Chopping Technique Research Articles

Aligned chopping for full thickness fragmentation in hard cataracts

We describe a horizontal chopping technique to fracture the nucleus using an angled sharp edged chopper, thats enters the anterior chamber through a side port in a 30° angle to the main incision. Following the capsulorrhexis, the phaco tip is buried into the nucleus centrally, while the surgeon-bent chopper is placed behind the lens on the opposite side of the main incision. When moving the chopper towards the phaco tip, the angle allows a sharp clean cut of the hard nucleus, dividing it in 2 hemispheres and consequently further in smaller fragments.

Mutfak Çalışanlarının Doğrama Tekniklerine Yönelik Kavramsal Değişim Süreçlerinin İncelenmesi

Conceptual change can be expressed as changing the errors in the concepts used in scientific and applied fields within the scientific framework. Within the scope of the study, misconceptions about chopping techniques, which are basic concepts in the science of gastronomy, have been determined. The field study was carried out with 39 kitchen workers operating at the level chef (chef de partie), who had not previously received formal gastronomy training. In the study, remarkable levels of misconceptions about chopping techniques were reached. In order to prevent misconceptions in the research, it has been concluded that the formal and non-formal gastronomy education should be supported with special education methods (collaborative education model, project-based education model, inquiry-based education model, problembased education model, out-of-class education model and 5E-7E education model).

A 101 dB SNR fourth-order ΣΔ modulator for MEMS digital geophones

A fourth-order ΣΔ modulator (SDM) applied for micro-electro-mechanical systems (MEMS) digital geophones is presented in this paper. At the system stage, the proposed fourth-order SDM adopts a hybrid path technology including a feedforward path and a feedback path. At the design stage, a class AB operational transconductance amplifier with a gain bootstrap structure and chopper technique is employed in the first-stage integrator, which can achieve high DC gain, GBW, (Slew Rate) SR and reduce flicker noise, ensuring high (Signal-to-Noise Ratio) SNR for the proposed SDM. Meanwhile, other key modules are designed to meet basic requirements and achieve low power consumption at the same time. The proposed SDM was implemented in the SMIC 0.18 μm CMOS technology and its final area is 3.09 mm2. When the sampling frequency of 512KHz and signal bandwidth of 2KHz are adopted, the measured results show that the proposed fourth-order SDM can achieve SNR of 101 dB and ENOB of 16.4 bits with less than 5mW power consumption, which meet the requirements of high dynamic range and low power in MEMS digital geophones.

Randomized Controlled Trial Comparing Femtosecond Laser-Assisted with Conventional Phacoemulsification on Dense Cataracts

To compare the benefit of femtosecond laser-assisted cataract surgery (FLACS) versus phacoemulsification (PE) and 2 fragmentation patterns in managing dense cataracts. Randomized controlled trial. Patients with nuclear opacity (NO) grade >5 (Lens Opacities Classification System III) were enrolled at the Singapore National Eye Centre. Patients who were unsuitable for FLACS, whose corneal endothelial cell count (ECC) was <1,500 cells/mm2, or had cataracts with additional complexities were excluded from the study. Eyes were randomized to PE, 600μm grid (FLACSg), or 16-segment fragmentation (FLACS16) in 2:1:1 ratio. The Victus (Bausch & Lomb) laser platform and insitu phacoemulsification chop technique was used. Data for patient demographics, preoperative, and 1month postoperative best-corrected visual acuity (BCVA), ECC, effective phacoemulsification time (EPT), and perioperative complications were collected. Outcome measurements were the loss of ECC at 1month and EPT. Ninety-three patients were randomized to PE (48), FLACSg (22), and FLACS16 (23). Majority were Chinese (87; 93.5%). Mean age was 74.3 ± 8.8 years of age. Cataracts were mostly graded as NO 5-6 (49; 61.3%). EPT among treatment arms was not different (P= .097, one-way ANOVA) but was significantly higher for NO >6 than NO <6 (P < .001, general linear model). ECC loss was significantly less in FLACSg than in PE (P= .018, Bonferroni correction). Mean 1-month postoperative LogMAR BCVA (0.23 ± 0.20) was significantly better than preoperative BCVA (1.02 ± 0.85; P < .001, paired t test) but not different between PE and FLACS. FLACSg but not FLACS16 significantly lowered the mean ECC loss during phacoemulsification in dense cataracts.

