dual-X Current Conveyor Transconductance Amplifier Research Articles

Fully Electronically Tunable and Easily Cascadable Square/Triangular Wave Generator with Duty Cycle Adjustment

A novel multiple-output dual-X current conveyor transconductance amplifier with buffer-based square/triangular wave generator is introduced in the paper. The proposed generator provides square wave in current mode and triangular wave in voltage mode. Outputs as square and triangular waves are available from terminals with appropriate impedance levels thereby making the proposed generator circuit easily cascadable in both current and voltage modes. The oscillation frequency and amplitude of output square wave are electronically and independently controllable. One more interesting feature of the proposed generator circuit is the adjustable duty cycle. The proposed circuit of square/triangular wave generator is verified through the HSPICE simulation results carried using 0.18[Formula: see text][Formula: see text]m CMOS technology. The simulation results show linear variation of duty cycle against external DC current over a range of 6.5–96%. The variation of square wave’s amplitude via bias current is found to be linear from 10[Formula: see text][Formula: see text]A to 80[Formula: see text][Formula: see text]A. Moreover, the proposed generator can operate very well up to 23.8[Formula: see text]MHz with nonlinearity less than 5%. The proposed generator circuit is also experimentally verified.

A tuneable active inductor employing DXCCTA: Grounded and floating operation

An active inductor employing both grounded as well as floating mode using Dual-X Current conveyor Transconductance Amplifier (DXCCTA) is presented in this article. The novelty of the proposed inductor topology is to exhibit simultaneously both positive and negative inductor characteristics without any change in the topology. In addition, active realization of positive and negative fractional order inductor are also presented. The performance characteristics of the proposed inductor models are verified using CMOS as well as Current Feedback Operational Amplifier (CFOA/IC AD844) based DXCCTA block. The compatibility of the proposed inductors is suitable for various application viz. active filter design using positive inductor and inductance cancellation using negative inductor. The theoretical explanations of the proposed designs are well verified through PSPICE simulations and experimental platform.

High CMRR Current-Mode Instrumentation Amplifier for Low Voltage and Low Power Applications

This paper introduces a current-mode instrumentation amplifier circuit which employs one modified dual-X current conveyor transconductance amplifier only. The proposed instrumentation amplifier circuit is operated at ±0.75 V and consumes maximum power of 0.64 mW only, thus suitable to low voltage, low power applications. The proposed circuit also has the feature of cascadability as outputs are explicitly taken from high output impedance terminals. The differential mode gain of the proposed circuit is electronically tunable and less affected by the temperature variation. Additionally, differential mode gain is bandwidth independent as well. Moreover, the common mode rejection ratio of the circuit is 175 dB at lower frequencies and remains as high as 38 dB at 100 MHz. The non-ideal and parasitic analyses of proposed instrumentation amplifier are also discussed. The effects of threshold voltage variation of MOS transistors on differential mode gain are further examined. PSPICE simulations with 0.13 µm CMOS process parameters are performed to confirm the theoretical proposals. Furthermore, the proposed circuit is also tested experimentally via commercially available ICs (AD844 and LM13700).

Low Voltage Operated Current-Mode First-Order Universal Filter and Sinusoidal Oscillator Suitable for Signal Processing Applications

This paper introduces a current-mode first-order universal filter which is realized using single modified dual-X current conveyor transconductance amplifier and two capacitors only. The circuit configuration is appropriate to monolithic integration. The circuit enjoys benefits of low input and high output impedances making the circuit easily cascadable, electronically tunable pole frequency and low operating supply voltages. The non-ideal and parasitic analyses of the circuit are explored. The cascadability of proposed first-order filter is verified by realizing a second-order all-pass filter. Additionally, one application of proposed first-order universal filter in terms of voltage-mode sinusoidal oscillator is also presented. The oscillator circuit provides two 180° out of phase voltage signals, simultaneously. The output voltage signals are obtainable from low impedance terminals. To validate the proposed circuits, HSPICE simulations are done. Moreover, to explore the practical aspects of proposed circuits, experimental results of first-order universal filter for all-pass function and second-order all-pass filter, are carried out by using commercially available ICs.

