SachchidaNand Shukla

Review: Comparison of QRS detection algorithms

An Electrocardiogram (ECG) is graphical representation of the electrical movement of human heart and used in diagnosis of various heart diseases. The primary function of ECG analysis is correct detection of QRS complex and other ECG characteristics [1]. In this review paper, researchers provide a comparative study between four popular algorithms: namely Window pair algorithm, Dynamic Plosion Index algorithm, KNN algorithm, Slope vector waveform algorithm [2-5] against three assessment criteria 1) Cross Validation, 2) Threshold and 3) Robustness to noise in order to obtain a fast, robust and highly accurate QRS detection algorithm which helps in the development of a more robust clinical instrument by making the front end signal processing more effective [6].

Two-stage small-signal amplifier with Darlington and Sziklai pairs

A New circuit model of two-stage small-signal amplifier using Darlington and Sziklai pairs is proposed for the first time. Proposed circuit is obtained by cascading a small-signal Darlington pair amplifier with that of Sziklai pair based small-signal amplifier with minor modifications. Proposed amplifier essentially uses two additional biasing resistances in its design. It crops considerably high voltage and current gain (345.523 and 464.357 respectively) with audible range bandwidth of 43.363 KHz for AC input signals swinging in 10-30mV range at 1KHz or lower frequency. Proposed circuit-architecture successfully removes the poor response problem of conventional Darlington pair amplifiers at higher frequencies and narrow bandwidth problem of recently announced (by authors) circuits of small-signal Sziklai pair amplifier. Variations in voltage gain with frequency and various biasing components like biasing resistances, DC supply voltage and coupling capacitors are discussed in length. Temperature sensitivity of performance parameters, THD and small-signal AC equivalent circuit analysis of the proposed circuit are elaborately studied. Proposed design can be implemented in cascadable gain blocks for receivers, 715Hz-44KHz frequency range power sources and in the circuits where reproduction of signal with simultaneously high voltage and current gain is the prime requirement.

A New Circuit Model of Small-Signal Amplifier Using MOSFETs in Triple Darlington Topology

A small-signal amplifier with three identical MOSFETs in Darlingtons topology is proposed and qualitatively analyzed perhaps for the first time. Unlike CS- MOSFET amplifiers, the voltage gain of the proposed circuit is found considerably higher than unity. This amplifier can be used to amplify audio range signal excursions swinging in 0.1- 2mV range. In the narrow-band performance range, the proposed amplifier produces simultaneously high voltage and current gains with low harmonic distortion. These properties offer a flexible application range to the proposed circuit as high-voltage-narrow-band amplifier in permissible audio- frequency range. An additional biasing resistance RA is to be essentially used in the proposed circuit to maintain its voltage/current amplification property. Variations in voltage gain as a function of frequency and different biasing resistances, temperature dependency of performance parameters like voltage gain, bandwidth, current gain, input/output noises and total harmonic distortion of the amplifier are perused to provide a wide spectrum to the qualitative studies.

Development and Qualitative Analysis of a New Circuit Model of Two-Stage Small-Signal Sziklai Pair Amplifier

New circuit model of a two-stage small-signal Sziklai pair amplifier is proposed for the first time. The proposed amplifier circuit, which is obtained by cascading a small-signal Sziklai pair amplifier (Stage-1) with triple-transistor based compound Sziklai amplifier (Stage-2), is analyzed on the qualitative scale. Performance of the proposed amplifier is compared with that of Stage-1 and Stage-2 amplifier circuits to provide a wide spectrum to the qualitative studies. Proposed amplifier uses three additional biasing resistances in its circuit configuration and crops high voltage gain (237.50), high current gain (339.98) with wider bandwidth (2MHz) in 1-15mV range of AC input at 1 KHz. The proposed circuit successfully removes the poor response problem of conventional Darlington pair amplifiers at higher frequencies and narrow bandwidth problem of recently developed (by authors) circuit of small-signal Sziklai pair amplifier. Variation in voltage gain as a function of frequency and different biasing resistances, bandwidth and harmonic distortion of the amplifier is also pursued. The proposed amplifier may be useful for those applications where high voltage and current gain would be the prime requirement of amplification in a wider frequency range, spanned approximately from 200Hz to 2.5MHz.

New small-signal amplifying system with Sziklai pairs in triple-transistor topology

A new small-signal amplifying system with Sziklai pairs in triple transistor topology is proposed and qualitatively analyzed for the first time. Proposed amplifier design may be used at preamplifier stage of EEG, Radio/TV receivers and other audible frequency range communication systems. Combination of Q1-Q2 transistors in the proposed design constitutes PNP Sziklai pair whereas Q2-Q3 together acts as NPN Sziklai pair. Circuit successfully amplifies audio range signals swinging in 1μV-10mV range. It produces high voltage gain (190.95), current gain greater than unity (7.208), 250.83 KHz bandwidth, low harmonic distortion (0.817%) and can be tuned in 41Hz-250KHz frequency range. Resistance RA in the design is essential to maintain its voltage/current amplification property whereas REX can be optionally used. Proposed circuit is free from the poor response problem of small-signal Darlington pair amplifiers at higher frequencies and narrow bandwidth restrictions of recently announced PNP and NPN driven small-signal Sziklai pair amplifiers. Tuning performance, variation of voltage gain with frequency and different biasing resistances, small-signal AC analysis, harmonic distortion, temperature dependency of performance parameters and input/output noises of the circuit are widely discussed.

Design and analysis of low power CMOS ECG amplifier

This paper deals with the design and analysis of CMRR of Electrocardiogram (ECG) amplifier at different W/L of CMOS and Vdd. ECG measurement setup consists of electrodes to measure the ECG signal from the human body, an analog front end (AFE) amplifier that amplifies the ECG signal, analog to digital converter (ADC) for digitizing the analog ECG signal, and a display device to monitor the patients heart regularly. The common mode rejection ration of ECG is increase with increasing vdd. CMRR of ECG at W/L= (37/27) of NMOS at different Vdd is increase with increase vdd. All the simulations are performed on 180nm CMOS technology with the supply voltage of 1.8V.

Novel circuit of small signal amplifier with BJT-MOSFET hybrid unit in sziklai pair topology

BJT-MOSFET hybrid combination is used in Sziklai pair topology to design a novel circuit model of small-signal amplifier. Proposed amplifier can be tuned in 47KHz-245KHz frequency range. This circuit can amplify audio range signals swinging in 0.01-2mV range at 1KHz with an additional biasing resistance RA. Proposed amplifier with high voltage gain (347.995), current gain greater than unity (71.519), 47.926KHz bandwidth and 1.33% THD gives better results than recently announced small-signal Sziklai pair amplifier. Qualitative features and analysis of the amplifier suggests its suitability to use in Radio/TV receivers, low frequency power sources and other audible range communication applications.

Dielectric and Optical Study of Polymer Nematic Liquid Crystal Composite

The dielectric anisotropy and dispersion of the real and imaginary part of the permittivity of commercially important nematic mixture E-24 and its polymer composite were investigated in the frequency range from 1 kHz to 10 MHz, and temperature range 14℃ to 55℃. The percentage optical transmittance and density have also been measured for both the systems. The results have been explained by assuming molecular rotation about the long molecular axis, under a hindering nematic potential. The dielectric anisotropy Δe is positive, and the mean dielectric permittivity falls with rising temperature. Δe is also used to determine the order parameter with varying temperature.