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Abstract

After making a review of existing first-year laboratory work at Manchester Metropolitan University dealing with active filters, the authors describe an alternative set of first-year experiments which cover the three first-order filters whose transfer functions are controlled by a single time constant (first-order STC filters), namely, lowpass, highpass and allpass. The allpass filter can be regarded as an elementary parallel-path circuit with zero-order feedforward and this technique is extended to develop lowpass-to-highpass and highpass-to-lowpass converters which as well as allpass filters can be employed in the design of sinusoidal oscillators whose oscillation frequency can be adjusted using two similar grounded elements. Two approaches to the design of one such oscillator are given and experimental results are provided.

Keywords

active filters operational amplifiers sinusoidal oscillators

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References

Ganguly

U. S.

Ganguly

, ‘New canonic variable frequency RC harmonic oscillator with two similar sections’, Electron. Lett., 24 (1988), 1320–1321.

Vosper

J. V.

, Comment on ‘New canonic variable frequency RC harmonic oscillator with two similar sections’ and reply, Electron Lett., 25 (1989), 1374–1375.

Vosper

J. V.

Roitegui

, ‘Active-R three-phase oscillator operating at power line frequencies’, in Proc. European Conf. on Circuit Theory and Design, Stresa, 1999, Vol. 2, pp. 639–642.

Heima

M. M.

, ‘The design of active-R and active-RC oscillators’, PhD Thesis, Manchester Metropolitan University (1997).

Bhattacharyya

B. B.

Sundaramurthy

Swamy

M. N. S.

, ‘Systematic generation of canonic sinusoidal RC-active oscillators’, Proc. IEE, Part G, Electronic Circuits and Systems, 128(3) (1981), 114–126.

Boutin

, ‘Two new single op-amp RC bridge-T oscillator circuits’, Proc. IEE, Part G, Electronic Circuits and Systems, 130(5) (1983), 222–224.

Darkani

M. T.

Bhattacharyya

B. B.

, ‘Generation and design of canonic grounded-capacitor variable-frequency RC-active oscillators’, Proc. IEE, Part G, Electronic Circuits and Systems, 132(4) (1985), 153–160.

Malik

N. R.

, Electronic Circuits (Prentice-Hall, Englewood Cliffs, NJ, 1995), pp. 349–351.

Hambley

A. R.

, ‘Electronics, a top-down approach to computer-aided circuit design’, (Macmillan, New York, 1994), pp. 544–547.

10.

Vosper

J. V.

Heima

M. M.

, ‘Comparison of single- and dual- element frequency control in CCII-based active-RC oscillators using cascaded allpass sections’, in Proc. European Conf. on Circuit Theory and Design, Budapest, 1997, Vol. 1, pp. 88–93.