit is made to satisfy the above criterion at a particular frequency. These circuits are called timing circuits of the oscillators.

References

External links

[https://web.archive.org/web/20131214055014/http://technologyinterface.nmsu.edu/fall98/electronics/grise/griseota.html Operational Transconductance Amplifiers (OTA) for synthesis of voltage-controlled active-filter tuned oscillators] by Dr. William R Grise
[https://web.archive.org/web/20140221170633/http://web.ics.purdue.edu/~ebaytok/projects/Oscillator.pdf El 303 Analog Integrated Circuits - Active Filter Design Oscillator] Design homework assignment
[http://www.edaboard.com/thread29954.html What is active filter tuned oscillator?] A forum thread on Edaboard.com
[https://web.archive.org/web/20140220225318/http://ahmadzadeh.iut.ac.ir/elec3/Oscillators.pdf Oscillators] by Edgar Sanchez-Sinencio
[http://www.cs.tut.fi/kurssit/TLT-8016/Chapter11.pdf Active Filters and Tuned Circuits]
[https://web.archive.org/web/20130419195704/http://faraday.elec.uow.edu.au/subjects/annual/ECTE313/week4_notes_4up.pdf ECTE 313 Electronics Part II, week 4] by Daniel Franklin
[http://sound.whsites.net/articles/active-filters.htm Active Filters - Characteristics, Topologies and Examples]
[http://homepages.wmich.edu/~miller/ECE3200/OscillatorCircuits.pdf Oscillator Circuits]
[http://www.site.uottawa.ca/~rhabash/ELG4139LN3Oscillators.pdf ELG4139: Oscillator Circuits]

Category:Electronic oscillators