Design of a CMOS Lineal Hall Sensor Front‐End Working in Current Mode with Programmable Gain Stage for Power Specific Chip

With the continuous intelligentization of power systems, the demand for the integration of digital chips and sensor chips such as the Internet of Things is also increasing. A CMOS lineal magnetic Hall sensor front‐end working in current mode with programmable gain stage is designed and implemented with SMIC 55 nm standard CMOS technology. By using a spinning‐current technique, chopper technique, and digital calibration technique to eliminate the offset voltage and nonlinearity, this magnetic Hall sensor can be easily integrated into digital systems like SoCs. This work has already finished the circuit simulation and layout design, and all simulation indicators basically reach the expected value. The maximum gain of proposed sensor systems can be up to 33.9 dB. The total power is less than 4 mW. And the total area is less than 0.113 μm2. The magnetic Hall sensor can be easily integrated into chips such as the power Internet of Things to form a single‐chip‐level SoC design, which is mainly used in applications such as circuit breakers and electric energy measurement.

A brief note on Femtosecond laser-assisted cataract surgery

Femtosecond Laser-Assisted Cataract Surgery (FLACS) is an advanced modality for cataract surgery. Its advantage in cataract surgery in terms of reduction of ultrasound power is controversial. We believe this controversy is due to different techniques and different nuclear densities included in the studies. Our study evaluated the Effective Phacoemulsification Time (EPT) during phacoemulsification with or without Femtosecond laser technology in different nuclear densities. The study comprised two main groups: Conventional phacoemulsification and FLACS groups. We stratified all eyes included in the study into soft and hard cataracts, and we employed the vertical quick chop technique for nucleus disassembly in all cases. In the FLACS group, we used sextans in addition to 350 microns grid softening

Phaco chop versus stop and chop nucleotomy techniques: A comparative evaluation

To perform a comparative evaluation of phaco chop versus stop and chop nucleotomy techniques in phacoemulsification. Materials and Methods: 60 patients with uncomplicated senile cataract were included in this study which were randomly divided into phaco chop group (group 1) and stop and chop group. (group 2) with 30 patients each and each group had 10 patients each of nuclear sclerosis grade II, III and IV. The main parameters were effective phaco time, total balanced salt solution used, total phacoemulsification power, intraoperative complications and postoperative visual acuity on day 1, 1st week and 3rd week. Results: The mean effective phacoemulsification time was 30.33±3.77 seconds in group 1 and 31.63 ± 4.22 seconds in group 2. The mean total phacoemulsification power in group 1 was 38.97 ± 4.33% whereas 41.93 ± 7.09 % in group 2. The mean total BSSV used in group 1 was 111.67 ± 13.86 ml whereas 113.17 ± 19.94 ml in group 2. The difference between the two groups was not significant. All patients received BCVA of 6/6 in both the groups after 3 weeks. Conclusion: The stop and chop technique and phaco chop technique are equally efficacious for nuclear cracking in patients in terms of visual acuity but if we compare according to nuclear grading, stop and chop technique requires more phaco power, phaco time and balanced salt solution which can lead to higher endothelial cell loss in grade IV nuclear cataract. Keywords: Cataract, Nucleotomy, Phacoemulsification, Phaco chop, Stop and Chop.

Evaluation of corneal endothelial cell changes in diabetic patients before and after phacoemulsification surgery: A comparative study

Aim: The study was conducted to evaluate and compare the changes in corneal endothelial cell count density (ECD) and Central corneal thickness (CCT) between diabetic and non diabetic population before and after phacoemulsification surgery. Settings and Design: This prospective, comparative, interventional study was carried out at government medical college and attached group of hospitals, a tertiary eye care centre in Rajasthan, India. Materials and Methods: A total of 50 patients with type II diabetes mellitus (age group 30-80 years) and 50 age matched healthy patients of senile cataract with clear cornea without any other ocular pathology were non-randomly selected for Phacoemulsification surgery (phaco) after detailed preoperative assessment. All patients were operated by the same surgeon with phaco chop technique to exclude any surgeon’s related bias. Endothelial cell count, CCT and Coefficient of Variance (CV) was measured with specular microscope pre-operatively and postoperatively at day 1st, 7th, 15th, 1 month, and 3 months serially. Result: Postoperatively, the mean ECD was decreased in both the groups but loss of endothelial cell count was significantly more in diabetic population as compare to non diabetic groups at day 1, day 7, day 15, 1 month and 3 months. CCT was increased on first post-operative day in both the groups, subsequently decreased and then returned back to about same as pre-operative state after 1 month. But postoperatively, the change in mean CCT was not significant between both groups. The difference in % CV was significantly higher in diabetic group as compared to non diabetic group postoperatively. Conclusion: The corneal endothelial cell changes were significantly high in diabetic population as compared to nondiabetic patients. The ECD loss, increase in mean CCT and % CV were more in diabetic population as compared to non diabetic. And patients with diabetes showed slower recovery in endothelial healing as compared to non diabet