Electronically Tunable First-Order Filters and Dual-Mode Multiphase Oscillator

This paper introduces two novel circuits of first-order universal filter that comprise single multiple outputs dual-X current conveyor transconductance amplifier and one grounded capacitor only. The first circuit is of current-mode type, and second is of transadmittance-mode type. Both the circuits are suitable to modern IC technology and offer the feature of ease of cascadability. The proposed circuits do not need any passive component matching constraints. Moreover, the pole frequency of both the circuits is electronically tunable. The transadmittance-mode type circuit also provides an interesting feature of electronic and independent tuning of amplitudes of output currents without affecting the pole frequency. To check the applicability of the proposed circuit, a dual-mode multiphase oscillator is also derived from the proposed transadmittance-mode type filter. It provides two quadrature voltage outputs and four quadrature current outputs simultaneously. The oscillation frequency and condition of oscillation are orthogonally and electronically controllable. The non-ideal and parasitic analyses of all the proposed circuits are investigated, and HSPICE simulation results are depicted to confirm the proposed theory. Furthermore, transadmittance-mode type first-order universal filter is experimentally verified using commercially available ICs.

A novel electronically controlled Schmitt trigger with clockwise and anticlockwise hystereses

A novel circuit of Schmitt trigger employing a prototype of dual-X current conveyor transconductance amplifier and one grounded resistor is proposed in this paper. The main focus of the paper is towards the practicality of the proposed Schmitt trigger using the prototype of DXCCTA which is realized using commercially available ICs. The proposed circuit is easily cascadable. Both clockwise and anticlockwise hystereses are achievable simultaneously from the proposed circuit. The threshold levels and amplitudes of output currents are independently and electronically controllable. The non-ideal and parasitic studies of the proposed Schmitt trigger are investigated. Moreover, the application of Schmitt trigger as zero crossing detector is explored which enriches the applicability of the proposed circuit. Experimental results are depicted to verify the proposed Schmitt trigger circuit. Measured results show the good tuning of amplitude of output current for a wide range of 50 µA to 1.5 mA.

A novel linear square/triangular wave generator with tunable duty cycle

A novel circuit of square/triangular wave generator consists of single multiple output dual-X current conveyor transconductance amplifier (MO-DXCCTA), one grounded resistor and one grounded capacitor is proposed. One square wave in current mode and one triangular wave in voltage mode are simultaneously available from the proposed generator. The proposed circuit is fully electronically controllable facilitating the feature of duty cycle adjustment. The duty cycle is electronically tunable via bias current. Moreover, a wide sweep of oscillation frequency is possible via grounded capacitor with very good linearity. The tuning of oscillation frequency does not affect the amplitudes of output waveforms. Furthermore, the oscillation frequency can also be controlled electronically and independently via bias current for a fixed duty cycle of 50%. A prototype of MO-DXCCTA using commercial ICs (AD844 and LM13700) is used to carry out the experimental results. Measured results show very good variation of frequency (up to 245.5 kHz) against capacitor with nonlinearity less than 2%.

Novel CMOS Dual-X Current Conveyor Transconductance Amplifier Realization with Current-Mode Multifunction Filter and Quadrature Oscillator

This paper presents a novel active element, namely dual-X current conveyor transconductance amplifier. The CMOS implementation, parasitic model and characteristic performance parameters of the proposed dual-X current conveyor transconductance amplifier have been explored. The proposed active element has the advantages of good operational bandwidth, good dynamic range and low power consumption. Additionally, current-mode multifunction filter and quadrature oscillator are proposed to examine the applicability of the newly proposed active element. The proposed current-mode multifunction filter provides the responses, low-pass, high-pass and band-pass simultaneously without any circuit modification. The proposed quadrature oscillator circuit simultaneously generates three current outputs and three voltage outputs. The non-ideal analyses of both current-mode multifunction filter and quadrature oscillator are also included. Moreover, the active and passive sensitivities of both current-mode multifunction filter and quadrature oscillator are calculated which are found to be less than unity in magnitude. HSPICE simulation results are depicted to confirm the theoretical analyses. Moreover, practicality of novel dual-X current conveyor transconductance amplifier is examined through the experimental results of the proposed quadrature oscillator.

Novel electronically controlled current-mode Schmitt trigger based on single active element

In this paper, a simple circuit of current-mode Schmitt trigger consists of only single dual-X current conveyor transconductance amplifier (DXCCTA) is proposed. The proposed Schmitt trigger does not need any passive component for its realization. Its threshold levels and output current amplitude are electronically and independently adjustable with the help of corresponding input bias currents. The proposed circuit also has the features of good operational frequency range, ease of cascadability and low power consumption. The effects of non-idealities of DXCCTA and the effects of MOS transistors mismatch on the proposed Schmitt trigger are investigated. Moreover, the output current amplitude is less affected by temperature variation. HSPICE simulation results are shown to verify the performance of the proposed Schmitt trigger.