大电流宽频带热释电红外探测器优化设计

本文提出了一种大电流宽频带的热释电红外探测器的优化设计方法.在分析热释电输出电压响应的基础上,结合热辐射探测的特点,提出了新的仿真模型,实际电路与仿真数据基本吻合.通过采用双极型结型场效应管(BJFET)和改变热释电时间常数等方法解决了热释电前置放大器输出信号弱和通频带窄的关键问题.     

提高热释电红外感应器灵敏度的分析与对策

热释电红外传感器是一种被动式调制型温度敏感器件,利用热释电效应,通过目标与背景的温差来探测目标。热释电红外传感器在电子防盗、人体探测器领域中,应用很广泛,通过分析热释电红外传感器输出信号的特性,着重通过提高热释电感应器的性能来提高传感器的灵敏度。     

电流模精密整流电路

由电压型运算放大器组成的精密整流电路要严格地匹配电阻才能获得精密全波整流波形．本文给出一种具有CCⅡ电路特性由运算放大器AD844所构成的电流模精密整流电路．无需匹配电阻就可输出良好的精密全波整流波形．且具有输入电压范围大，频带宽等特点．     

双微分保护电路

目前国内外所生产的热电转换测量仪器中,对热电偶采用的保护电路有多种多样,但从原理上讲基本上可以分为双极性峰值检波保护电路和红外保护电路。双极性峰值检波保护电路位于输入衰减器和热电偶之间,以双极性峰值检波放大器监测输入电压,通过该保护电路控制衰减器和热电偶的通断,达到保护作用。这种电路简单、成本低。但只能用于10MH_Z以下。红外保护电路用红外感应元件监测热电偶的温升(见图1)。当输入电压超过量程,热电偶的温度将急剧升高时,紧贴热电偶外壳上的红外感应元件探测到这一温度变化,其直流电压输出增大,其信号经放大后,驱动相应的     

基于运放测试大输入范围ADC电路的设计

为测试大输入范围的ADC电路,综合考虑测试机的输出信号能力以及ADC输入范围要求,设计出合适的放大电路来扩展ATE输出信号范围,并根据噪声分析理论以及ADC电路参数测试对运放性能的要求选择前端驱动放大器。通过测试ADI公司AD7894的实例对比使用两种不同运放电路的实际测试效果表明计算公式有效可行,放大器的分析选择科学合理,为基于运放扩展ATE输出信号范围测试大输入范围ADC电路的设计提供可靠依据。     

热释电红外探测材料的研究进展

热释电红外探测材料主要分为热电堆型、热敏电阻型和热释电型，本文综述了热释电红外热探测材料的种类、性能和研究进展。     

解析媒体矩阵（Media Matrix）（八）——DEVICE的原理和使用（6）

自动增益控制AGC 自动增益控制原本是一个普通的电路模型,在大量的电子设备中都使用它。在一个简单的负反馈放大电路中,AGC可以根据前级输入的电平大小自动控制输出端的放大量:当输入信号降低的时候,AGC电路使得放大器提高输出增益;而当输入信号升高的时候,AGC又使放大器的输出增益降低,这样通过反复的、动态的调节,放大器就能“自动适应”     

Design of a rail-to-rail operational amplifier for implantable neural signal regeneration systems

为满足治疗中枢神经损伤的植入式神经信号再生系统的低压低功耗要求,设计了该微电子系统的中间级放大和激励的核心电路——恒跨导轨到轨运算放大器.根据系统满摆幅和低功耗的特点,在电路设计中采用了工作在亚阈值区的电流开关跨导控制电路作为输入级,改进的前馈AB类放大器作为输出级.芯片采用中芯国际0.18μm 1P6MCMOS工艺设计完成.仿真和测试结果表明,芯片实现了满摆幅动态范围,跨导恒定,可用于对探测得到的微弱神经信号的放大和激励,满足神经信号再生系统的要求.此芯片电路功耗和体积都很小,满足生物体植入式器件的要求.     

用于冶金现场气体浓度检测的脉冲调制型近红外光电传感器

提出了一种脉冲调制型近红外光电传感器,用于冶金现场气体浓度检测。介绍了其工作原理和结构组成。通过选择合适的电阻参数,可使得电路输出信号与探测距离成正比,实现了微弱信号的放大。实验证明系统工作稳定,可满足不同气体浓度的测试要求。     

基于比率法的高精度电桥电路及其应用

提出一种基于比率法的高精度电桥电路,用于测量电阻传感器中的高精度电阻。该电桥电路是基于模数转换器的数字量输出,采用模拟输入电压与参考电压比率的方法,将电桥的不平衡输出经放大后作为模数转换器的模拟量输入,将电阻式传感器相同一侧另一桥臂两端的电压差经放大后作为模数转换器的参考电压,经过模数转换后两者比率的数字量作为系统的输出。经过该电路处理后,电阻信号与系统的输出之间成线性关系,并克服了供电电压波动对电阻测量结果的影响,消除了系统的零点漂移和温度漂移。该电桥电路具有高准确度的电阻测量性能。     

