Muslim T. Ahmed

On transconductance-C quadrature oscillators

Two circuits of Electronically Tunable Quadrature Oscillators (ETQOs) are given, which only use operational transconductance amplifiers (OTAs) and capacitors. In these circuits, a wide range of linear ƒo-tunability is present with bias voltage/current control of the OTAs. Outputs of equal amplitude, but in quadrature, are available in both the ETQOs. The circuits have a low component count, attractive sensitivities and suitability to implementation in monolithic MOS technology. Experimental results are included in support of the theory.

Tunable OTA-based multiphase sinusoidal oscillators

Using a simple scheme, realisation of some novel multiphase sinusoidal oscillators (MPSOs) employing operational transconductance amplifiers (OTAs) as the active device are considered. These oscillators can provide n signals (n being odd) equal in amplitude as well as equally spaced in phase. Two practical OTA: RC three-phase oscillators have been realised and studied in detail. Their corresponding OTA-C realisations have also been obtained. Both the circuits enjoy low component count, low sensitivity performance and wide range electronic tunability. The OTA-C oscillators are highly suitable for monolithic implementation in MOS-form.

A simple realisation scheme for OTA-C universal biquadratic filter

A simple scheme for realising four standard second-order voltage transfer functions, viz., low-pass, highpass, bandpass, and band-elimination is presented. It is implemented by using only operational transconductance amplifiers and capacitors to realise two universal biquadratic filters (UBFs), i.e. UBF-I and UBF-II. The UBF-I can also be converted into a sinusoidal oscillator by simply grounding a suitable node. The circuits have the attractive features of wide-range electronic tunability of its pole frequency, bandwidth and pole Q; these can also be programmed digitally. In addition, the filters enjoy excellent sensitivity performance and are suitable for monolithic MOS or Bi-MOS implementation. The effects of non-ideal buffer on the performance of the circuits are studied.

First Order Current Mode Filters and Multiphase Sinusoidal Oscillators Using MOCCIIs

An insensitive current mode versatile first order filter section with single input and multiple outputs is realized. The realization uses two multi outputs current conveyors, only one grounded resistor and one grounded capacitor. The realized current mode section provides low-pass, high-pass and all-pass responses at different outputs without any component matching constraint. The all-pass section is then cascaded with the current mode non-inverting integrator to realize a current mode multiphase sinusoidal oscillator. Thus the realized current mode oscillator provides eight phase sinusoidal outputs with equal magnitudes. The current mode outputs are loaded with same valued resistive load to achieve the eight phase voltage mode sinusoidal outputs with equal magnitudes. All the realization were designed and simulated using PSPICE. The simulation results thus obtained, verify the theory.

Novel technique for immittance simulation—realisation of some all-active simulators

Two novel and generalised schemes are given for the realisation of grounded and floating immittance simulators. The use of operational transconductance amplifiers (OTAs) lends wide range electronic tunability to the schemes. The first scheme is particularly used in the realisation of new all active device ideal grounded inductance and super inductance simulators. These circuits employ only an OTA along with an operational amplifier (OA) modelled in its first pole roll-off characterisation. Similarly, the second scheme is used in realising novel ideal floating inductance and super inductance simulators. The all active device floating simulators only require a simple matching constraint to be satisfied in its realisation. Both the circuits use only active devices and have wide range linear electronic tunability and reliable high frequency performance. The effects of non-ideality of the OAs on the circuit performance is also examined. The simulators are highly suitable for monolithic implementation in either...

Wide range electronically tunable component multipliers

An operational transconduciance amplifier (OTA)-based good quality, wide-range electronically tunable module for resistance and capacitance multipliers has been realized. Its multiplication factors are conveniently tunable with the bias-control current or voltage of the OTA over three decades. The module with slight modifications realizes temperature-insensitive multipliers. The circuit is very suitable for microminiaturization and is expected to find wide practical applications. Experimental results are also included.

Wide-range electronically tunable multifunctional OTA-C filter for instrumentation applications

A simple scheme is presented for realizing four standard second-order transfer functions, i.e. low-pass, high-pass, bandpass, and band-elimination. The system is implemented using only operational transconductance amplifiers (OTAs) and capacitors. The resulting circuit has the attractive feature of wide-range electronic tuning of pole frequency, bandwidth, and pole Q. These parameters may also be programmed digitally. The OTA-C filter achieves excellent sensitivity performance and is suitable for monolithic IC implementation.

Electronically tunable first-order OTA-capacitor filter sections

Electronically controlled first-order building blocks, using only operational transconductance amplifiers and capacitors, are realized and studied. The circuits exhibit convenient control of circuit parameters with the help of external voltage or current control. Each circuit uses a low component count and has low sensitivity performance. The basic blocks can be used for the realization of higher-order electronically tunable filters.

A novel direct reading active-RC system for measurements of in-circuit, discrete, and incremental capacitances

A simple, low-component active-RC circuit is given for the measurement of in-circuit, discrete, and incremental capacitances. The measurement circuit provides the measured value of capacitance directly in terms of the circuits output voltage. The proposed system provides good accuracy for these measurements. The capacitance measurements are independent of the signal frequency. Experimental results that support the theory are included. >

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.