Multiple-input single-output universal biquad filter using single output operational transconductance amplifiers

Versatile Tunable Voltage-Mode Biquadratic Filter and Its Application in Quadrature Oscillator

“…The recently reported electronically tunable OTA-based multiple-input single-output voltage-mode universal biquadratic filters have been proposed [19,20] that can realize all five standard filtering responses with the following four attractive advantages: (i) orthogonal controllability of the parameters resonance angular frequency (ω o ) and quality factor (Q), (ii) possession high impedance at input terminal, (iii) all grounded passive components, and (iv) no need to employ inverting-type input voltage signals. The circuit [19] also permits resistorless realization along with two grounded capacitors but the parameters ω o and Q cannot be independently controllable. Although the circuit [20] permits independent of the parameters ω o and Q, it cannot achieve resistorless structure.…”

“…Although the circuit [20] permits independent of the parameters ω o and Q, it cannot achieve resistorless structure. Both the circuits in [19,20] need to use six OTAs as the active devices and cannot simultaneously realize lowpass, bandpass, and bandreject filters from the same configuration.…”

“…The proposed circuit enjoys the following advantages: (i) the employment of only five single-ended output OTAs, (ii) the employment of only two grounded capacitors, and thus can absorb equivalent shunt capacitive parasitics, (iii) capability to realize IBP/BP, LP/ILP and BR/IBR filtering responses simultaneously with single-input three-output, (iv) independent control of the LP, ILP, BP and IBP gains simultaneously without affecting the parameters of ω o and Q, (v) realization of all five standard filtering functions with five-input single-output by appropriate selecting different five input voltage signals, (vi) possession high-input impedance, (vii) no need to employ inverting-type input voltage signals, (viii) independent electronic adjustment of the parameters ω o and Q, (ix) easy transformed into a quadrature oscillator, and (x) low active and passive sensitivity performances. Table 1 compares the proposed filter with recently reported voltage-mode OTA-based biquadratic filters [19,20]. Unlike the reported voltage-mode OTA-based biquadratic filters in [19,20], the attractive feature of the proposed filter is that it employs only five single-ended OTAs and two grounded capacitors for realizing voltage-mode biquadratic filter and capability to realize IBP/BP, LP/ILP and BR/IBR filtering responses simultaneously with single-input three-output.…”

“…Table 1 compares the proposed filter with recently reported voltage-mode OTA-based biquadratic filters [19,20]. Unlike the reported voltage-mode OTA-based biquadratic filters in [19,20], the attractive feature of the proposed filter is that it employs only five single-ended OTAs and two grounded capacitors for realizing voltage-mode biquadratic filter and capability to realize IBP/BP, LP/ILP and BR/IBR filtering responses simultaneously with single-input three-output. Moreover, the LP, ILP, BP and IBP gains can be independently controlled simultaneously without affecting the parameters of ω o and Q.…”

0.5 V Fully Differential Universal Filter Based on Multiple Input OTAs

“…The designs of second order or biquad filters are receiving a lot of attention, especially the universal biquad filter which provides all five filtering responses, low-pass (LP), band-pass (BP), high-pass (HP), all-pass (AP), and band-stop (BS) functions into single circuit scheme [1]. The universal biquad filter can be used in areas such as in touchtone telephone tone decoder, FM stereo demodulation, and audio crossover network circuit [1][2][3]. The design of analog active filters employing the single-ended active function blocks has been continuously presented in the open literature [4][5][6][7][8].…”