一种音频双通道增益平衡前置放大器的实现

介绍了一种具有自动音量增益匹配的双通道放大器。它一个通道的增益由另一通道的输入音量所决定，使两通道信号经放大后输出的强度基本一致，从而最大程度地消除音量失衡。测试表明，两个幅值相差20dB的语音信号经放大器调整后幅值相差1．51dB，听觉上已无差别。本放大器的这种功能给立体声拾音、扩声带来了最大的方便，具有很好的应用价值。     

浅析步进电机驱动器与步进电机的相互关系

由于步进电机系统具有开环控制精度高,控制形式较为简单,易于实现数字化控制等特点,从而在数控机床、自动化生产线、工业仪器仪表、计算机设备、医疗仪器、家电产品、舞台灯光等许多领域得到了广泛的应用,成为目前不可或缺的重要电机组件。步进电机从原理及结构上可分为反应式步进电机、永磁式步进电机、混合式步进电机以及特种步进电机等。从绕组个数上又可分为二相、三相、四相、五相、六相,直到九相步进电机等。我国的步进电机行业起步较早,并一度以反应式步进电机的生产与应用成为国际电机行业的一大特色,目前,仍有许多国内用户使用反应式步进电机。混合式步进电机的特点是力矩大、运行平稳、高频     

功率步进电机智能控制器——最佳驱动电路设计

本文针对目前国内功率步进电机应用中所存在的问题,通过讨论电机控制频率及驱动电路与电机输出力之间的关系,提出了一种能发挥最佳控制频率及具有优良的硬件电路性能的新型驱动器,从而使功率步进电机能有效地得到推广应用。     

建筑塔钟步进电机驱动电路

<正> 人们经常能见到一些高大建筑上设置有巨型建筑钟。以往,这些建筑钟多用步距角为180°的步进电机驱动。这种电机在来自电网及周围环境的干扰电磁脉冲的影响下,容易出现误触发而快走。其步距太大也会产生失步故障。解决上述问题的方法之一是采用小步距角高频率驱动的步进电机。本文介绍一种可驱动直径达5m的巨型建筑钟的电路。 一、电路原理 整机电原理图如图所示,全部电路由5块集成电路组成。其中IC1(CD4060)为带振荡电路的14级分频器,将晶振XT的4.194304MHz分频成256Hz的方波,由IC1③脚Q14端     

步进电机斩波驱动的研究

本文针对目前国内和我所的步进电机驱动线路中存在的功耗大、体积大等问题,通过对斩波驱动线路的试验、研究,使得功耗降低了两倍,带载启动频率提高了60％,体积大为减小。     

基于S7-200PLC实现步进电机的驱动控制

步进电机是一种将电脉冲信号转变为角位移或线位移的的执行元件。驱动步进电机的方法较多,本文旨在用S7-200PLC通过发送脉冲信号给步进电机的驱动器,由驱动器来驱动步进电机进行工作。本设计采用S7-200PLC和大功率晶体管实现对步进电机的驱动控制,硬件结构简单可靠,成本较低,实用性较强,具有良好的通用性和应用推广价值。     

晶体管音频放大器及展望

一场“数字”风暴正席卷家电产品的方方面面,成为人类生活变革的一种原动力。它提高了人们的生活质量,缩短了人与人之间的距离。在视听领域,“数字”也同样大显身手,音频信号放大器的数字化发展就是其中之一。一、模拟放大器长期以来,音响装置中的放大器大多属于线性放大器。按电路类别,可分为电压放大器(常称前级放大器)和功率放大器两大类。电压放大器用来放大比较微弱的信号,它的主要技术指标是电压增益;而功率放大器的主要作用是获得大的输出功率,要求它的输出电压和电流都有较大的幅度,其主要技术指标是最大输出功率。由于电压放大器的功率较小,且为单端放大电路,必须采用甲类放大电路;而功率放大器的功率消耗较大,为了节     

基亏步进电机的驱动系统及驱动接口的选择

步进电机又称为脉冲电机,是一种将电脉冲信号转化为相应角位移或线位移的执行元件。目前,步进电机广泛应用于工业自动控制、机器人、计算机外围设备等各种控制领域。本文主要对步进电机的驱动系统及驱动接口进行研究。     

超保真高性能双通道音频放大器LM1876

ＬＭ１８７６是双通道超保真音频放大器，每个通道可输出２０Ｗ功率，内部具有自动高温保护、低夺保护、过压保护等电路以及哑音和闲置等功能，其性能远超过其它同类产品，可广泛应用于各种立体声放大等场合。     

主扰回路对失配被扰回路的耦合效应

利用积分方法分析了主扰回路对失配被扰回路的耦合效应,得到了计算被扰回路耦合电压的一般公式,将积分方法的使用范围拓展到了高频范围,并用经典的耦合干扰分析方法进行了验证,得出Klewe理论和Jarvis模型得到的结果是此一般公式的特例.该公式在低频和高频条件下均适用,并能将传输线的反射,损耗,相移和平行长度不相等都考虑在内.     