基于超薄钽酸锂晶片及炭黑红外吸收层的热释电探测器

基于钽酸锂(LiTaO3)的热释电探测器具有灵敏度高、热释电系数大、响应范围宽等优点而被广泛应用于非分光红外气体检测.在LiTaO3热释电探测器制备过程中,采用预置沟槽方法制备出约20μm厚的超薄LiTaO3晶片,该方法既能控制晶片厚度又能实现自动解片,简化了探测器制备工艺;采用电喷雾方法制备出炭黑红外吸收层,该方法工艺简便,制备的吸收层分布均匀,结构疏松.电喷雾时间为20 min时制备的吸收层在常用气体吸收波段(2.5~10μm)的红外吸收率达98%以上,使探测器信号幅值提高了约2.6倍.热释电探测器性能测试结果表明:单元结构探测器的黑体探测率可达1.78×108cm·Hz1/2/W;二元补偿结构探测器信噪比为单元器件的2倍;将二元补偿结构探测器应用于非分光红外气体测试系统,进行了SO2气体检测,等噪声检测下限约为1×10-6.     

Novel pseudo RMS current converter for sinusoidal signals using a CMOS precision current rectifier

A very simple pseudo RMS-to-DC current converter for sinusoidal signals is described. The most salient feature of the circuit is that it uses a CMOS precision current rectifier consisting of only two transistors and thus operates throughout in the current domain. The full-wave rectifier was built using CD4007 devices and tested. It was observed that the transfer curve is sharp even at low nanoampere input levels. The converter is expected to work up to 100 kHz.<>     

A linear operational transconductance amplifier for instrumentationapplications

A linear operational transconductance amplifier (OTA) is described that consists of a linear transconductor and a translinear current gain cell followed by three current mirrors. The proposed circuit has superior linearity and temperature characteristic when compared with the commercially available OTA. A prototype circuit with a transconductance of 50 μS has been built with discrete bipolar transistors producing a linearity error of less than ±20% over an input voltage range from -0.8 to 0.8 V. The prototype OTA circuit also exhibits a transconductance that is linearly dependent on a bias current varying over four decades with a sensitivity of 1 S/A     

A Compact Dual-Port Multi-Band Rectifier Circuit for RF Energy Harvesting

This paper presents a compact multi-band rectifier with an improved impedance matching bandwidth. It uses a combination of п–matching network (MN) at Port-1, with a parallel connection of three cell branch MN at Port-2. The proposed impedance matching network (IMN) is adopted to reduce circuit complexity, to improve circuit performance, and power conversion efficiency (PCE) of the rectifier at low input power. The fabricated rectifier prototype operates at 0.92, 1.82, 2.1, 2.46 and 2.65 GHz covering GSM/900, GSM/1800, UMTS2100, and Wi-Fi/2.45–LTE2600. The size of the compact rectifier on the PCB board is 0.13λ_g × 0.1λ_g. The fabricated rectifier achieved an RF-to DC (radio frequency direct current) PCE of 31.8%, 24%, 22.7%, and 15%, and 14.1% for −20 dBm at the five respective measured operating frequencies. The circuit attains a peak RF-to-DC PCE of 82.3% for an input power of 3 dBm at 0.92 GHz. The proposed rectifier realizes an ambient output dc voltage of 454 mV for multi-tone input signals from the two ports. The rectifier drives a bq25504-674 power management module (PMM) to achieve 1.21 V from the two-port connection. The rectifier has the ability to exploit both frequency domain through the multi-band operation with good impedance bandwidth and a spatial domain using dual-port configuration. Hence, it is a potential candidate for various applications in radio frequency energy harvesting (RFEH) system.     

Evaluation of a pyroelectric detector with a carbon multiwalled nanotube black coating in the infrared

The performance of a pyroelectric detector with a carbon multiwalled nanotube coating was evaluated in the 0.9-14 microm wavelength range. The relative spectral responsivity of this detector was shown to be flat over most of the wavelength range examined, and the spectral flatness was shown to be comparable to the best infrared black coatings currently available. This finding is promising because black coatings with spectrally flat absorbance profiles are usually associated with the highest absorbance values. The performance of the detector (in terms of noise equivalent power and specific detectivity) was limited by the very thick (250 microm thick) LiNbO3 pyroelectric crystal onto which the coating was deposited. The responsivity of this detector was shown to be linear in the 0.06-2.8 mW radiant power range, and its spatial uniformity was comparable to that of other pyroelectric detectors that use different types of black coating. The carbon nanotube coatings were reported to be much more durable than other infrared black coatings, such as metal blacks, that are commonly used to coat thermal detectors in the infrared. This, in combination with their excellent spectral flatness, suggests that carbon nanotube coatings appear extremely promising for thermal detection applications in the infrared.     

