Nigar Minhaj

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.

Current conveyor-based voltage-mode two-phase and four-phase quadrature oscillators

A voltage mode two-phase quadrature oscillator using plus-type second generation current conveyors [CCIIs(+)] is realized by using a simple technique. The basic building block for this technique is a voltage mode non-inverting band-pass filter. The two-phase quadrature oscillator is then transformed into a four-phase quadrature oscillator by replacing the two CCIIs(+) by two dual output, current conveyors [DO-CCIIs]. The proposed circuits enjoy attractive features such as use of grounded passive components, independent frequency control, outputs of almost equal magnitude and low sensitivity figures. Both the oscillator circuits are designed and verified using PSPICE simulation.

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...

Transconductance Element-Based Non-inverting and Inverting Precision Full-Wave Rectifier Circuits

A three-output transconductance element (TE) with two complementary MOS transistors and a grounded resistor are used to realize a non-inverting and an inverting precision full-wave rectifiers. The attractive features of the proposed full-wave rectifier circuits are high input impedance, large input operating range from -500mV to 500mV, high frequency operation upto 200MHz, low zero crossing distortion, linearity, low component count and suitability for IC fabrication. SPICE simulation results are included to verify the proposed circuits.

A TUNABLE QUADRATURE OSCILLATOR WITH ONLY TRANSCONDUCTANCE ELEMENTS AND GROUNDED CAPACITORS

A novel quadrature oscillator is realised with only transconductance elements (TEs) and grounded capacitors. The realised quadrature oscillator uses only two inverting and two non-inverting transconductance elements, along with two grounded capacitors. The quadrature oscillator enjoys the attractive features of low component count, independent frequency tuning and suitability for integration in MOS technology.

Multioutput Current-Controlled Current Conveyor-Based Function Generator

A multioutput current-controlled current conveyor (MOCCCII)-based function generator is proposed, which provides a mixed-mode sinusoidal four-phase quadrature outputs, square and triangular voltage outputs simultaneously. The starting building block of the proposed function generator is a single output current-controlled current conveyor (CCCII)-based voltage-mode sinusoidal quadrature oscillator (VMSQO). The VMSQO consists of a CCCII(+), two CCCII(-) and two grounded capacitors. The VMSQO is then transformed into a function generator with sinusoidal four-phase quadrature voltage outputs, four-phase quadrature current outputs, square and triangular wave outputs by replacing the CCCII(+) and a CCCII(-) by MOCCCIIs with additional two grounded resistors and a MOCCCII-based integrator. The proposed circuit enjoys attractive features such as wide range electronic tunability, almost equal magnitude voltage and current outputs, load insensitive current outputs, low sensitivity figures and use of grounded passive components. The proposed circuit is verified by using Spice simulation.

GENERALISED IMPEDANCE CONVERTERS WITH ONLY TRANSCONDUCTANCE ELEMENTS AND GROUNDED CAPACITORS

Novel generalised impedance converters are presented, which use only transconductance elements and/or grounded capacitors for the realisation of a wide variety of immittance functions. The generalised impedance converters can be used in the realisation of low sensitivity continuous time filters. The use of transconductance elements and grounded capacitors in the realisation of continuous time filters lend to electronic tunability and compatibility to integration in contemporary IC technologies. The generalised impedance converters are also verified using PSPICE-based simulation.