Electronically tunable universal biquad using a single active component

The design of transconductance-mode multifunction biquad filter containing three input voltage nodes and single-output current node is proposed. Its circuit principle is emphasized on employing Voltage Differencing Current Conveyor (VDCC) to be an active building block. The proposed filter description uses three VDCCs co-working with two grounded capacitors and three grounded resistors. The synthesis of the proposed multifunction filter is based on avoidance of using multiple-output active elements to achieve commercially available integrated circuits for practical implementation. Additionally, without multiple-output active element, it can alleviate current tracking error from the current mirrors used in output ports. It also decreases the amounts of the transistors inside the active elements. The proposed multifunction filter offers all 5 filter functions, which are non-inverting Low-Pass (LP), non-inverting High-Pass (HP), non-inverting Band-Pass (BP), non-inverting Band-Reject (BR) and also non-inverting All-Pass (AP) functions from same circuit topology under different circuit condition for input signals. Furthermore, the natural frequency for all filtering responses is independently achieved from the bandwidth or the quality factor of the proposed filter. For cascade-able connectivity, the output current port indeed provides a high impedance. In addition, the magnitude of the output current for all filtering functions can be resistively adjusted. The consideration for non-ideal case of the presented multifunction filter is also analyzed. The simulation and experimental results of the presented transconductance multifunction biquad filter based on VDCC practically implemented by the commercially available ICs, LM13700 and AD844 can validate the theoretical anticipation.

A recently developed active element, namely Voltage Differencing Differential Voltage Current Conveyor (VD-DVCC), is employed in the design of electronically tunable mixed-mode universal filter. The filter provides low pass (LP), high pass (HP), band pass (BP), band reject (BR) and all pass (AP) responses in voltage-mode (VM), current-mode, trans-impedance-mode (TIM) and trans-admittance-mode (TAM). The filter employs two VD-DVCCs, three resistors and two capacitors. All the passive components employed are grounded. The attractive features of the filters include: (i) ability to operate in all four modes, (ii) use of grounded passive components, (iii) tunability of Q factor independent of pole frequency, (iv) high input impedance for VM and TIM mode, (v) high output impedance explicit current output for CM and TAM and (vi) no requirement for double/negative input signals (voltage/current) for response realization. The VD-DVCC is designed and validated in Cadence virtuoso using 0.18µm PDK at supply voltage of ±1V. The operation of filter is examined at 5.305 MHz frequency. The non-ideal gain and sensitivity analysis is also carried out to study the effect of process and components spread on the filter performance. The obtained results bear close resemblance with the theoretical findings.

In this paper, a new current-mode (CM) Kerwin-Huelsman-Newcomb ( KHN) biquad is proposed which is suitable for crossover networks. The proposed circuit employs three differential voltage current conveyors (DVCCs) as active elements together with two capacitors and four resistors as passive elements, which all are grounded. The circuit simultaneously provides the three basic filter functions, namely band pass (BP), high pass (HP) and low pass (LP) functions. TSPICE simulations are performed on employing CMOS Technology 2mum process and the performance simulation results is tested by comparing with the theoretical results of the filter.

Synthesis of biquad filters using two VD-DIBAs with independent control of quality factor and natural frequency

This paper proposes a current mode universal filter circuit, employing two active elements along with four grounded passive components only. The derived circuit realizes all five filtering responses, i.e., low pass (LP), band pass (BP), high pass (HP), band reject (BR) and all pass (AP), simultaneously from high-impedance ports along with the input being fed to low-impedance port, thus making it a fully cascadable filter. In addition, the designed circuit exhibits independent tunability of its quality factor. With the idea of making the proposed filter fully integrable, a resistor-less approach of the configuration has also been discussed. By making slight modifications in the filter configuration, a current mode single-resistance-controlled quadrature oscillator circuit has also been derived. The ideal, nonideal, sensitivity and parasitic analysis have been conducted for the designed configurations. The functionality of the proposed structures is verified by PSPICE simulations using 0.18[Formula: see text][Formula: see text]m CMOS technology. The designs have also been verified using PSPICE macro-model of the commercially available IC, i.e., OPA860.

The commercially available IC LT1228 is an interesting active device due to its advantage features, such as a fast transconductance amplifier, a wide bandwidth over a wide range of voltage gain, low total harmonic distortion (THD), high impedance differential input, etc. The single-input triple-output (SITO) voltage-mode (VM) multifunction biquadratic filters using ICs, LT1228s are introduced in this research. This circuit design provides the three-filtering functions, low-pass (LP), high-pass (HP), and band-pass (BP), without changing the circuit architecture. It comprises three LT1228s, four resistors, and two capacitors connected to the ground. The low impedance voltage output nodes are HP and BP responses. The quality factor (Q) and the pole frequency (ω0) can be electronically and orthogonally tuned by altering the third LT1228’s bias current (IB). The PSPICE simulation and the experiment are verified to describe the circuit operation.

This paper presents the second-order current-mode filter with 4 input currents and single output current. Five filter responses, namely High-pass (HP), Low-pass (LP), Band-pass (BP), Band-reject (BR) and All-pass (AP) filters are achieved. The pole frequency and quality factor are tuned by input bias current called electronic control. It has high output impedance which is able cascading in the current-mode filter and driving load without buffering devices. The filter uses only single active element namely current controlled current differencing transconductance amplifier (CCCDTA) and 2 grounded capacitors which is ideal for monolithic integrated circuit implementation. The filter was proved by Pspice simulation using BJT technology. The results are agreed with theoretical prediction.