A feedback-controlled ferroresonant voltage regulator

A new regulated rectifier which combines a ferroresonant regulator with a simple control circuit is described herein. The voltage regulating function normally provided in a ferroresonant regulator by the saturating core is provided by the control circuit in this new regulated rectifier. The control circuit provides regulation by varying the amplitude of the alternating voltage feeding the rectifier and filter. By incorporating feedback into the control circuit, regulation of better than ±1/2 percent for line, load, frequency, and temperature changes can easily be attained. The new feedback-controlled circuit retains many desirable properties of conventional ferroresonant regulators such as half-cycle transient response, good input power factor, ideal output waveform for rectification and filtering, high efficiency, short circuit protection, and suppression of input voltage spikes. Additional features are level set, improved efficiency, lower stray magnetic fields than observed with conventional ferroresonant regulators, and, primarily, precision regulation. Data on an 800-watt regulated rectifier employing the new circuit are also presented.     

Novel zero voltage switching dual-switch forward converter with ripple current cancellation

A zero voltage switching (ZVS) dual-switch forward converter with ripple current cancellation is presented. In the proposed converter, active clamp circuit is used to clamp the voltage stresses and to realise ZVS of all switching devices. Active clamp boost converter with power factor correction is used in the front stage of the proposed converter to draw a sinusoidal line current from the AC source and to maintain a constant voltage at the DC bus. The second stage of the proposed converter is a dual-switch forward converter with current doubler rectifier to obtain the isolated low output voltage. Active clamp circuit used in the DC/DC converter can recycle the energy stored in the leakage inductor and magnetising inductor so that the voltage stresses on the switches are limited and the ZVS feature is realised. The current doubler rectifier offers the ripple current cancellation at the output capacitor and reduces the current stress of the transformer secondary winding. The circuit configuration and principle of operation are analysed and discussed in detail. Experimental results with a laboratory prototype based on a 90-260 V_rms input and 12 V/30 A output were provided to verify the effectiveness of the proposed converter.     

Optical signal processing in dual-wavelength optoelectronic drop analyzer

Dual-wavelength optical signals are injected into the liquid drop through optical fibers in order to study the light intensity variation during the drop growth. Modulation and demodulation are used to reduce the influence of ambient light on the valuable optical signals. HA17555 chip composes the oscillating circuit for light modulation, with different high oscillating frequency for different light source. The light signal collected by a fiber detector after propagation inside the drop is changed into electric signal through the OPA2111 photoelectric circuit. The second-order band-pass filter composed of MAX275 chip is used for signal-separation. The high-pass filter is used to prevent the low frequency signal of ambient light. The valuable signal related to the drop is demodulated by a linear demodulation circuit including a half-wave rectifier, full-wave composition and low-pass filter.     

Optimization and improvement of thermal energy harvesting by using pyroelectric materials

We deal with the thermal energy which is one of the ambient energy sources surely exploitable, but it has not been much interest as the mechanical energy. In this paper, our aim is to use thermal energy and show that it’s an important source for producing the electrical energy through pyroelectric effect which is the property of some dielectric materials to show a spontaneous electrical polarization versus temperature. In this context, we present a concept to harvest a thermal energy using infrared rays and pyroelectric effect.The pyroelectric material used in this work can generate an electrical voltage when it subjected to a temperature change which will be ensured by the use of infrared lamp. Our experimental results show that the electrical voltage, current and harvested power increased significantly when increasing the area of the pyroelectric element. The experimental results show also that with this simple concept we harvested a heavy amount value of power which will certainly be useful in an extensive range of applications, including sensors and infrared detection. These results shed light on the thermoelectric energy conversion by Ceramic lead zirconate titanate (PZT) buzzer having the pyroelectric property.     

Analysis and implementation of soft switching converter with series-connected transformers

The system analysis and design consideration of a zero voltage switching (ZVS) converter with series-connected transformers are presested. Based on the operational behaviour, each transformer in the adopted converter can be operated as an inductor or a transformer. Therefore no output filter inductor is needed in the adopted converter. To reduce the voltage stress of the switching device in the conventional forward converter, an active snubber based on a clamp switch and a clamp capacitor is used to recycle the energy stored in the transformer leakage. During the transition interval, the resonance based on the junction capacitance of switches and transformer leakage inductance can achieve ZVS operation of switches. The centre-tapped rectifier is used at the secondary side to achieve full-wave rectification. The operating principles, steady-state analysis and design equations of the proposed converter are provided. Finally, experimental results for a 100 W (5 V/20 A) prototype circuit are provided to verify the converter performance.