The design of high-Q Sallen–Key biquads with unity-gain buffer amplifiers
✍ Scribed by Gaunholt, H.; Guldbrandsen, B.
- Publisher
- John Wiley and Sons
- Year
- 1997
- Tongue
- English
- Weight
- 244 KB
- Volume
- 25
- Category
- Article
- ISSN
- 0098-9886
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✦ Synopsis
In the design of active biquads with negative feedback, frequently referred to as Sallen-Key networks, the assumption of a low quality factor Q is recommended in order to keep the active sensitivities at a reasonably low value. In this paper it will be shown that it is possible to design and implement the Sallen-Key biquad even in the high-Q case with reasonable sensitivities. The method is based on the unity-gain version of the biquad, and since unity-gain buffer amplifiers are readily manufactured in integrated circuit technology, the results may be very useful in the fabrication of integrated analogue filters in voltage-mode as well as current-mode technology. As an example we choose the bandpass biquad, as biquads of this type often have to be designed with high Q-values. The results in the bandpass case may readily be transferred to the lowpass and highpass cases.