M.A. Siddiqi

Multi output filter and four phase sinusoidal oscillator using CMOS DX-MOCCII

A current mode versatile first-order filter section with single input and multiple outputs is realised. The realisation uses one dual-X second generation current conveyor, two grounded resistors and two grounded capacitors. The realised current mode section provides low-pass, high-pass and all-pass responses at different outputs. The all-pass section is then cascaded with a current mode non-inverting integrator to realise a current mode four-phase sinusoidal oscillator. The current mode outputs are resistively loaded to achieve the four phase voltage mode sinusoidal outputs. All the realisations were designed and then verified using PSPICE. Experimental verification of the proposed filter sections using commercially available AD844s further confirms the validity of the theory.

Tutorial review: Realization and performance assessment of active-R inductors

Inductance simulation has been a topic of considerable interest for researchers. In this review-cum-tutorial paper, new as well as available grounded and floating active-R inductance simulators are considered and critically studied. It is shown that simulators basically realize non-ideal inductors. A novel circuit for high-Q realization is given. Experimental results are also included.

CDTA based logarithmic amplifier

A logarithmic amplifier using current differencing trans-conductance amplifier (CDTA) is presented. Both current as well as voltage mode inputs are possible. Output can also be voltage or current. Owing to its current mode operation it consumes less power. Furthermore, the instability problem found in op-amp based logarithmic amplifiers due to the presence of an active element in the feedback loop is absent in the CDTA logarithmic amplifier. The simulation result confirms the logarithmic behavior with a very low-error. It also shows a good dynamic range.

Direct form active-R synthesis techniques and their critical assessment

A unified treatment is used to obtain the three active-R direct form synthesis approaches: the immittance (LC) simulation technique, the FDNR technique and the FDNC technique. All these methods are shown ultimately to require the active-R simulation of L, C, FDNR and FDNC elements. As simulated Ls and Cs are already available in the active-R form, this aper considers active-R realizations of FDNR and FDNC elements in grounded and ungrounded modes. These techniques are critically analysed in the light of available simulations. Experimental investigations are also included

Effect of summer's pole on general active-R biquadratic filters

The effect of summers pole on the performance of an active-R general biquad is investigated. Results on the reliable high frequency range of such filters are obtained. Experimental verification of theory is included.

High bandwidth circuits for the measurement of small resistance changes

In this paper we present current-mode circuits for measuring small resistance changes such as in RTDs and strain gages. These circuits make use of current conveyors to achieve wider bandwidth in contrast to the conventional circuits which rely on opamps. Furthermore, it uses single calibrating resistor which can take care of many non-ideal effects on the part current conveyor and that due to tolerances of resistors and power supplies. Also, multiple sensors can be used in these circuits without having need of any additional circuit elements. Simulations performed using SPICE of the proposed circuits confirms the idea presented in this work.

FVF based CDTA and Its application

This paper presents a modified CMOS implementation of the current differencing trans-conductance amplifier (CDTA). It uses one current source and one current sink to get the current differencing action. The proposed circuit uses lesser number of transistors, offers higher bandwidth, apart from other qualities associated with them. An application of this CDTA in analog filter is also demonstrated. All the claims have been verified by SPICE program. The simulation results are in agreement with the theoretical results.

DXCCII based mixed-mode three phase oscillator

A mixed-mode three phase sinusoidal oscillator (MTSO) employing Second Generation Dual-X Current Conveyor (DXCCII) as the active element is presented. A feedback scheme consisting of two lossy integrators followed by a lossless inverting integrator is employed to obtain three voltage-mode and three current-mode sinusoidal signals simultaneously. The oscillation conditions and oscillation frequencies are independently controllable. The use of grounded passive elements ensures viability for monolithic integrated circuit implementation. Results of PSPICE simulations confirm the proposed theory.

Active-R Simulation of Ideal Grounded Capacitor

A circuit, basically, using three operational amplifiers and a resistor is given for the simulation of ideal grounded capacitor. Its application in realizing an active-R band-pass biter is experimentally demonstrated.

Simple C-Multiplier

A simple circuit is given for capacitance(C)-multiplication of grounded capacitor. It uses one operational amplifier (OA) in the unity-gain connection, two resistors and a grounded capacitor, of which C-value is to be multiplied. The theory is experimentally verified.