什么是耦合,耦合电容

什么是耦合,耦合电容 耦合指信号由第一级向第二级传递的过程，一般不加注明时往往是指交流耦合。退耦是指对电源采取进一步的滤波措施，去除两级间信号通过电源互相干扰的影响。耦合常数是指耦合电容值与第二级输入阻抗值乘积对应的时间常数。 退耦有三个目的:1.将电源中的高频纹波去除，将多级放大器的高频信号通过电源相互串扰的通路切断;2.大信号工作时，电路对电源需求加大，引起电源波动，通过退耦降低大信号时电源波动对输入级/高电压增益级的影响;3.形成悬浮地或是悬浮电源，在复杂的系统中完成各部分地线或是电源的协调匹配。 1，耦合，有联系的意思。 2，耦合元件，尤其是指使输入输出产生联系的元件。 3，去耦合元件，指消除信号联系的元件。 4，去耦合电容简称去耦电容。 5，例如，晶体管放大器发射极有一个自给偏压电阻，它同时又使信号产生压降反馈到输入端形成了输入输出信号耦合，这个电阻就是产生了耦合的元件，如果在这个电阻两端并联一个电容，由于适当容量的电容器对交流信号较小的阻抗(这需要计算)这样就减小了电阻产生的耦合效应，故称此电容为去耦电容。 有源器件在开关时产生的高频开关噪声将沿着电源线传播。去耦电容的主要功能就是提供一个局部的直流电源给有源器件，以减少开关噪声在板上的传播和将噪声引导到地。 摘引自伦德全《电路板级的电磁兼容设计》一文，该论文对噪声耦和路径、去耦电容和旁路电容的使用都讲得不错。请参阅。 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 干扰的耦合方式 to West rear, to County Shen Liqun report guerrillas breakout Hou of action situation, boat via Zhejiang wuxing daughter town Shi, six people has a NI surname "spies" (enemy) midway tuogu landing tipsters, away from small town three in Xu, was day Elves Li Taishan Department captured, five people all killed, broken corpse sank Yu River in the. On January 18, 1943, when the Japanese army militiamen arrested 53 people in Wuzhen, transferred to the tomb of the former Japanese military police command (in the "Tai" Jiang Yuan), the 28th in Shenyang North of jade bang massacred them. Hu Maosheng knife wounds woke up in the middle of them, crawling out from the dead, in the tomb of Gao Changhai residents, saved by bing. Such as Hu Maosheng, Gao Changhai is a witness to this tragedy. (B) in memory of "massacre" Xu Youyong yan tomb is the copper law. Copper originally was called Luo yan Tomb, because Eastern Han dynasty distinguished prose poems my father yan Tan bogey was buried in the town's water. Has a long history here, cultural atmosphere, and there are many old houses, and left many people with lofty ideals. Business flourished here, is the hub of four townships of agricultural and sideline products, wine culture has a long history. The outskirts of the town has left, "Huang Chi", originally Yue water hides 干扰源产生的干扰信号是通过一定的耦合通道对电控系统发生电磁干扰作用的。干扰的耦合方式无非是通过导线、空间、公共线等作用在电控系统上。分析下来主要有以下几种。 直接耦合:这是干扰侵入最直接的方式，也是系统中存在最普遍的一种方式。如干扰信号通过导线直接侵入系统而造成对系统的干扰。对这种耦合方式，可采用滤波去耦的方法有效地抑制电磁干扰信号的传入。 公共阻抗耦合:这也是常见的一种耦合方式。常发生在两个电路的电流有共同通路的情况。公共阻抗耦合有公共地和电源阻抗两种。防止这种耦合应使耦合阻抗趋近于零、使干扰源和被干扰对象间没有公共阻抗。 电容耦合:又称电场耦合或静电耦合，是由于分布电容的存在而产生的一种耦合方式。 电磁感应耦合:又称磁场耦合。是由于内部或外部空间电磁场感应的一种耦合方式，防止这种耦合的常用方法是对容易受干扰的器件或电路加以屏蔽。 辐射耦合:电磁场的辐射也会造成干扰耦合，是一种无规则的干扰。这种干扰很容易通过电源线传到系统中去。另当信号传输线较长时，它们能辐射干扰波和接收干扰波，称为大线效应。 漏电耦合:所谓漏电耦合就是电阻性耦合。这种干扰常在绝缘降低时发生。 