Single-CFA first-order allpass filter

Abstract

A simple first order allpass filter (APF) realization scheme with single current feedback amplifier (CFA) is presented; the phase-select component Y (= sC) is grounded. Analysis indicates that effects of imperfect port mismatch ratio of the CFA are quite insignificant. However the device parasitic capacitors introduce certain phase error at relatively higher frequencies. This simple circuit may be extended to second order APF design, if desired with Y as a shunt −LC resonator; L being a lossless inductor simulated by a DVCCTA element. Literature study on recent first order APF indicates that these are based on active elements that are based essentially on assorted conjoined versions of two types of devices.

A linear electronically tunable sinusoid oscillator

“…These port transfer co-efficients are ideally unity, but exhibit single-pole rolloff feature as α≈α o /(sη i +1), β≈ β o /(sη v +1) and δ≈δ o /(sη z +1);the corner frequencies appear at several MHz-range [28,29]. For f < f i,v,z , some error terms (ε i,v,o <<1) are postulated [1,18]…”

Design of Voltage Mode Electronically Tunable First Order All Pass Filter in ±0.7 V 16 nm CNFET Technology

“…It is used for design of multiphase oscillators, phase-equalizers and high-quality-factor frequency-selective circuits. Several first order voltage mode (VM) single-ended (SE) APF circuit realizations have been reported in technical literature [1][2][3][4][5][6][7][8]. These APF circuits use a variety of efficient active-building-blocks (ABBs).…”