Selectivity enhancement of certain low-sensitivity RC active networks †

Abstract

A technique is described for improving the sclecuvir.v of a low-sensitivity multi. loop negative feedback fictive network, which uses one operational amplifier. Voltage amplifiers with positive finite gain arc introduced inside the various loops of the network. This simplifies quite considerably the network function and improves the selecbivit.y for 11 given range of clement values ,vhilc not affecting the low sensitivity of t.he network. Also, additional low impedance out.put.a are available which for a particular input make the network suitable for the simultaneous realization of more than one function (with common poles but different zeros). Second and third-order networks are examined in detail and experimental results arc given from their usc in t.he realization of a band-pass and a low-pass filter.

A 1V 8th-order 250MHz current-mode butterworth lowpass filter

“…A single amplifier biquad (SAB) is the simplest way to realize a biquadratic transfer function (biquad) [19]. A large number of two-opamp biquads were obtained for the enhancement of the Q factor and reduction of the sensitivity of certain SABs [20][21][22][23]. The use of three opamps to realize second-order filter functions leads to multiple-output biquads with the additional advantage of versatility in that w0 , Q, and the filter gain can be independently adjusted [24][25][26][27][28].…”