Operational Transconductance Amplifier And Capacitor Research Articles

Oscillation-Based DFT for Second-Order Bandpass OTA-C Filters

This paper describes a design for testability technique for second-order bandpass operational transconductance amplifier and capacitor (OTA-C) filters using an oscillation-based test topology. The oscillation-based test structure is a vectorless output test strategy easily extendable to built-in self-test. The proposed methodology converts filter under test into a quadrature oscillator using very simple techniques and measures the output frequency. Using feedback loops with nonlinear block, the filter to oscillator conversion techniques easily convert the bandpass OTA-C filter into an oscillator. With a minimum number of extra components, the proposed scheme requires a negligible area overhead. The validity of the proposed method has been verified using comparison between faulty and fault-free simulation results of Tow-Thomas and KHN OTA-C filters. Simulation results in 0.25 $$\upmu $$ m CMOS technology show that the proposed oscillation-based test strategy for OTA-C filters is suitable for catastrophic and parametric faults testing and also effective in detecting single and multiple faults with high fault coverage.

Design of high-order elliptic filter from a versatile mode generic OTA-C structure

A new synthesis methodology for high-order versatile mode programmable Operational transconductance amplifier and capacitor (OTA-C) generic filter structure is proposed. The structure fulfills the three main criteria of high frequency operation i.e it uses (1) less number of components (2) only single ended input OTAs (3) only grounded capacitors. Any nth order transfer function can be realised from it. Elliptic filter is designed from the generic structure using optimisation technique to reduce the number of OTAs. SPICE simulation with BSIM level 53 model and 0.13 μm process confirms the theoretical analysis. Frequency response of third-order and fourth-order elliptic filter is shown as representative set of simulated result. Sensitivity and non-ideal effect of the designed filter are studied.

OTA-C Arbitrary-Phase-Shift Oscillators

This paper exhibits the generation of an operational transconductance amplifier and capacitor (OTA-C) arbitraryphase-shift sinusoidal oscillator (APSO) for an order n ≥ 3 for various advanced applications. A new nth-order quadrature oscillator (QO) is obtained via the algebraic quadrature manipulations of an oscillatory characteristic equation. Based on a phase shift transformation from a quadrature, an APSO is then generated by superposing OTAs with required +/- transconductance(s) in parallel with some grounded capacitor(s) on the QO. For eliminating nonideal and parasitic effects to improve phase accuracy, phase compensation schemes are proposed. A new native amplitude control exploiting the nonlinearity of all employed OTAs of the APSO is presented as well to lead to rather low THD and a lower variation of THD with respect to amplitude enlargement. A fourth-order APSO is demonstrated and simulated using Hspice with a 0.35-μm process for validation. In addition, its real application to a polyphase rectifier is improved. Finally, an experiment using LM13700s shows favorable potential of APSOs.

On the degradation of OTA-C--based CMOS low-power filter circuits for biomedical instrumentation

In this work, we propose a degraded transistor-based circuit degradation simulation method to investigate the degradation effect in complementary metal-oxide semiconductor (CMOS) biomedical devices. The method is demonstrated on an operational transconductance amplifier and capacitor (OTA-C)-based CMOS filter structure. First, we simulate the degradation of the symmetrical CMOS OTA by determining the degraded transistors in the structure. The simulation results are compared with the experimental results of our previous study. First- and second-order low-pass filter degradations are also simulated to demonstrate the accuracy of the proposed method. Finally, the degradation in the electroencephalogram band-pass filter and its effect on the diagnosis is discussed.

Performance comparison of high-order IFLF and LF linear phase lowpass OTA-C filters with and without gain boost

Design and performance comparison of high-order operational transconductance amplifier and capacitor (OTA-C) filters using leapfrog (LF) and inverse-follow-the-leader-feedback (IFLF) structures are investigated. The filters are designed for a 125 MHz seventh-order equiripple group delay lowpass characteristic with and without gain boost and simulated in 0.25 μm 2-V CMOS. A fully differential highly linear OTA with cross-coupled input pairs and regulated cascode output is used for the simulation. Simulated results show that while the IFLF OTA-C filter can achieve a higher gain boost, the LF OTA-C filter has better other performances.

Analytical Synthesis of Current-Mode High-Order Single-Ended-Input OTA and Equal-Capacitor Elliptic Filter Structures With the Minimum Number of Components

None of the previously reported third-order and fourth-order operational transconductance amplifier and capacitor (OTA-C) elliptic filter structures use the minimum number of active and passive components. After an innovative algebraic decomposition for a complicated transfer function, i.e., a new <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">analytical synthesis method</i> , a current-mode odd- <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> th-order and a current-mode even- <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> th-order OTA-C elliptic filter structure having the following advantages are presented: 1) all the OTAs have single-ended inputs; 2) all the capacitors are grounded; 3) the minimum active and passive components are used. An equal-capacitance-type structure is designed taking into account the difficulty of precisely fabricating capacitances in integrated circuits. Although the above three advantages lead to the lowest total parasitics and to the most precise output response, the small deviations (such as the 3.5159% error in f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p</sub> ) of the four parameters of the new third-order OTA-C elliptic filter can be drastically reduced (for example, to 0.1553% error in f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p</sub> ) by only slightly tuning the four transconductances, but fixing the ratio of the given three capacitances, and without adding any other active and passive components. H-spice high-pass and low-pass simulations with 0.35-mum process are provided to demonstrate the theoretical results.

