An Approach to CFOA-based Second-Order Universal Filters

The paper presents a new second-order single input multiple output (SIMO) type current mode (CM) universal filter. The proposed circuit uses two dual-X second generation multi-output current conveyors (DX-MOCCII), two grounded capacitors and three grounded resistors. The circuit configuration realizes low-pass filter (LPF), high-pass filter (HPF), band-pass filter (BPF), notch filter (NF) and all-pass filter (APF) responses simultaneously at different output terminals. The new circuit enjoys the features of low input impedance and high output impedance, which is desirable and useful for cascadability in CM circuits. For realizing the universal filter responses, the proposed circuit configuration does not require matching constraint of passive components and both active and passive sensitivities are found low. In addition, the extension of the proposed circuit as a resistorless universal filter has also been presented. As an application of the proposed filter, inverting band pass output is connected to a negative unity gain current follower in a close loop to design voltage and CM multiphase sinusoidal oscillators (MSOs). Comparison of the proposed configuration with available literature is given. The PSPICE simulation of the filter and its application as MSO are performed to verify the agreement with the theoretical proposition.

In this paper, a new voltage-mode (VM) multifunction filter including only two grounded capacitors, three resistors, and two current feedback operational amplifiers is introduced. This filter with one high input impedance and two low output impedances can simultaneously provide band-pass filter (BPF) and low-pass filter (LPF) responses with an adjustable gain. A universal VM filter topology with three inputs and one output generating high-pass filter (HPF), BPF, LPF, notch filter, and all-pass filter (APF) responses is obtained from the multifunction one. It has the same number of active and passive elements as the multifunction and a low output impedance. Sensitivities of both introduced filters are low enough. However, the APF of the introduced universal filter has a passive element-matching problem. As an example, parasitic impedance effects are considered for the LPF of the universal filter, while non-ideal gain analyses are given for the HPF. To see how the introduced universal filter works, countless simulations are performed through the SPICE (Simulation Program with Integrated Circuit Emphasis) program in which 0.13 [Formula: see text]m IBM CMOS technology parameters are utilized. DC supply voltages are selected as ± 0.9 V. Also, several experiments using commercially available AD844s with ± 10 V supply voltages are carried out to see the performance.

This paper puts forward a new operational floating current conveyor (OFCC)-based current mode (CM) single input multiple output (SIMO) filter configuration which uses two grounded capacitors, three grounded resistors and three OFCCs. The attractive features of the proposed filter are—use of grounded passive elements; availability of low pass, band pass, high pass and notch filter responses simultaneously at high output impedance; and independent adjustment of filter parameters. These features make the proposed filter suitable from fabrication viewpoint and allow easy cascading. Effect of nonidealities on proposed filter response is also examined. A CM shadow filter is also built by introducing an OFCC-based amplifier and connecting it in a feedback loop of the proposed SIMO filter. This configuration allows adjustment of filter parameters through gain of amplifier. MOS-based implementation of grounded resistors is incorporated to facilitate electronic tuning of filter parameters. The operation of the proposed filters is verified through SPICE simulations using $$0.5\,\upmu \hbox {m}$$ technology model parameters from MOSIS (AGILENT). Proposed CM SIMO filter is prototyped using commercially available IC AD844, and experimental response is found to be in close agreement with theoretical ones.

In this study, a new simulated grounded inductor (SGI) is developed. It has a simple structure because it employs two-terminal active devices (TTADs). Moreover, it has a minimum number of passive elements, considering the TTAD-based configurations. However, there is a single passive element-matching constraint for two resistors. Derived from the developed SGI, a second-order voltage-mode universal filter application is given. With proper connection of inputs, it yields band-pass (BP), high-pass (HP), low-pass (LP), all-pass (AP), and notch filter (NF) responses. The performance of the developed circuits is verified through the SPICE simulation program. Additionally, an experimental test result is given for the developed SGI. Cite this article as: F. Yücel, “A new simulated grounded inductor with two-terminal active devices,” Electrica., 22(2), 278-286, 2022.

Fully integrable mixed-mode universal biquad with specific application of the CFOA

A novel electronically tunable mixed-mode universal biquad by using four single-output and one dual-output-operational transconductance amplifiers, two grounded capacitors is proposed. The proposed circuit has ability to realize voltage, current, transconductance, and transresistance mode, and can the following advantageous features: (i) realization of low-pass, band-pass, high-pass, notch, and all-pass filter responses from the same configuration, (ii) employment of only grounded capacitors ideal for integrated circuit implementation, (iii) orthogonal controlling of ? o and Q for easily electronic tunability, and (iv) low active and passive sensitivity performance. Finally, to verify our architecture, we have designed this analog filter chip with TSMC 0.35-μm 2P4M CMOS technology. This chip operates to 1 MHz and consumes 30.95 mW. The chip area of the analog filter is about 0.823 mm2.

