Two new multiple-mode (including voltage, current, transconductance, and transresistance modes) OTA-C universal biquad filters are proposed. The first proposed circuit uses only four operational transconductance amplifiers (OTAs) and two grounded capacitors. The second proposed circuit uses five OTAs and two grounded capacitors. Both the proposed circuits can realize voltage, current, transconductance, and transresistance mode universal filtering responses (low-pass, high-pass, band-pass, notch, and all-pass) from the same topology. The first proposed circuit uses the least number of components. This represents an attractive feature from a chip area and power consumption point of view. The second proposed circuit has no need of extra inverting and non-inverting amplifiers for special input signals. Moreover, both the proposed biquads still have (i) the employment of two grounded capacitors, (ii) cascadable connection of the former voltage-mode stage and the latter current-mode stage, and (iii) low sensitivity performance. H-SPICE simulation results confirm the theoretical analysis.

Multiple-Mode OTA-C Universal Biquad Filters

In this paper, new biquad filter configuration using a recently introduced active element, namely Voltage Differencing Buffered Amplifier (VDBA), is proposed. This block has high impedance input terminals and low impedance output terminal, providing advantages at voltage mode circuits. Besides, VDBA has a trans- conductance gain, thus the proposed circuits can be employed without using any external resistors. Two new voltage-mode biquad filter configurations are presented for VDBA application. Each proposed filter employs two active elements and two or three passive components. Filters, having three inputs and single output, can realize voltage- mode low-pass, band-pass, high-pass, band-stop, and all- pass filters. The biquad filters have low output impedances that is necessary for cascadability for voltage mode circuits, and no critical component matching conditions are required. For the second biquad, quality factor can be adjusted via resistor independently of the natural frequency. Simulation results are given too, confirming the theoretical analysis. The proposed biquad filters are simulated using TSMC CMOS 0.35 µm technology. LTSPICE simulations of the proposed circuits give results that agree well with the theoretical analysis.

New CMOS Realization of Voltage Differencing Buffered Amplifier and Its Biquad Filter Applications

This paper presents a new current-mode single input multi output (SIMO) type biquad employing one voltage differencing transconductance amplifier (VDTA), two grounded capacitors and a single grounded resistor. The configuration realizes all basic filter functions (i.e. Low Pass (LP), High Pass (HP), Band Pass (BP), Notch (BR) and All Pass (AP)). The natural frequency (ω0) and bandwidth (BW) are independently tunable. The workability of proposed configuration has been verified using SPICE simulation with TSMC CMOS 0.18 μm process parameters.

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Universal Current-Mode Biquad Filter Using a VDTA

The transconductance and the transresistance modes might act as the bridge transferring from voltage-mode to current-mode and vice versa, respectively. A novel mixed-mode (including voltage, current, transconductance, and transresistance modes) biquad filter with one input and seven outputs or two inputs and eight outputs is presented. The proposed filter structure only uses a single fully differential current conveyor (FDCCII), three resistors and two grounded capacitors, which are the least components necessary for realizing voltage, current, transresistance modes all five standard filter functions and transconductance-mode band-pass, high-pass filter functions from eight output terminals. Moreover, the new mixed-mode biquad filter still enjoys (i) the employment of two grounded capacitors (attractive for absorbing shunt parasitic capacitance and ideal for IC implementation), (ii) orthogonal control of ω 0 and Q (easy for tunability), and (iii) high output impedance of three current outputs (good for cascadability). H-Spice simulation results verify the theoretical analysis.

Single FDCCII-based mixed-mode biquad filter with eight outputs

This study presents an electronically tunable low-voltage mixed-mode universal biquad filter. The proposed filter employs only three current controlled current conveyor trans-conductance amplifiers (CCCCTAs) and two grounded capacitors. The proposed filter can realise low pass, band pass and high pass responses in all the four possible modes, that is, voltage-mode, current-mode, trans-admittance-mode and trans-impedance-mode from the same configuration. The filter can also realise regular notch, low-pass notch, high-pass notch and all pass responses in current and trans-admittance-mode, with interconnection of relevant output currents. The filter parameters namely pole frequency, quality factor, bandwidth and filter gains can be tuned electronically. Moreover, the circuit parameters such as pole frequency and quality factor can be simultaneously current controlled without affecting bandwidth. Effects of non-idealities and parasitic are also discussed. The circuit possesses low active and passive sensitivity and can be operated at low power supply (±1 V). The validity of the proposed filter is verified through computer simulations using PSPICE, the industry standard tool. Possible experimental setup for CCCCTA using commercial available integrated circuits is further discussed.

Electronically tunable low-voltage mixed-mode universal biquad filter

The transconductance and the transresistance modes might act as the bridge transferring from voltage mode to current mode and vice versa, respectively. This paper presents a new mixed-mode (including voltage, current, transconductance, and transresistance modes) high-order universal filter structure using n+1 differential difference current conveyors (DDCCs), n grounded capacitors and n+2 grounded resistors, which are the minimum components necessary for realising an nth-order mixed-mode universal filtering response (low-pass, high-pass, band-pass, band-reject, and all-pass) from the same topology. Moreover, the proposed circuit simultaneously achieves nearly all of the main advantages. H-Spice simulation results confirm the theory.

High-order DDCC-based general mixed-mode universal filter

The transconductance and the transresistance modes might act as the bridge transferring from voltage mode to current mode and vice versa, respectively. This brief presents a universal mixed-mode high-order OTA-C filter structure using n + 1 single-output OTAs, one multi-output OTA, and n grounded capacitors. The proposed circuit can realize n th-order mixed-mode (including voltage, current, transconductance, and transresistance modes) universal filtering responses (lowpass, highpass, bandpass, bandreject, and allpass) from the same topology. The proposed circuit uses the least number of components count. This represents the attractive feature from chip area, and power consumption point of view. H-spice simulation results confirm the theoretical analysis.

High-order mixed-mode OTA-C universal filter

This paper presents an independently tunable mixed-mode (including voltage, current, transadmittance, and transimpedance modes, i.e. four modes) universal biquad filter using one fully differential current conveyor (FDCCII), one differential difference current conveyor (DDCC), two grounded capacitors, four grounded resistors, and two floating resistors, which can realize all four modes five universal filtering responses (lowpass, highpass, bandpass, notch, and allpass). The proposed biquad filter has versatile input/output functions which not only realize all four modes five universal filtering functions in single-input multiple-voltage/current-output (SIMO) type but also provide all of them in multiple-input single-voltage/current-output (MISO) type without changing the filter topology. The proposed circuit permits both independent tunability (for ω 0 and ω 0 / Q ) and orthogonal controllability (for ω 0 and Q ) by adjusting grounded resistors without control factors matching conditions. No floating capacitors are used, and all the active and passive sensitivities are low. Moreover, in some modes, the proposed circuit still maintains the following advantages for five universal filtering responses: (i) cascadable feature, (ii) no component-value constraints, and (iii) no need of extra inverting or non-inverting amplifiers. H-spice simulations with TSMC 0.18 μm 1P6 M CMOS process technology and experimental results validate theoretical predictions.

Chen-Nong Lee

Papers

Multiple-Mode OTA-C Universal Biquad Filters

Single FDCCII-based mixed-mode biquad filter with eight outputs

High-order DDCC-based general mixed-mode universal filter

High-order mixed-mode OTA-C universal filter

Independently tunable mixed-mode universal biquad filter with versatile input/output functions