Comparison of phacoemulsification parameters in eyes with and without exfoliation syndrome

To evaluate and to compare the phacoemulsification machine parameters in eyes with and without XFS, requiring cataract surgery. Patients who underwent phacoemulsification and in-the-bag IOL implantation for cataract were included in this retrospective study. All surgeries were performed by the same experienced surgeon using the stop & chop technique with the same phacoemulsification device (Infiniti Vision System, Alcon Laboratories, Inc., USA). Patients were divided into two groups according to the presence of exfoliation material (XFM). Each group consisted of consecutive patients. Their characteristics and intraoperative phacoemulsification parameters were compared. Sixty-eight eyes of 68 patients [29 in the exfoliation syndrome (XFS) (-) group, 39 in XFS (+)] were enrolled. There were no statistical differences regarding preoperative patient characteristics. There was a statistically significant difference in total U/S time, phaco time, aspiration time and estimated fluid used between the XFS (+) and XFS (-) groups (P=0.021, P=0.017, P=0.009 and P=0.002, respectively). Considering that the use of a CTR (capsule tension ring) might be an important factor potentially affecting surgical parameters, the data were analyzed accordingly. Aspiration time and estimated fluid used remained statistically significant (P=0.046 and P=0.017, respectively); however, although the U/S total and phaco time were found to be longer in XFS (+) group compared to XFS (-) group, the difference did not show statistical significance (P=0.061 and P=0.059, respectively). There were no differences between groups regarding endothelial cell loss or any other postoperative complications. The presence of XFS results in longer total U/S time, phaco and aspiration time and more estimated fluid used in phacoemulsification, but this prolongation does not result in additional complications.

A ±0.15% RH Inaccuracy Humidity Sensing System With ±0.44 °C (3σ) Inaccuracy On-Chip Temperature Sensor

This article describes a high accurate humidity sensing system. The humidity sensor and the interface circuit of our system-in-package (SiP) are 3-D stacked to optimize integration density with small foot print. A single reconfigurable ADC is utilized for both 3-D stacked humidity and on-chip temperature sensors. An incremental <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Delta \Sigma $ </tex-math></inline-formula> ADC with a reconfigurable <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Delta \Sigma $ </tex-math></inline-formula> modulator is employed with dual input stages. With the combination of chopping, correlated double sampling (CDS), dynamic element matching (DEM), and system-level chopping techniques, high accuracy sensing system is achieved. The interface circuit, implemented in a standard CMOS <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.18~\mu \text{m}$ </tex-math></inline-formula> CMOS technology, occupies an area of 1.24 mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\mathbf {2}}$ </tex-math></inline-formula> . The SiP sensing system dissipates only <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$146.5~\mu \text{A}$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$25~\mu $ </tex-math></inline-formula> A from 3.3 V supply and 1.8 V supply, respectively. Its humidity inaccuracy is 0.15 %RH with a resolution of 0.012 %RH, while a temperature inaccuracy is 0.44 °C ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3\sigma $ </tex-math></inline-formula> ) with a resolution of 0.015 °C.

Rotary Chop: A New Technique for Teaching Chop and Tackling Mature Cataracts.

IntroductionHere we describe a new cataract chop technique that is most valuable for two groups of ophthalmologists: (1) experienced surgeons encountering challenging nuclear fragmentation due to mature cataracts or zonulopathies, and (2) inexperienced surgeons wishing to develop skills necessary for chopping techniques.MethodsWe have termed this new method “rotary chop,” since the partial thickness pilot holes created by the phacoemulsification (phaco) tip around the periphery of the nucleus produce a rotary phone dial appearance on the surface of the cataract. By creating these pilot holes, the surgeon is able to easily place the chopper deep into the body of the nucleus, avoiding the need to apply vertical piercing force to the nucleus.ResultsThe patient in the technical video had a 4+ nuclear sclerosis cataract. The preoperative vision in this eye was counting fingers at 2 feet with no improvement with refraction. On postoperative day 1, visual acuity had improved to 20/80 . By postoperative week 1, best-corrected visual acuity was 20/20 (20/25-2 uncorrected).ConclusionThis method avoids unnecessary zonular stress. Additionally, inexperienced surgeons using this technique during routine cataract surgery are able to quickly master the movements necessary for both vertical and horizontal chop in a safer environment.Electronic supplementary materialThe online version of this article (10.1007/s40123-020-00249-7) contains supplementary material, which is available to authorized users.

