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"Operational amplifiers"
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Novel Class-AB Operational Amplifier for Compact and Energy-Efficient Wake-Up Sensor Systems
This paper presents a novel rail-to-rail Class-AB operational amplifier tailored for wake-up systems in motion sensor applications. By addressing limitations in free Class-AB designs, such as large inrush current, unstable bias conditions, and area ineffiiency, the proposed design achieves a gain of 59 dB and unity gain frequency of 550 kHz driving a 5 pF load. The inrush current is reduced from 1 mA to 7 µA, increasing the battery life. The layout area is reduced by 53% compared to the free Class-AB design, making it highly suitable for compact implementations. Operating at a low power consumption of 2 µW with a 1.8 V supply, the amplifier achieves a Signal-to-Noise-and-Distortion Ratio (SNDR) of 22 dB. These advancements demonstrate the potential of the design for energy-efficient analog front-end solutions in IoT and portable systems.
Journal Article
Hands-On and Virtual Laboratories in Electronic Circuits Learning—Knowledge and Skills Acquisition
Hands-on and virtual laboratory-based learning has been integrated into science education due to its potential positive impact on students’ knowledge and skills development. In this study, we explore the effect of the hands-on and virtual laboratories on 152 undergraduate students’ conceptual knowledge, inquiry, and measurement skills acquisition in the domain of operational amplifiers (op-amps) circuit learning. Students were divided into two groups and performed individually three experimental exercises involving basic op-amps electronic circuits: students in the Hands-On group performed the exercises in a physical laboratory environment, while students in the Virtual group performed the exercises in a virtual environment with TINA-TI (v9) software. Pre-post tests were used to quantify student performance progress stemming from their laboratory-type activities. Based on our findings, knowledge was developed the most, followed by inquiry skills, and finally, skills related to measuring electronic current quantities in a circuit, F(2,456) = 44.183, p = 0.000. Additionally, an ANCOVA analysis comparing the means of the three exercises revealed that the group participating in hands-on activities outperformed the group engaged in virtual activities, F(1,152) = 9.039, p = 0.003. Finally, we recommend designing a curriculum that focuses on both cognitive growth and skills development in the domain of op-amps.
Journal Article
Cryogenic transimpedance amplifier based on a commercial operational amplifier
A transimpedance amplifier working at a temperature around 50 K has been developed. The design of the amplifier is targeted to use specifically in dry dilution refrigerators for measuring quantum devices. Electrical characteristics such as input noise, bandwidth, and gain of several commercial operational amplifiers (op amps) operating at 77 K were evaluated. From a screening process, the op amp OPA827 was chosen for the benchmarking of a cryogenic transimpedance amplifier. The conductance of a quantum point contact (QPC) at 100 mK was measured in a dry dilution refrigerator in order to compare the cryogenic and room temperature performance of transimpedance amplifiers built using OPA827. The results were analyzed with a noise model describing the measurement system. We found that it is more advantageous to use a cryogenic transimpedance amplifier when the impedance of the device under test is high as in the case for most quantum devices.
Journal Article
New Meminductor Emulators Using Single Operational Amplifier and Their Application
This paper presents operational amplifier-based meminductor emulator circuits. The two meminductor emulators have been realised using a single operational amplifier, one memristor, three resistors, and two capacitors whereas the third emulator is designed using an operational amplifier, two memristors, two resistors and two capacitors. The proposed meminductor emulator circuits are very simple as compared to most of the circuits reported in the literature. The behaviour of proposed meminductor emulators is found to be satisfactory over a wide range of frequencies. The proposed meminductor emulators have been designed and simulated using the LTspice tool. A chaotic oscillator has been designed to check the performance of a proposed meminductor emulator.
Journal Article
Low-noise amplification of voltage response for thermopile optical detectors
A technique is presented to amplify the voltage response of thermopile optical detectors. It is based on the parallel combination of multiple operational amplifiers. The background noise of the voltage response has been deceased, which significantly improves the repeatability of the measurement results. Thus, this technique enables the same detector to measure weaker optical power or irradiance at the same precision level. The corresponding amplifying circuit is designed and fabricated. For the same detector, the experimental results show that the standard deviation of the background noise of the combined n op-amps is about 1 / n lower comparing with the conventional single op-amp scheme, which is consistent with the theoretical expectations. Furthermore, the lasers of 10 μW and 1μW were also measured by the specific detector and the amplifier circuit. For a 10 μW response, the measurement repeatability of the 8-combined op-amps is about 1.4%, which is better than the 3.3% of a single op-amp. For 1 μW laser, the measurement result of voltage response of the 8-combined op-amps can be precisely quantified; however, the result of the single op-amp is hardly distinguished. The presented technique based on multiple op-amps is practical and can be potential in many applications. We hope this technique could offer help for expanding the measurement ranges of thermopile optical detectors at weaker optical power and irradiance.
Journal Article
Redesign of the AD820 Single-Channel Circuit for the Development of the ARD820 Low-Noise Rail-to-Rail Operational Amplifier
The task of this study was to design and later produce a low-power (single supply 5–30 V, dual supply ± 2.5 V and ± 15 V) rail-to-rail operational amplifier aRD820 with low voltage noise (<4 µV, p-p. 0.1 to 10 Hz), ultralow input bias current (< 15 pA), and low offset voltage (< 500 µV) characteristics. Similar characteristics are presented by Analog Devices chip AD820. Thus, the task of the design team was to adapt the prototype circuity of AD820 to our technological capabilities, modify the circuit, if necessary, and eliminate any deficiency of the prototype. The input stage module got source followers at the input of the operational amplifier. The second stage module was modified to be more symmetric. The output stage module obtained additional resistors and capacitors to achieve frequency compensation. One FET transistor in the current reference module was substituted with other elements. Simplified electric schemes of these modules of AR820 and aRD820 are presented. The performance of modules of modified electric schemes was tested in Simulink software. Simulations of the full electric scheme for aRD820 demonstrated characteristics similar to those of AD820 data tables. Later production of the aRD820 chip and measurements demonstrated that the planned characteristics of the operational amplifier were met.
Journal Article
Water Temperature Measurement Method Based on Square-Wave Signal Generator
Water temperature measurement is widely used and plays an important role in fishery breeding, agricultural irrigation, temperature control of household water heater and other aspects. People have a huge demand for water temperature measurement devices. The performance of the existing device is greatly affected by the environment and often requires manual intervention. The square-wave signal generator has simple structure, stable output, low energy consumption, easy operation and low price. The water temperature measurement method based on the square-wave signal generator can expand the application range of the square-wave signal generator, promote the convenience of measurement work and then improve the measurement sensitivity. Based on operational amplifier, Schmitt-Trigger Inverter and 555 Timer, the output frequency of the circuit changes according to the change of the overall resistance value of the circuit. A waterproof thermistor is added to the circuit and placed in water. The water temperature would change the resistance value of the overall circuit by changing the resistance value of the thermistor. Therefore, different output frequencies of the measuring circuit reflect different water temperatures. The working principles of the above three measuring circuits are specifically described, and their measuring characteristics are compared. It can be seen that the circuit based on 555 Timer has stable measuring performance and high sensitivity, which can be widely applied to the needs of water temperature measurement in production and life. What’s more, it provides a new idea for water temperature measurement.
Journal Article