New Very-Low-Frequency Third-Order Quadrature Sinusoidal Oscillators Using CFOAs

Third‐order quadrature sinusoidal oscillators with fully uncoupled tuning laws using only two CFOAs and grounded capacitors

“…From Equations ( 2) and (3), it is noted that the circuits presented in Figure 1 provide fully decoupled control of FO and CO, that is, two resistors featuring in the expression for FO are not present in the expression of CO, and another two resistors that appear in the expression of CO do not feature in the expression for CO. Herein presented circuits, R 1 and † The genesis of these circuits is inspired by and is an extension of the methodology reported in Raj et al 23 R 2 , are used for maintaining the roots on jω-axis for sustained oscillations and the resistors R 3 and R 4 (which are not present in CO) are used to vary the frequency of the proposed TOQSOs.…”

“…A survey of previously reported VM TOQSOs based on three ABBs reveals that they suffer from one or more of the following drawbacks: (i) not employing all grounded capacitors, 8,9 (ii) nonavailability of independent control of CO and FO, 8,10,12,16,24 (iii) nonavailability of output voltages from low output impedance nodes, [9][10][11][12][13][14][15][16][17][18][19] and use of ABBs that are not yet commercially available. [13][14][15][16][17][18][19]24 From the various three-ABBs-based TOQSOs, only those of the previous studies [20][21][22][23] are based upon three CFOAs, which employ all the three grounded capacitors and also provide independent control of CO and FO. However, none of the three-ABBs-based TOQSOs known earlier possess all the features that are offered by the new TOQSOs presented in this paper.…”

“…Moreover, the circuits compared in Table 1 suffer from one or more of the following drawbacks: (i) employment of all ungrounded capacitors, [37][38][39][40] (ii) nonavailability of independent control of CO and FO both, [37][38][39][40] and (iii) nonavailability of both outputs from low output impedance nodes. [24][25][26][27][28][29][30][31][32][33][34] A careful inspection of all the previously known CFOA-based TOQSO circuits of [20][21][22][23] reveals that they require three CFOAs and 4/5 resistors but do not provide fully uncoupled control of CO and FO. The main objective of this paper is to report two new realizations of CFOA-based third-order quadrature sinusoidal oscillators providing fully uncoupled control of CO and FO while employing only two CFOAs, a canonic number of four resistors and a canonic number of only three capacitors all of which are grounded.…”

“…Thus, the novelty of the present manuscript lies in the introduction of two new circuits that can achieve all the above features with only two CFOAs, which has required at least three CFOAs to achieve the same features in the earlier works. [21][22][23] The organization of the manuscript is as follows: Section 2 presents the proposed TOQSO configurations and their mathematical analysis. Nonideal analysis has been carried out in Section 3, whereas Section 4 presents experimental results of the proposed configurations.…”

“…Of late, there also has been considerable research effort on third‐order oscillators since they are expected to provide high‐quality waveforms with low harmonic distortion 2,3 . Consequently, many authors have proposed third‐order quadrature oscillators using a variety of active building blocks (ABB) such as op‐amps, operational transconductance amplifiers (OTA), current differencing transconductance amplifiers (CDTA), multiple‐input second‐generation current conveyors (MOCCII), current differencing buffered amplifiers (CDBA), operational transresistance amplifiers (OTRA), voltage differencing buffered amplifiers (VDBA), differential voltage current conveyors (DVCC), differential difference current conveyors (DDCC), current controlled current conveyors (CCCII), voltage differencing transconductance amplifiers (VDTA), multiple‐output current controlled current conveyor transconductance amplifiers (MOCCCCTA), modified current following transconductance amplifiers (MCFTA), current‐controlled current conveyor transconductance amplifiers (CCCCTA), differential voltage current conveyor transconductance amplifiers (DVCCTA), voltage differencing inverting buffered amplifiers (VDIBA), fully differential second‐generation current conveyors (FDCCII), voltage differencing current conveyors (VDCC), and many more 4–51 …”