A low-power second-order sigma-delta modulator for MEMS digital geophones

This paper presents a low-power second-order sigma-delta modulator (SDM) for micro-electromechanical systems (MEMS) digital geophones (DGPs). The proposed SDM optimizes the performance of the first stage integrator and uses an adaptive class-AB current recycling operational transconductance amplifier (OTA) to improve the current efficiency. In addition, gain-enhancing circuits are applied in the OTA to increase the DC gain, and the chopper technique is used in the first stage integrator to reduce the flicker noise. The proposed SDM was implemented in the SMIC 0.18 μm CMOS technology and occupies an area of 0.82 mm2. The simulation results reveal the signal-to-noise ratio (SNR) was 76.46 dB and the effective number of bit (ENOB) was 12.4 bits. Measurements show that the SNR was 57.5 dB and the ENOB was 9.26 bits with a sampling rate of 256 kHz, an oversampling ratio 128, and a signal bandwidth of 1 kHz. The proposed SDM has a supply voltage of 1.8 V and a power consumption of 193.5 μW, which is suitable for the low-power MEMS DGPs applications.

The effect of phacoemulsification of bilateral cataracts, performed at different intervals, on the macular area of the retina

Purpose. A comprehensive assessment of the state of macular retina after phacoemulsification of two eyes performed at different intervals between operations according to optical coherence tomography (OCT) data. Materials and methods. We examined 93 patients (186 eyes) aged 65.7 ± 1.6 years with bilateral age cataract after phacoemulsification of both eyes performed at different intervals between the operations: 1–5 days — 22 patients (44 eyes), 1–3 weeks — 31 patients (62 eyes), 4 or more weeks — 40 patients (80 eyes). Before surgery, visual acuity of the first eye was, on average, 0.38 ± 0.05, while that of the second eye averaged 0.41 ± 0.05. The operations were performed on the «Infiniti Vision System» (Alcon) phacoemulsifier by Ozil technology through a corneal tunnel 2.2 mm long by one and the same surgeon with no complications. The Phaco chop technique was used. All patients underwent retinal examination by Optovue Avante OPT (OPTOVUE, USA) according to the scanning Protocol Raster and, partly, by Retina map (including central retinal thickness and volume of the macula in the 5 mm zone) before the operation, and 1, 2, 4, 12 weeks after surgery, on both eyes. Results. Before surgery, the average central retinal thickness and the volume of the retina in the area of 5 mm, in both operated eyes were almost identical: the first eye revealed 271.0 ± 7.5 μm, and 5.625 ± 0.040 mm3, the second one revealed 270.0 ± 8.5 μm, and 5.628 ± 0.040 mm3. In the postoperative period, the results showed no statistically significant differences (p &gt; 0.05) between the central retinal thickness and volume in the 5 mm zone before and after surgery in both eyes, regardless of the intervals between operations. Conclusion. The absence of a significant difference in the macular retina response to surgery, confirmed by OCT data, indicated the safety of operations on both eyes regardless of the intervals between them.

Tilt-and-crush: A safe, effective and energy-saving technique for soft cataract removal.

The tilt and crush technique is a modified chopping technique developed mainly to maximize safety and effectiveness in emulsifying soft cataracts. After clear corneal incision and continuous curvilinear capsulorhexis, the hydro-dissection cannula is introduced under the anterior capsule about 90 degrees to the axis of the main wound and injection of fluid is continued until the distal pole of the nucleus prolapses out of the capsulorhexis rim into the anterior chamber. The centre of the nucleus is then engaged with the phacoemulsification tip using high vacuum and tilted vertically in the anterior chamber. The second instrument is passed behind the full length of the vertically tilted nucleus to crush it against the phacoemulsification tip. This technique was successfully performed in 517 eyes by a single experienced surgeon. The mean effective phaco time was 0.11 ± 0.32 s, and it was zero in 382 (73.9%) eyes. The mean total phaco time was 4.79 ± 10.71 s. In 322 (62.3%) eyes, no phaco energy was utilized to remove cataract. None of the eyes experienced any complication during or after the surgery. This safe and reliable technique is significantly more energy-efficient compared to other traditional techniques like divide-and-conquer and phaco-chop. Unlike, some widely known pre-chopping techniques, it can be taught easily with good reproducibility.