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ to West rear, to County Shen Liqun report guerrillas breakout Hou of action situation, boat via Zhejiang wuxing daughter town Shi, six people has a NI surname "spies" (enemy) midway tuogu landing tipsters, away from small town three in Xu, was day Elves Li Taishan Department captured, five people all killed, broken corpse sank Yu River in the. On January 18, 1943, when the Japanese army militiamen arrested 53 people in Wuzhen, transferred to the tomb of the former Japanese military police command (in the "Tai" Jiang Yuan), the 28th in Shenyang North of jade bang massacred them. Hu Maosheng knife wounds woke up in the middle of them, crawling out from the dead, in the tomb of Gao Changhai residents, saved by bing. Such as Hu Maosheng, Gao Changhai is a witness to this tragedy. (B) in memory of "massacre" Xu Youyong yan tomb is the copper law. Copper originally was called Luo yan Tomb, because Eastern Han dynasty distinguished prose poems my father yan Tan bogey was buried in the town's water. Has a long history here, cultural atmosphere, and there are many old houses, and left many people with lofty ideals. Business flourished here, is the hub of four townships of agricultural and sideline products, wine culture has a long history. The outskirts of the town has left, "Huang Chi", originally Yue water hides 记得以前我的观点是:去藕电容一般容量比较大，也就是避免噪声耦合到其他部分的意思;旁路电容容量小，提供低阻抗的噪声回流路径。 其实这种说法也可以算没有什么大错误。但是经过偶查阅了相关资料，才发现其实decouple和bypass从根本上来说没有任何区别，两者在称谓上可以互换。两者的作用低俗一点说:当电源用。所谓噪声其实就是电源的波动，电源波动来自于两个方面:电源本身的波动，负载对电流需求变化和电源系统相应能力的差别带来的电压波动。而去藕和旁路电容都是相对负载变化引起的噪声来说。所以他们两个没有必要做区分。而且实际上电容值的大小，数量也是有理论根据可循的，如果随意选择，可能会在某些情况下遇到去藕电容(旁路)和分布参数发生自激振荡的情况。所以真正意义上的去藕和旁路都是根据负载和供电系统的实际情况来说的。没有必要去做区分，也没有本质区别。 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 电容是板卡设计中必用的元件，其品质的好坏已经成为我们判断板卡质量的一个很重要的方面。 ?电容的功能和示方法。 由两个金属极，中间夹有绝缘介质构成。电容的特性主要是隔直流通交流，因此多用于级间耦合、滤波、去耦、旁路及信号调谐。电容在电路中用“C”加数字表示，比如C8，表示在电路中编号为8的电容。 ?电容的分类。 电容按介质不同分为:气体介质电容，液体介质电容，无机固体介质电容，有机固体介质电容电解电容。按极性分为:有极性电容和无极性电容。按结构可分为:固定电容，可变电容，微调电容。 ?电容的容量。 电容容量表示能贮存电能的大小。电容对交流信号的阻碍作用称为容抗，容抗与交流信号的频率和电容量有关，容抗XC=1/2πf c (f表示交流信号的频率，Cto West rear, to County Shen Liqun report guerrillas breakout Hou of action situation, boat via Zhejiang wuxing daughter town Shi, six people has a NI surname "spies" (enemy) midway tuogu landing tipsters, away from small town three in Xu, was day Elves Li Taishan Department captured, five people all killed, broken corpse sank Yu River in the. On January 18, 1943, when the Japanese army militiamen arrested 53 people in Wuzhen, transferred to the tomb of the former Japanese military police command (in the "Tai" Jiang Yuan), the 28th in Shenyang North of jade bang massacred them. Hu Maosheng knife wounds woke up in the middle of them, crawling out from the dead, in the tomb of Gao Changhai residents, saved by bing. Such as Hu Maosheng, Gao Changhai is a witness to this tragedy. (B) in memory of "massacre" Xu Youyong yan tomb is the copper law. Copper originally was called Luo