Improved design of a multifeedback bandpass filter

✍ Scribed by Mario Biey; Amedeo Premoli

• Publisher: John Wiley and Sons
• Year: 1975
• Tongue: English
• Weight: 487 KB
• Volume: 3
• Category: Article
• ISSN: 0098-9886
• DOI: 10.1002/cta.4490030210

✦ Synopsis

Abstract

The multifeedback second‐order RC active filter is of considerable interest and has been studied extensively. Nevertheless, its behaviour has been in general analysed without making allowance for the non‐ideal characteristics of the embedded operational amplifier (OA).

This paper presents some formulas that can be used for improving the design of such a filter. They were derived on the basis of an OA model that takes into account both input and output resistances, unity‐gain frequency, and dc‐gain. They make use of algorithms characterized by a relative simplicity and quite a good approximation. Their application makes the filter easy to tune and usable for high frequencies, while at the same time the dependence of the Q‐value on temperature variations in the operational amplifier is minimized.

Two universal graphs are given in the text. They simplify the use of the new formulas in obtaining the analysis and the synthesis of the multifeedback second order filter. Experimental results that check the validity of the proposed formulas are presented.