锁定放大是微弱信号检测的重要手段。基于相关检测理论，利用开关电容的开关实现锁定放大器中乘法器的功能，提出开关电容和积分器相结合以实现相关检测的方法，并设计出一种锁定放大器。该锁定放大器将微弱信号转化为与之相关的方波，通过后续电路得到正比于被测信号的直流电平，为后续采集处理提供方便。测量数据表明锁定放大器前级可将10-6 A的电流转换为10-1 V的电压，后级通过带通滤波器级联可将信号放大1×105倍。该方法在降低噪声的同时，可对微弱信号进行放大，线性度较高、稳定性较好。 Abstract: Lock-in Amplifying（LIA）is one of important means for weak signal detection. Based on cross-correlation detection theory， switch in the swithched capacitor was used as multiplier of LIA， and a new method of correlation detection was proposed combining swithched capacitor with integrator. A kind of LIA was designed which can convert the weak signal to square-wave， then DC proportional to measured signal was obtained through follow-up conditioning circuit， providing convenience for signal acquisition and processing. The measured data shows that the electric current（10-6 A） can be changed into voltage（10-1 V） by LIA， and the signal is magnified 1×105 times by cascade band-pass filter. The noise is suppressed and the weak signal is amplified. It has the advantages of good linearity and stability.
上传时间： 2013-11-29
上传用户：黑漆漆
The latest generation of Texas Instruments (TI) boardmountedpower modules utilizes a pin interconnect technologythat improves surface-mount manufacturability.These modules are produced as a double-sided surfacemount(DSSMT) subassembly, yielding a case-less constructionwith subcomponents located on both sides of theprinted circuit board (PCB). Products produced in theDSSMT outline use the latest high-efficiency topologiesand magnetic-component packaging. This providescustomers with a high-efficiency, ready-to-use switchingpower module in a compact, space-saving package. Bothnonisolated point-of-load (POL) switching regulators andthe isolated dc/dc converter modules are being producedin the DSSMT outline.TI’s plug-in power product line offers power modules inboth through-hole and surface-mount packages. The surfacemountmodules produced in the DSSMT outline use asolid copper interconnect with an integral solder ball fortheir
上传时间： 2013-10-10
上传用户：1184599859
Features: High efficiency, high reliability, low cost AC input range selected by switch 100% full load burn-in test Protections: Short circuit / Over load Fixed switching frequency at 25KHz Cooling by free air convection 1 year warranty Dimensions: 199*98*38mm (L*W*H)
标签： Switchin Output Single SKS
上传时间： 2013-10-30
上传用户：taa123456
Demonstration circuit 1562A is an engineering toolto design and evaluate the LTC699X-X family ofTimerBlox circuits. The center section of the boardcontains a pre-configured TimerBlox function.DC1562A comes in twelve timing function variationsas outlined in Table 1.Surrounding the center board is a ”playground”prototyping area. The prototyping area has padsfor Dip-8, S8, MS8, or S6 packages with breadboarding connections to each pin and two convenientpower buses and ground bus surrounding theentire area. This area is for conditioning signals tocontrol the timer function and for adding loads controlled in time.
上传时间： 2013-10-18
上传用户：如果你也听说
为了提高PCB板制作的效率，改变传统的化学腐蚀制板工艺，使用机械仿形铣制作电路板的方法，设计了以ATMEGA16单片机为核心部件的PCB板雕刻机控制系统。其中包括PCB雕刻机的基本功能、主要硬件电路设计和软件的实现流程，并给出了相关设计电路。重点分析了雕刻机步进电机的驱动电路以及主轴电机的驱动电路，该雕刻机经实际运行，系统工作良好，可有效提高PCB板的制作效率。 Abstract: In order to improve the efficiency of production of PCB board and change the traditional chemical etching plates， using of mechanical copying milling method makes circuit boards，this paper introduces the PCB engraving machine control system used ATMEGA16 microcomputer as the core components. It includes basic function， the hardware circuit design and software realization process， and gives the corresponding circuit design.It analyses the drive circuit of engrawing machine stepper motor and spindle motor in detail. This engraving machine by practical operation， the system works well， which can effectively improve the production efficiency of PCB board.