利用升压三极管获取更多功率的方法

本设计实例采用的6L6束射功率管尽管已经存在了66年,现仍然十分流行地应用于电吉他放大器中,与其同类的6CA7(EL34)功率五极管也是高保真音响"发烧友"之所爱.     

Characterization of AMOLED pixel circuit without power line

We fabricated and evaluated the simple active matrix organic light emitting diode (AMOLED) pixel circuits without power line and proved that it is useful for the AMOLED display. Without power line in the pixel circuit we got higher-aperture ratio of emission area than the pixel with power line and the pixel with high aperture ratio can give a long life time due to lower current density of organic light emitting diode. However, the lack of power line requires the verification of the driving scheme of the pixel circuit. After fabrication of two types of AMOLED with and without power line in the pixel, we evaluated the pixel currents under various conditions. The operation of the pixel circuit without power line gave similar characteristics to that of the pixel circuit with power line. By the comparison, we verified that the pixel without power line is acceptable for the application to the AMOLED display combined with feedback compensation scheme for the uniform brightness.     

An integrated CMOS telephone line adapter

A novel fully CMOS circuit for electronic telephone line adaption is described. In the on-hook state the circuit operates in micropower condition, dissipates only 5 A, and is capable of generating the supply voltage required for retention of data stored on external RAM. In the off-hook state the circuit is boosted into the normal operation mode and is able to drive external bipolar transistors to synthesize the line impedance. The dc and the ac line impedances are set with external components, thus permitting the fulfillment of different PTT specifications. The circuit also performs line signal extraction and transmission, both for voice and DTMF. The dc line voltage is monitored, and a supervision block generates a precise reset signal when the line voltage drops out. The circuit has been integrated in a CMOS P-well 3-m double-poly single-metal technology; the silicon area is 6 mm².     

An integrated telephone speech circuit including a line fed loudspeaker amplifier

A new electronic speech circuit is described which replaces carbon microphone, hybrid transducer, sidetone network and click suppressor of the conventional telephone set. A low cost dynamic transducer is used instead of microphone and earphone. A low cost loudspeaker may also be used. The circuit is fed from DC line current by a special current source and contains a loudspeaker amplifier, other necessary amplifiers, a circuit for compensating line attenuation dependent on DC line current, and a stabilized DC voltage source, from which almost the whole DC line current may be drawn for other circuits too. Tone quality has been considerably improved in comparison with conventional telephone sets.     

Multichannel physiological monitor plus simultaneous full-duplexspeech channel using a dial-up telephone line

Because of bandwidth limitations, the Public Switched Telephone Network (PSTN) cannot normally accommodate simultaneous multichannel physiological signaling with speech. This communication describes work carried out to build a physiological monitoring system which can transmit up to six low-frequency data channels in the presence of a full-duplex speech channel using one telephone line.     

Extraction of power line maps from millimeter-wave polarimetric SARimages

Radar backscatter of power lines has lower values than those of the surrounding ground clutter when the power line is oriented at an off-normal direction with respect to the radar line of sight. For power lines, the traditional detection algorithms that are commonly based on the statistics of the backscatter power of the clutter and target result in excessive false-alarm rates due to very low signal-to-clutter ratio. The application of a statistical polarimetric detection algorithm that significantly improves the signal-to-clutter ratio is demonstrated. The coherence between the co- and cross-polarized backscatter components is used as the detection parameter. This statistical detection parameter can be applied to any extended targets such as a suspended cable in clutter background. Detection criteria based on clutter backscattering coefficients, power line size, and aspect angle, as well as the number of independent samples are obtained. The performance of the algorithm for mapping power lines in SAR images is demonstrated using a number of low-grazing incidence polarimetric SAR images at 35 GHz     

The stormproof power line

The forces of hurricanes, tornadoes, and typhoons exceed the energy of many thousands of atomic bombs. Only a fraction of this force, however, actually extends down to the earth's surface. A practical upper limit of maximum wind velocity at ground level due to storms is 200 mi/h (320 km/h). Most power lines ara built today to withstand less than that. Without increasing the amount of metal in the tower and thus the cost of material, it is possible to make the power line more wind resistant by applying streamlining concets to the design of the structural elements, including the conductors. There are several appraches to this problem that can be adapted to existing structures. A French patent suggests the use of a hose around an aerial conductor that turns to adjust its airfoil shape correctly to the prevailing wind. This is also adaptable to vertical members in the supporting tower. The proposed use of flaglike tapes or small fringed plastic threads that wrap around a conductor or angle iron to streamline it, regardless of wind direction, is another solution to this problem.