In this paper, a new active current-mode (CM) minimal component, cascaded current differencing unit (CCDU) and a CM nth-order filter based on the CCDU have been presented. The proposed CCDU simplifies the design of the CM nth-order filter circuit considerably. The proposed nth-order circuit, which adopts only an active component and n grounded capacitors, can simultaneously realize low-pass (LP), band-pass (BP) and high-pass (HP) filter responses. It enjoys the simple configuration and is suitable for integrated circuit (IC) fabrication. PSPICE simulations and experimental tests for CM third-order filter based on this structure have also been conducted and the results have good agreement with the theoretical analysis.

This paper presents formulations for time-based first-order and second-order high-pass, shelf, and notch filters. These formulations are an extension to the existing literature where low-pass filters are already developed using a multiphase controlled oscillator in conjunction with a phase detector and charge pump. The presented high-pass filter expands the circuit by introducing a current-controlled delay line (CCDL) that provides a direct path from input to output. By combining the high-pass filter with the low-pass filter, we show that shelf and notch filters can be obtained without an increase in circuit complexity compared to the high-pass filter. The results show good matching between the ideal small signal and the simulated time-based large signal frequency response. The simulated of total harmonic distortion for the filters shows an increase in distortion due to the nonlinearities introduced by the CCDL for the high-pass, notch, and shelf filter compared to the existing low-pass filter. The derivation of the new filter types allows the creation of complex high-order time-based filters by combining multiple first- or second-order filters.

A new voltage mode, carbon nanotube field-effect transistor (CNTFET) based multiple input single output active only biquadratic filter (AOBF), is presented. The proposed AOBF employs simple and compact single ended transconductance elements, voltage-controlled resistor (VCR) and varactor. The proposed AOBF provides band-pass filter, band-reject filter, all-pass filter, high-pass filter and low-pass filter responses, just by selecting the appropriate inputs. The AOBF operates at low-voltage supply of 0.7 V and suitable for integration due to absence of any external passive component. The realized AOBF also enjoys the attractive features of orthogonal voltage-controlled tuning of its pole-Q and pole-ωo, low incremental sensitivity performance and suitability for multi-GHz frequency applications. The pole-Q of the filter is controlled through CNTFET-based VCR while the pole-ωo is controlled through the CNTFET-based varactor. To validate the performance, HSPICE simulation on the designed AOBF was carried out using Stanford CNTFET model at 16 nm technology node. The simulation results thus obtained, justify the theory proposed.

A new realization of an analog circuit topology realizing current-mode (CM) first-order low-pass (LP), high-pass (HP), and all-pass (AP) filter responses using current backward transconductance amplifier (CBTA) and single grounded capacitor is introduced. The investigated resistorless CBTA-C AP filter provides electronic tunability of the pole frequency in range from 763 kHz to 17.6 MHz and its maximum power dissipation is 828 μW. Non-ideal analysis, study of parasitic effects, output/ input noise variations, and Monte Carlo analyses results are given. The theory is verified by SPICE simulations using a new low-voltage structure of CBTA via PTM 0.09 μm level-7 CMOS process BSIM3v3 parameters with ±0.45 V supply voltages.

In this study, a novel DDCC-based two-integrator-loop universal active-C biquad with a companding process scheme is proposed. The proposed filter employs some processing blocks such as integrators and summing blocks. The use of the block diagram design procedure is attractive and systematic. The state space synthesis technique is utilized for the topology of the integrator design. Several advantages of the proposed filter are briefly expressed as: simultaneously realizing five second-order filter functions such as low-pass, high-pass, band-pass, all-pass and notch filter responses; offering resistorless realization; dissipating low power; having electronic tunability feature of its pole frequency and quality factor orthogonally; not suffering from disadvantages of the passive element matching problems. Some simulation results including frequency and time domain analysis results by using the PSpice program are carried out to confirm the theoretical ones. All the obtained simulation results are discussed.

A new design approach of current-mode ( CM) filters is presented. The proposed method is based on simulating the RLC ladder networks using coupled-biquad structures. The loop and branch currents are used as variables to generate coupled-biquad transfer functions that are realized by CM circuits implementing OTAs with multiple outputs. Design of low-pass, band-pass, and high-pass filters with all-pole and elliptic responses are presented. The resulting CM structures only use grounded capacitors making it suitable for VLSI. To illustrate this approach, the implementation of a OTA-based 5th-order all-pole low-pass current-mode filter is designed and simulated in HSPICE.

A voltage-mode fully cascadable biquad with three CFOAs and grounded capacitors

In this paper, a current-mode circuit for realizing high-order low-pass (LP) and high-pass (HP) filter responses is presented. The proposed circuit uses dual output second-generation current controlled conveyors (DO-CCCII) and only grounded capacitor. The coefficients of the filter transfer functions (TFs) can be tuned electronically via external biasing currents of the active elements. Also, LP and HP filters are connected in cascade to obtain a band-pass (BP) filter. Simulations are performed for fourth-order and eighth-order filter responses to illustrate the frequency domain performance of the circuit.

Chapter 22 - High Speed Filter Design