上传时间： 2013-10-17
上传用户：liangliang123
Designing read/write device (RWD) units for industrial RF-Identification applications is strongly facilitated by the NXP Semiconductors HITAG Reader Chip HTRC110. All needed function blocks, like the antenna driver, modulator demodulator and antenna diagnosis unit, are integrated in the HTRC110. Therefore only a minimum number of additional passive components are required for a complete RWD. This Application Note describes how to design an industrial RF-Identification system with the HTRC110. The major focus is dimensioning of the antenna, all other external components including clock and power supply, as well as the demodulation principle and its implementatio
上传时间： 2013-10-22
上传用户：zhengjian
针对煤矿井下调度及紧急救援系统的需求，以DTMF编解码模块为核心，设计了具有自动拨号功能的新型电话系统。该系统利用MT8880对DTMF信号的编解码功能实现一键拨号和远程设置，通过检测振铃和忙音信号，完成自动摘机和挂机过程，配合AGC等外围电路达到话音清晰流畅的效果。 Abstract: To meet the demand for mine scheduling and emergency rescue system， with using DTMF signal codec as the core， a new telephone system was designed with automatic dialing function. In the system， the DTMF signal encoding and decoding function of MT8880 was used to achieve one-touch dialing and remote setting. The circuit detects the ringing and busy signal， and then completes automatic off-hook and hangup. With AGC(Automatic Gain Control) and other peripheral circuits， the voice was regulated to a clear and smooth effect.
上传时间： 2014-11-18
上传用户：ly1994
Designing Boards with Atmel AT89C51,AT89C52, AT89C1051, and AT89C2051 for Writing Flash at In-Circuit Test. Recent improvements in chips and testers have made it possible for the tester to begin taking over the role tradi-tionally assigned to the PROM program-mer. Instead of having a PROM pro- grammer write nonvolatile memories before assembling the board, the in-cir- cuit tester writes them during in-circuit testing operations. Many Teradyne Z18- series testers are now in use loading code into nonvolatile memories, micro- controllers and in-circuit programmable logic devices. The purpose of this note is to explain how the Z18 approaches the writing task for Atmel AT89C series IC’s, so that designers of boards using these chips can get the best results.
上传时间： 2013-11-17
上传用户：xiaozhiqban
为解决电致变色器件的颜色变化受外界环境颜色控制的问题，设计了一种基于单片机的便携式颜色自适应识别电路。与传统颜色识别电路相比较，该电路利用数字式的颜色传感器来获取外界环境颜色，产生的数字颜色信号易于单片机进行处理。在电路中，下位机部分主要负责获取电致变色器件变色参数及控制电致变色器件的颜色变化;而上位机部分主要负责把下位机获取的电致变色器件变色参数进行电压到颜色的曲线拟合，并通过蓝牙通信把拟合曲线参数传递给下位机。结果表明，该电路能自动根据环境颜色提供-4~4 V范围步进为0.1 V的电压来驱动电致变色器件的颜色显示，与传统的颜色识别电路设计相比，识别的精度和速度都得到了明显改善。 Abstract: In this paper， a portable adaptive circuit for color identification(PACCI) based on MCU was designed. Compared to the traditional color identification circuit， the PACCI adopts digital sensor to detect the color data from external environment and further generate digital color data， which can be processed easily by MCU. In PACCI， the slave is mainly responsible for detecting the color parameters of the corresponding elcreochromic device and further driving it. For the master， which is mainly responsible for the color curve fitting based on the parameters of the electrochromic device， and transmits the fitting parameters to the slave through the bluetooth device. The results show that the PACCI can provide the basis voltage range from -4V to 4V automatically based on the colors of external environment with step as 0.1V to drive the corresponding electrochromic device. Compared to the traditional color recognition circuit， the recognition accuracy and speed of PACCI have been improved significantly.
上传时间： 2013-11-09
上传用户：franktu
现有基于MAX7219芯片的数码管驱动电路只适用于小尺寸LED，为扩展其使用范围，在介绍动态显示芯片MAX7219功能的基础上，提出了一个基于该芯片的8位高亮度8英寸数码管驱动电路。电路保留了MAX7219芯片的功能强大、编程简单等优点，通过74LS273锁存器和ULN2803达林顿驱动器，实现了对任意大尺寸数码管提供较高电压和电流驱动的静态显示，并亮度可调。 Abstract: The existing display-driving circuit based on MAX7219 was only applicable to small-size LED. To expand its use, based on the function introduction of dynamic display chip MAX7219, a display-driving circuit for high-brightness 8-bit LED with the size of 8-inch was proposed. The advantages of MAX7219 were retained, such as powerful function and simple programming. Static display with adjustable brightness for large-size LED with higher voltage and current was achieved with the help of 74LS273 and ULN2803.
上传时间： 2013-10-23
上传用户：31633073