Phacomulsification in senile white mature cataracts;its safety and efficacy

Abstract&#x0D; Purpose &#x0D; To evaluate the intraoperative difficulty, complications and post operative outcome in patients with white mature cataracts undergoing phacomulsification and foldable intraocular lens implantation and to develop a strategy for achieving continuous curvilinear capsulorhexis in these cases.&#x0D; Study design&#x0D; Descriptive case series&#x0D; Place and duration &#x0D; Ophthalmology department of Holy family hospital, Rawalpindi in six months interval since January 2017 to June 2017&#x0D; Material and Methods &#x0D; 50 Patients who had senile white mature cataract were enrolled in this prospective study .Detailed preoperative and intraoperative notes were made. A small capsulorhexis was attempted initially after staining capsule with trypan blue .An initial cut was made with cystotome and it was enlarged with utrata forceps. Endophacomulsification was done with stop and chop technique. Intraoperative difficulties related to continuous curvilinear capsulorhexis, phacomulsification and post operative visual outcomes were analyzed.post operative examinations were done at day 1,1st week,1st month and 3rd month.&#x0D; Results&#x0D; There were 28 males (56%) and 22 females (44%).The mean age was 63.18±7.997 standard deviation years(48-78).The mean preoperative best corrected visual acuity BCVA was 0.0276±0.013 (SD)Snellen, decimal(0.01-0.05) and the mean post operative BCVA was 0.638±0.305 (SD) Snellen, decimal(0.1-1.0) .Mean phaco time was 4.08±1.03 (SD)mins(2.08-6.66).The mean preoperative intraocular pressure IOP was 15.90±1.799 (SD)mmHg (12-22) and mean post op IOP was 11.98±2.035 (SD) mmHg(10-18) .Posterior capsular rupture occurred in 3 (6%) , vitreous loss occurred in 1 (2%) patients. 5 (10%) cases were converted to extra capsular cataract extraction (ECCE). Postoperatively 10 (20%) patients had transient corneal edema, 3 patients (6%) had persistent corneal edema and corneal burn treated with steroids and hyper osmotic agents.&#x0D; Conclusion &#x0D; The intraoperative and postoperative complications rate is higher in white mature cataracts. White mature cataract is a challenge for cataract surgeon, yet by means of additional dyes and proper techniques and expertise, the rate of complications can be reduced.&#x0D; Keywords&#x0D; Phacomulsification, continuous curvilinear capsulorhexis, senile mature cataract, trypan blue, posterior capsular rupture, persistent corneal edema

Fully Integrated Dual-Mode X-Band Radar Transceiver Using Configurable Receiver and Local Oscillator

In this paper, a fully-integrated dual-mode X-band radar transceiver that supports Doppler radar and frequency modulated continuous wave (FMCW) radar is proposed. To remove large off-chip DC-blocking capacitors in the Doppler mode, the double-conversion technique and local oscillator (LO) chopping technique are introduced. These techniques remove the DC offset and makes the transceiver more robust to the TX to RX leakage. In addition, they also improve the noise figure (NF) by filtering out 1/f noise of the analog baseband. The FMCW radar is realized using a direct-conversion receiver and a chirp generator. The chirp generator consists of a frequency sweep generator (FSG) and a fractional-N phase-locked loop (PLL). All the analog baseband components including a programable gain amplifiers (PGA) and 1/R 4 range compensation filters are integrated on the chip as well as a bandgap and low-dropout regulators. The operating frequency is from 9.7 to 12.3 GHz, which consumes 216 mW in Doppler mode and 201.6 mW in FMCW mode from a 1.2-V supply voltage. The maximum chirp bandwidth is 750 MHz and the maximum receiver gain is 76 dB with 6-dB gain step. The chip size of the transceiver is 7.68 mm 2 including all the pads.

Scoop and chop - A modified phaco-chop technique for pseudoexfoliation and cataract.