yan Tomb, because Eastern Han dynasty distinguished prose poems my father yan Tan bogey was buried in the town's water. Has a long history here, cultural atmosphere, and there are many old houses, and left many people with lofty ideals. Business flourished here, is the hub of four townships of agricultural and sideline products, wine culture has a long history. The outskirts of the town has left, "Huang Chi", originally Yue water hides 表示电容容量)。 ?电容的容量单位和耐压。 电容的基本单位是F(法)，其它单位还有:毫法(mF)、微法(uF)、纳法(nF)、皮法(pF)。由于单位F 的容量太大，所以我们看到的一般都是μF、nF、pF的单位。换算关系:1F,1000000μF，1μF=1000nF=1000000pF。 每一个电容都有它的耐压值，用V表示。一般无极电容的标称耐压值比较高有:63V、100V、160V、250V、400V、600V、1000V等。有极电容的耐压相对比较低，一般标称耐压值有:4V、6.3V、10V、16V、25V、35V、50V、63V、80V、100V、220V、400V等。 ?电容的标注方法和容量误差。 电容的标注方法分为:直标法、色标法和数标法。对于体积比较大的电容，多采用直标法。如果是0.005，表示0.005uF=5nF。如果是5n，那就表示的是5nF。 数标法:一般用三位数字表示容量大小，前两位表示有效数字，第三位数字是10的多少次方。如:102表示10x10x10 PF=1000PF，203表示20x10x10x10 PF。 色标法，沿电容引线方向，用不同的颜色表示不同的数字，第一、二种环表示电容量，第三种颜色表示有效数字后零的个数(单位为pF)。颜色代表的数值为:黑=0、棕=1、红=2、橙=3、黄=4、绿=5、蓝=6、紫=7、灰=8、白=9。 电容容量误差用符号F、G、J、K、L、M来表示，允许误差分别对应为?1%、?2%、?5%、?10%、?15%、?20%。 ?电容的正负极区分和测量。 电容上面有标志的黑块为负极。在PCB上电容位置上有两个半圆，涂颜色的半圆对应的引脚为负极。也有用引脚长短来区别正负极长脚为正，短脚为负。 当我们不知道电容的正负极时，可以用万用表来测量。电容两极之间的介质并不是绝对的绝缘体，它的电阻也不是无限大，而是一个有限的数值，一般在1000兆欧以上。电容两极之间的电阻叫做绝缘电阻或漏电电阻。只有电解电容的正极to West rear, to County Shen Liqun report guerrillas breakout Hou of action situation, boat via Zhejiang wuxing daughter town Shi, six people has a NI surname "spies" (enemy) midway tuogu landing tipsters, away from small town three in Xu, was day Elves Li Taishan Department captured, five people all killed, broken corpse sank Yu River in the. On January 18, 1943, when the Japanese army militiamen arrested 53 people in Wuzhen, transferred to the tomb of the former Japanese military police command (in the "Tai" Jiang Yuan), the 28th in Shenyang North of jade bang massacred them. Hu Maosheng knife wounds woke up in the middle of them, crawling out from the dead, in the tomb of Gao Changhai residents, saved by bing. Such as Hu Maosheng, Gao Changhai is a witness to this tragedy. (B) in memory of "massacre" Xu Youyong yan tomb is the copper law. Copper originally was called Luo yan Tomb, because Eastern Han dynasty distinguished prose poems my father yan Tan bogey was buried in the town's water. Has a long history here, cultural atmosphere, and there are many old houses, and left many people with lofty ideals. Business flourished here, is the hub of four townships of agricultural and sideline products, wine culture has a long history. The outskirts of the town has left, "Huang Chi", originally Yue water hides 接电源正(电阻挡时的黑表笔)，负端接电源负(电阻挡时的红表笔)时，电解电容的漏电流才小(漏电阻大)。反之，则电解电容的漏电流增加(漏电阻减小)。这样，我们先假定某极为“+”极，万用表选用R*100或R*1K挡，然后将假定的“+”极与万用表的黑表笔相接，另一电极与万用表的红表笔相接，记下表针停止的刻度(表针靠左阻值大)，对于数字万用表来说可以直接读出读数。