This paper presents a systematic methodology for designing a voltage-mode multifunction biquad filter employing the commercially available active element, LT1228. The proposed topology adopts a three-input single-output (TISO) configuration. The circuit comprises a single LT1228, two capacitors, and three resistors, offering a highly compact design. The TISO biquad filter is capable of providing five fundamental filtering responses: low-pass (LP), band-pass (BP), high-pass (HP), band-reject (BR), and all-pass (AP) responses, within the same circuit architecture. Notably, these responses are achieved without the need for additional inverting amplifiers or reconfigurations of passive components. The parameters of the proposed filter, encompassing the natural (ω0 ) and quality factor (Q), are determined by electronic adjustment. Furthermore, we can adapt the proposed biquad filter to function as a current-controlled sinusoidal oscillator. The oscillation frequency is adjustable independently of the oscillation condition. We verified the performance and validity of the proposed circuits through PSpice simulations and experimental implementations in a laboratory setting. The proposed circuits hold immense significance for applications requiring precise signal generation and filtering, such as communication systems, test instrumentation, audio processing, automation and control systems.

A new circuit for realization of universal current-mode filter using current Follower Transconductance Amplifiers (CFTAs) is presented. The proposed circuit realizes current-mode low pass, high pass and band pass filter functions simultaneously with a single current source at the input. The band reject and all pass filters can also be obtained from the proposed circuit without any extra hardware. The proposed circuit employs three passive grounded elements and two CFTAs. Linear electronic control of natural frequency ω0 is available in the proposed circuit. The quality factor can be independently adjusted through grounded resistor. The proposed circuit employs two grounded capacitors and a grounded resistor along with two CFTAs. The grounded resistor can be replaced by an OTA based circuit for linear electronic control of quality factor Q0. The circuit exhibits low active and passive sensitivities for ω0 and Q0. Simulation results are obtained using PSPICE software which is in conformity with the theoretical findings.

In this paper a new realization of electronically tunable current-mode Active-C biquad filter is presented. In the proposed current-mode biquad filter, only a single modified current conveyor transconductance amplifier (MCCTA) as active building block and two grounded capacitors as passive elements are used. The proposed filter can realize three filtering functions namely, low pass (LP), band pass (BP) and high pass (HP), simultaneously. It is also capable of realizing band reject (BR) and all pass (AP) responses. The pole frequency and quality factor of the proposed circuit can be electronically and orthogonally tuned via only biasing currents of the MCCTA. The theoretical results of the filter are verified by P-SPICE simulation where standard 0.25um CMOS process parameters from TSMC were used.

In this paper two new voltage-mode (VM) universal filters employing three plus-type differential voltage current conveyors (DVCC+s) and grounded passive elements are presented. The first proposed filter is a single-input five-output (SIFO) circuit which can realize simultaneously all of the standard responses, i.e. low-pass (LP), band-pass (BP), high-pass (HP), all-pass (AP) and notch (NH) from the same configuration. The second proposed circuit is a three-input single-output (TISO) universal filter for realizing standard responses depending on the selection of the input signal from the same topology. Both of the proposed filters have the advantage of a high input impedance, which enables easy cascading to obtain higher order filters. The proposed filters are simulated using the SPICE program to verify the theoretical analysis.

To further extend the existing knowledge on voltage-mode universal biquadratic filter, in this paper, a new biquadratic filter circuit with single input and multiple outputs is proposed, employing three differential voltage current conveyors (DVCCs), three resistors, and two grounded capacitors. The proposed circuit realizes all the standard filter functions, that is, high-pass, band-pass, low-pass, notch, and all-pass filters simultaneously. The circuit enjoys the feature of high-input impedance, orthogonal control of resonance angular frequency (<svg style="vertical-align:-3.22281pt;width:16.862499px;" id="M1" height="11.0375" version="1.1" viewBox="0 0 16.862499 11.0375" width="16.862499" xmlns="http://www.w3.org/2000/svg"> <g transform="matrix(1.25,0,0,-1.25,0,11.0375)"> <g transform="translate(72,-63.17)"> <text transform="matrix(1,0,0,-1,-71.95,66.44)"> <tspan style="font-size: 12.50px; " x="0" y="0">𝜔</tspan> </text> <text transform="matrix(1,0,0,-1,-63.44,63.31)"> <tspan style="font-size: 8.75px; " x="0" y="0">o</tspan> </text> </g> </g> </svg>), and quality factor (<i >Q</i>) via grounded resistor and the use of grounded capacitors which is ideal for IC implementation.

This paper deals with application of novel active block called multiple-output current follower transconductance amplifier (MO-CFTA) in multiple-loop structure of current mode active filter. The well-known transconductance amplifier (OTA) is modified in such a way that single-input multiple-output active block is obtained. Using this device in the suggested network structure allows us to achieve low pass (LP), high pass (HP), band pass (BP) and band reject (BR) filter. The effects of the parasitic properties of the active devices as well as biquad sensitivities are briefly discussed. The possibility of electronic tuning of the main parameters of the individual filter configuration is verified.

In this paper, a voltage mode multifunction filter based on single voltage differencing differential difference amplifier (VDDDA) is presented. The proposed filter with three input voltages and single output voltage is constructed with single VDDDA, two capacitors and two resistors. Its quality factor can be adjusted without affecting natural frequency. Also, the natural frequency can be electronically tuned via adjusting of bias current. The filter can offer five output responses, high-pas (HP), band-pass (BP), band-reject (BR), low-pass (LP) and all-ass (AP) functions in the same circuit topology. The output response can be selected by choosing the suitable input voltage without the component matching condition and the requirement of additional double gain voltage amplifier. PSpice simulation results to confirm an operation of the proposed filter correspond to the theory.

A low power current controllable single-input three-output current-mode filter using MOS transistors only