PURPOSE:The purpose is to evaluate the results of the modified direct phaco-chop technique of cataract surgery in eyes with pseudoexfoliation.METHODS:All patients with pseudoexfoliation and visually significant cataract with normal intraocular pressure (IOP) and optic nerve that underwent cataract surgery by the same surgeon using Infiniti®, OZil® Torsional handpiece (Alcon Labs), were included for this retrospective hospital-based study. Direct vertical or horizontal chop technique was used in all cases with parameters set as required for quadrant removal with high vacuum after the initial cleanup of cortex under the capsulorhexis. To allow better visualization of the hardness of the nucleus core, the sides of the lens were scooped out a central well with vacuum with maximum chopping done centrally within the rhexis as the first step to enable better assessment of the depth of burying the chopper for direct chop. Intraoperative details recorded and analyzed included ultrasound time and cumulative dissipated energy. The mean visual acuity and IOP before and after surgery were recorded at 1 day, 1 week, and 1 month. Complications during or after surgery were noted.RESULTS:A total of 138 patients with a mean age of 62 ± 6.7 years underwent phachop technique of phacoemulsification for nuclear cataract grades of nuclear sclerosis 2–4 with significant improvement in visual acuity from baseline (0.26) to 3 months (0.82), P < 0.001. The mean ultrasound torsional amplitude and cumulative dissipated energy (CDE) were greater for brown cataract of grading >3, P = 0.02. A total of 8 patients had intraoperative zonular dialysis in 1 quadrant (none in >1 quadrant), which was not associated with intraoperative vitreous prolapse in 6 eyes.CONCLUSIONS:Direct modified phaco-chop technique may be a safe technique in pseudoexfoliation due to minimal zonular stress with successful outcomes and reduced complications.

Vapor chopped MgO thin film optical waveguide

Abstract In optoelectronic devices, optical signal transmission gets more affected due to the useof materials and their properties. Here, prepared magnesium oxide (MgO) thin films were studied for optical waveguide application by measuring their optical signal transmission loss (OSTL). Novel vapor chopping technique (VCT) was used to prepare vapor chopped (VC) MgO thin films and properties of those films were compared with as deposited or non-chopped (NC) films. Various oxidation temperatures (573, 623 and 673 K) and thin film thickness variation effect on the OSTL were studied. The VC MgO thin film waveguide showed a smaller transmission loss as compared to the NC MgO thin film waveguides. An AFM study showed that, surface roughness of VC thin films was lower than the NC MgO thin films and it increases with increase in oxidation temperatures.

Low-Noise Chopper-Stabilized Multi-Path Operational Amplifier with Nested Miller Compensation for High-Precision Sensors

This paper presents a low-noise multi-path operational amplifier for high-precision sensors. A chopper stabilization technique is applied to the amplifier to remove offset and flicker noise. A ripple reduction loop (RRL) is designed to remove the ripple generated in the process of up-modulating the flicker noise and offset. To cancel the notch in the overall transfer function due to the RRL operation, a multi-path architecture using both a low-frequency path (LFP) and high-frequency path (HFP) is implemented. The low frequency path amplifier is implemented using the chopper technique and the RRL. In the high-frequency path amplifier, a class-AB output stage is implemented to improve the power efficiency. The transfer functions of the LFP and HFP induce a first-order frequency response in the system through nested Miller compensation. The low-noise multi-path amplifier was fabricated using a 0.18 µm 1P6M complementary metal-oxide-semiconductor (CMOS) process. The power consumption of the proposed low-noise operational amplifier is 0.174 mW with a 1.8 V supply and an active area of 1.18 mm2. The proposed low-noise amplifier has a unit gain bandwidth (UGBW) of 3.16 MHz, an input referred noise of 11.8 nV/√Hz, and a noise efficiency factor (NEF) of 4.46.

Design and Analysis of a Microwave-Optical Dual Modality Biomolecular Sensing Platform

A combined microwave-optical biomolecular sensor with high sensitivity and selectivity is presented. The microwave sensor characterizes the dielectric properties of a medium using the oscillation frequency shift. To improve the sensor sensitivity beyond the 1/f <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> phase noise limit, a quadrature-oscillator-based reactance sensing scheme is proposed, which attenuates the 1/f <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> noise by 20 dB/decade. Further sensitivity enhancement is realized by a novel chopping technique that modulates the free-running frequencies of the coupled oscillators differentially while maintaining a fixed locking frequency. To achieve a higher selectivity, optical sensors are introduced to target specific biomolecules. Utilizing single-photon avalanche diodes, they detect both photon intensity and photon emission time. A biosensor prototype was fabricated in a 28 nm CMOS technology. The microwave sensor achieves 0.2 ppm/√Hz frequency sensitivity with 11.5 mW power consumption. The optical sensor shows 500/s dark count rate and 300 ps timing jitter at 1 V excess bias. A protein thermal denaturation experiment confirms the sensitivity and selectivity enhancement of the dual-modality biosensing platform.