Analytical Synthesis of Low-Sensitivity High-Order Voltage-Mode DDCC and FDCCII-Grounded &lt;emphasis&gt;R&lt;/emphasis&gt; and&lt;emphasis&gt; C&lt;/emphasis&gt; All-Pass Filter Structures

The difficulty of realizing the operations of addition and subtraction of a voltage-mode signal renders two special active elements, namely, differential difference current conveyors (DDCCs) and fully differential current conveyors (FDCCIIs), both of which have the ability to perform the operations of addition and subtraction, to become very important for voltage-mode analog filter design. Note that, for the design of operational transconductance amplifier and capacitor (OTA-C) filters, the recently reported analytical synthesis methods (ASMs) have been shown to be very effective for achieving simultaneously the three criteria, namely, all capacitors being grounded, the use of the minimum number of active and passive components, and the use of single-ended input OTAs. However, none of the ASMs uses DDCCs and FDCCIIs in the design of voltage-mode filters. In this paper, a method of realizing DDCC and FDCCII-based all-pass filter structures with either equal capacitances or equal conductances through a new ASM is presented. Only n current conveyors (the least number of active components), n grounded capacitors, and grounded resistors (the minimum number of passive components) are used for realizing an nth-order voltage-mode all-pass filter structure. Moreover, the new all-pass filter structure synthesized by the new ASM achieves very low individual as well as near-null group sensitivities just as in the case of the passive LC ladder filters, has very low power consumption, a low component spread for equal denominator conductance design, and a high input impedance which is attractive from the point of view of cascadability. Finally, H-Spice simulations, using 0.35-mum process and plusmn1.65-V supply voltages, are included and validate theoretical predictions.

Frequency-dependent harmonic-distortion analysis of a linearized cross-coupled CMOS OTA and its application to OTA-C filters

Recent progress of wide-band communication systems demands high-frequency circuits. Conventionally, the linearity of the operational transconductance amplifier and capacitor (OTA-C) has been analyzed using Taylor series expansion. Unfortunately, this approach does not predict the frequency-dependent linearity degradation. Thus, to properly design linearized OTAs, the frequency dependence of these coefficients must be determined. In this paper, we present a frequency-dependent harmonic-distortion analytical method applied to a linear-enhanced OTA. This OTA, which is suitable for high-frequency operation, uses three linearization techniques simultaneously: 1) attenuation through floating-gate MOS transistors; 2) source degeneration; and 3) polynomial cancellation techniques. By using the harmonic-distortion analysis, some properties on the performance of OTA are used to improve the performance of OTA-C based circuits at high frequencies. A 0.5-/spl mu/m CMOS OTA simulation and experimental results are shown to verify the harmonic-distortion analytical method.

Analytical synthesis of high-order single-ended-input OTA-grounded C all-pass and band-reject filter structures

The synthesis method based on the analytical solution of a single nth-order filter transfer function and the generation of n+1 simple and realizable transfer functions implemented using lossless integrators and one additional constraint is applied to facilitate the development of new voltage-mode high-order operational transconductance amplifiers and capacitors (OTA-C) all-pass and band-reject filters. The presented nth-order all-pass and band-reject filters contain n+2, i.e., at least n fewer OTAs and enjoy lower component spread than the recently published filter structures in addition to achieving three criteria: all single-ended-input OTAs, all grounded capacitors, and the least number of component counts, simultaneously. Furthermore, two different types of the synthesized filter structures, equal capacitance and equal transconductance, are suggested for easier IC manufacture and simpler biasing architecture, respectively. H-Spice simulations, using 0.25-mum process and plusmn1.25-V supply voltages, validate theoretical predictions

PERFORMANCE ANALYSIS AND COMPARISON OF MULTIPLE LOOP FEEDBACK OTA-C FILTERS

This paper is concerned with performance analysis and comparison of multiple loop feedback (MLF) operational transconductance amplifier and capacitor (OTA-C) filters. General formulas for analysis of sensitivity, maximum input signal and noise based on the matrix method of MLF OTA-C filters are derived for canonical and noncanonical all-pole and finite transmission zero architectures. These formulas can be readily used for performance evaluation of any MLF filters. For illustrating the use of the formulas and comparison of different structures, the performances of inverse-follow-the-leader-feedback (IFLF), leapfrog (LF), and cascade MLF OTA-C filters are simulated ideally and at CMOS transistor level, realizing the same lowpass Butterworth characteristic and using the same OTA. Results show that the LF filter has the lowest passband magnitude sensitivity, highest maximum input signal, and best magnitude response, whilst the cascade filter has the lowest group delay sensitivity, best noise performance and best group delay response. Results also reveal that the IFLF filter has better passband magnitude sensitivity than the cascade filter and better passband group delay sensitivity than the LF filter, but it is the worst in other performances.

Microprocessor-controlled OTA-C lowpass and bandpass filters

A realization scheme is given of a high input impedance active biquadratic filter circuit which simultaneously gives lowpass and bandpass responses using operational transconductance amplifiers and capacitors (OTA-C). The circuit basically uses two rogrammable integrators (PIs) and an additional OTA. Microprocessor control of the ole frequency (ω0) and ole-Q (Q) of the filter is achieved by employing a Motorola 68000 microprocessor and eripheral devices. Electronic control of the filter arameters is also available through the OTAs bias currents. The circuit has excellent sensitivity erformance and is suitable for implementation in CMOS-technology. The circuit is attractive for applications in music synthesis, speech synthesis, automatic control, etc. where electronic/digital control of the filter arameters is required. Experimental results on the discrete version of the circuit are included