然后将电容放电(两根引线碰一下)，然后两只表笔对调，重新进行测量。两次测量中，表针最后停留的位置靠左(或阻值大)的那次，黑表笔接的就是电解电容的正极。 ?电容使用的一些经验及来四个误区。 一些经验:在电路中不能确定线路的极性时，建议使用无极电解电容。通过电解电容的纹波电流不能超过其充许范围。如超过了值，需选用耐大纹波电流的电容。电容的工作电压不能超过其额定电压。在进行电容的焊接的时候，电烙铁应与电容的塑料外壳保持一定的距离，以防止过热造成塑料套管破裂。并且焊接时间不应超过10秒，焊接温度不应超过260摄氏度。 四个误区: ?电容容量越大越好。 很多人在电容的替换中往往爱用大容量的电容。我们知道虽然电容越大，为IC提供的电流补偿的能力越强。且不说电容容量的增大带来的体积变大，增加成本的同时还影响空气流动和散热。关键在于电容上存在寄生电感，电容放电回路会在某个频点上发生谐振。在谐振点，电容的阻抗小。因此放电回路的阻抗最小，补充能量的效果也最好。但当频率超过谐振点时，放电回路的阻抗开始增加，电容提供电流能力便开始下降。电容的容值越大，谐振频率越低，电容能有效补偿电流的频率范围也越小。从保证电容提供高频电流的能力的角度来说，电容越大越好的观点是错误的，一般的电路设计中都有一个参考值的。 to West rear, to County Shen Liqun report guerrillas breakout Hou of action situation, boat via Zhejiang wuxing daughter town Shi, six people has a NI surname "spies" (enemy) midway tuogu landing tipsters, away from small town three in Xu, was day Elves Li Taishan Department captured, five people all killed, broken corpse sank Yu River in the. On January 18, 1943, when the Japanese army militiamen arrested 53 people in Wuzhen, transferred to the tomb of the former Japanese military police command (in the "Tai" Jiang Yuan), the 28th in Shenyang North of jade bang massacred them. Hu Maosheng knife wounds woke up in the middle of them, crawling out from the dead, in the tomb of Gao Changhai residents, saved by bing. Such as Hu Maosheng, Gao Changhai is a witness to this tragedy. (B) in memory of "massacre" Xu Youyong yan tomb is the copper law. Copper originally was called Luo yan Tomb, because Eastern Han dynasty distinguished prose poems my father yan Tan bogey was buried in the town's water. Has a long history here, cultural atmosphere, and there are many old houses, and left many people with lofty ideals. Business flourished here, is the hub of four townships of agricultural and sideline products, wine culture has a long history. The outskirts of the town has left, "Huang Chi", originally Yue water hides ?同样容量的电容，并联越多的小电容越好， 耐压值、耐温值、容值、ESR(等效电阻)等是电容的几个重要参数，对于ESR自然是越低越好。ESR与电容的容量、频率、电压、温度等都有关系。当电压固定时候，容量越大，ESR越低。在板卡设计中采用多个小电容并连多是出与PCB空间的限制，这样有的人就认为，越多的并联小电阻，ESR越低，效果越好。理论上是如此，但是要考虑到电容接脚焊点的阻抗，采用多个小电容并联，效果并不一定突出。 ?ESR越低，效果越好。 结合我们上面的提高的供电电路来说，对于输入电容来说，输入电容的容量要大一点。相对容量的要求，对ESR的要求可以适当的降低。因为输入电容主要是耐压，其次是吸收MOSFET的开关脉冲。对于输出电容来说，耐压的要求和容量可以适当的降低一点。ESR的要求则高一点，因为这里要保证的是足够的电流通过量。但这里要注意的是ESR并不是越低越好，低ESR电容会引起开关电路振荡。而消振电路复杂同时会导致成本的增加。板卡设计中，这里一般有一个参考值，此作为元件选用参数，避免消振电路而导致成本的增加。 ?好电容代表着高品质。 “唯电容论”曾经盛极一时，一些厂商和媒体也刻意的把这个事情做成一个卖点。在板卡设计中，电路设计水平是关键。和有的厂商可以用两相供电做出比一些厂商采用四相供电更稳定的产品一样，一味的采用高价电容，不一定能做出好产品。衡量一个产品，一定要全方位多角度的去考虑，切不可把电容的作用有意无意的夸大. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 滤波电容,是用来平滑电压的,去藕电容是用来去藕的撒,还有那个旁路就是用来给交流电压短路的. to West rear, to County Shen Liqun report guerrillas breakout Hou of action situation, boat via Zhejiang wuxing daughter town Shi, six people has a NI surname "spies" (enemy) midway tuogu landing tipsters, away from small town three in Xu, was day Elves Li Taishan Department captured, five people all killed, broken corpse sank Yu River in the. On January 18, 1943, when the Japanese army militiamen arrested 53 people in Wuzhen, transferred to the tomb of the former Japanese military police command (in the "Tai" Jiang Yuan), the 28th in Shenyang North of jade bang massacred them. Hu Maosheng knife wounds woke up in the middle of them, crawling out from the dead, in the tomb of Gao Changhai residents, saved by bing. Such as Hu Maosheng, Gao Changhai is a witness to this tragedy. (B) in memory of "massacre" Xu Youyong yan tomb is the copper law. Copper originally was called Luo yan Tomb, because Eastern Han dynasty distinguished prose poems my father yan Tan bogey was buried in the town's water. Has a long history here, cultural atmosphere, and there are many old houses, and left many people with lofty ideals. Business flourished here, is the hub of four townships of agricultural and sideline products, wine culture has a long history. The outskirts of the town has left, "Huang Chi", originally Yue water hides 回答者:zz175 - 见习魔法师 二级 4-7 13:59 滤波电容用在电源上，使电源更平滑，没有杂波; 去耦电容用在直流信号反馈上，去掉交流耦合信号; 旁路电容用在直流通路连接时提高交流信号通过率的。 回答者:hwdz - 助理 二级 4-7 14:10 滤波电容用在电源整流电路中，用来滤除交流成分。使输出的直流更平滑。 去耦电容用在放大电路中不需要交流的地方，用来消除自激，使放大器稳定工作。 旁路电容用在有电阻连接时，接在电阻两端使交流信号顺利通过 to West rear, to County Shen Liqun report guerrillas breakout Hou of action situation, boat via Zhejiang wuxing daughter town Shi, six people has a NI surname "spies" (enemy) midway tuogu landing tipsters, away from small town three in Xu, was day Elves Li Taishan Department captured, five people all killed, broken corpse sank Yu River in the. On January 18, 1943, when the Japanese army militiamen arrested 53 people in Wuzhen, transferred to the tomb of the former Japanese military police command (in the "Tai" Jiang Yuan), the 28th in Shenyang North of jade bang massacred them. Hu Maosheng knife wounds woke up in the middle of them, crawling out from the dead, in the tomb of Gao Changhai residents, saved by bing. Such as Hu Maosheng, Gao Changhai is a witness to this tragedy. (B) in memory of "massacre" Xu Youyong yan tomb is the copper law. Copper originally was called Luo yan Tomb, because Eastern Han dynasty distinguished prose poems my father yan Tan bogey was buried in the town's water. Has a long history here, cultural atmosphere, and there are many old houses, and left many people with lofty ideals. Business flourished here, is the hub of four townships of agricultural and sideline products, wine culture has a long history. The outskirts of the town has left, "Huang Chi", originally Yue water hides