Publications in IEEE

Analysis of Continuous-Time SD-modulator With Single-Bit Quantizer Operating at Limit CycleLimit cycle mode is an underdeveloped concept that promises certain benefits like jitter immunity and reduction of power per conversion bandwidth in continuous time Sigma-Delta Modulators. In this paper an analysis of the limit cycle mode will be conducted and synthesis method will be showcased. The synth esis includes the out-of-band gain theory and the describing functions method to derive the mathematical description of the system. A numerical example is provided to showcase the entire procedure.

Design of Continuous-Time ΣΔ-modulator With Single-Bit Quantizer With Hysteresis Operating at Limit CycleThis paper presents a novel design methodology of a Continuous-time ΣΔ-Modulator operating at a limit cycle. The methodology employs both the describing functions linearization method and the out-of-band gain theory to find the parameters of the loop filter. As a result of the unification a single mathematical description of the loop requirements is obtained as a system of inequalities. Each of the solutions of the inequalities represents a possible modulator. An example is provided to demonstrate the design process.

Frequency compensation in a two-integrator loop Gm-C biquad when realized with single stage OTAsThe paper considers the design of a two-integrator loop Gm-C second order filter, realized by single stage operational transconductance amplifiers (OTA). Two major problems are discussed: equalizing the maxima of OTA input voltages and unfavorable effect of OTA input capacitances. It is shown OTA input capacitances cause increasing of pole Q-factor and may turn the circuit to unstable. A method for avoiding of this problem is proposed, which could be applied for the other circuits of this class.

Analysis of the Effect of Transit Capacitances in Fully Differential Operational Transconductance AmplifiersThe paper considers the analysis of influence the transit capacitances, connecting input and output nodes in fully differential (FD) operational transconductance amplifiers (OTA) and having effect basically in single-stage OTAs. First is shown the incompleteness of the often used approach of representing of these capacitances by a positive zero of OTA transconductance. Then are proposed single-ended equivalent circuits for both cases when FD OTA is used as inverting and non-inverting amplifier. They simplify the analysis, which is demonstrated by considering of two examples: single OTA with different loads and a gyrator resonance circuit.

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