看明白场效应(ying)(ying)管应(ying)(ying)该如何检测维修-详解工作原理-KIA MOS管
信息来源：本站 日期(qi)：2018-08-04
场(chang)效(xiao)(xiao)应晶体(ti)(ti)管(guan)(guan)（Field Effect Transistor缩写(FET)）简称(cheng)(cheng)场(chang)效(xiao)(xiao)应管(guan)(guan)。主要有两种类型(xing)（junction FET—JFET)和金属 - 氧化物半导(dao)体(ti)(ti)场(chang)效(xiao)(xiao)应管(guan)(guan)（metal-oxide semiconductor FET，简称(cheng)(cheng)MOS-FET）。由多数载(zai)流(liu)子参与(yu)导(dao)电(dian)，也称(cheng)(cheng)为(wei)单极(ji)型(xing)晶体(ti)(ti)管(guan)(guan)。它属于电(dian)压(ya)控(kong)(kong)制(zhi)型(xing)半导(dao)体(ti)(ti)器件。具有输(shu)(shu)入电(dian)阻高（107～1015Ω）、噪声小(xiao)、功耗(hao)低、动态(tai)范围大、易于集(ji)成(cheng)、没(mei)有二次击穿现象、安全(quan)工作区域宽等(deng)优点，现已成(cheng)为(wei)双极(ji)型(xing)晶体(ti)(ti)管(guan)(guan)和功率晶体(ti)(ti)管(guan)(guan)的(de)(de)强(qiang)大竞争者。场(chang)效(xiao)(xiao)应管(guan)(guan)（FET）是利(li)用控(kong)(kong)制(zhi)输(shu)(shu)入回路的(de)(de)电(dian)场(chang)效(xiao)(xiao)应来控(kong)(kong)制(zhi)输(shu)(shu)出回路电(dian)流(liu)的(de)(de)一种半导(dao)体(ti)(ti)器件，并(bing)以此(ci)命名。由于它仅靠半导(dao)体(ti)(ti)中(zhong)的(de)(de)多数载(zai)流(liu)子导(dao)电(dian)，又称(cheng)(cheng)单极(ji)型(xing)晶体(ti)(ti)管(guan)(guan)。FET 英文(wen)为(wei)Field Effect Transistor，简写成(cheng)FET。
与双极型晶体(ti)管相比，场(chang)效应管具有如(ru)下特点(dian)。
（1）场效应管是(shi)电压控制器件(jian)，它通过VGS(栅源电压)来控制ID（漏极电流(liu)）；
（2）场效应管的控制输(shu)入端电流极小，因此它的输(shu)入电阻(zu)（107～1012Ω）很大。
（3）它是利用多数载流子(zi)导电，因此它的温度稳定(ding)性(xing)较(jiao)好；
（4）它组成的放大电路(lu)的电压放大系数要小(xiao)于三(san)极(ji)管(guan)组成放大电路(lu)的电压放大系数；
（5）场效应(ying)管的抗(kang)辐(fu)射能力强；
（6）由(you)于它不(bu)存(cun)在杂乱运动的(de)电子扩散引起(qi)的(de)散粒噪(zao)声(sheng)，所(suo)以噪(zao)声(sheng)低(di)。
场效应(ying)管工(gong)作原理用一句话说，就是“漏(lou)极(ji)(ji)(ji)(ji)-源(yuan)极(ji)(ji)(ji)(ji)间流经沟(gou)(gou)道(dao)的(de)ID，用以栅(zha)极(ji)(ji)(ji)(ji)与沟(gou)(gou)道(dao)间的(de)pn结形成的(de)反偏的(de)栅(zha)极(ji)(ji)(ji)(ji)电(dian)压控(kong)制ID”。更(geng)正确地说，ID流经通(tong)路的(de)宽度，即(ji)沟(gou)(gou)道(dao)截面(mian)积，它是由pn结反偏的(de)变化(hua)，产生耗尽层(ceng)(ceng)扩展(zhan)变化(hua)控(kong)制的(de)缘故。在(zai)VGS=0的(de)非饱和(he)区域，表(biao)示的(de)过(guo)(guo)渡层(ceng)(ceng)的(de)扩展(zhan)因(yin)为(wei)(wei)不(bu)很大，根据漏(lou)极(ji)(ji)(ji)(ji)-源(yuan)极(ji)(ji)(ji)(ji)间所加(jia)VDS的(de)电(dian)场，源(yuan)极(ji)(ji)(ji)(ji)区域的(de)某些电(dian)子被(bei)漏(lou)极(ji)(ji)(ji)(ji)拉去(qu)，即(ji)从漏(lou)极(ji)(ji)(ji)(ji)向源(yuan)极(ji)(ji)(ji)(ji)有电(dian)流ID流动。从门极(ji)(ji)(ji)(ji)向漏(lou)极(ji)(ji)(ji)(ji)扩展(zhan)的(de)过(guo)(guo)度层(ceng)(ceng)将(jiang)沟(gou)(gou)道(dao)的(de)一部(bu)分构(gou)成堵塞型(xing)，ID饱和(he)。将(jiang)这(zhei)种(zhong)状态称为(wei)(wei)夹(jia)断(duan)(duan)。这(zhei)意味着过(guo)(guo)渡层(ceng)(ceng)将(jiang)沟(gou)(gou)道(dao)的(de)一部(bu)分阻挡，并不(bu)是电(dian)流被(bei)切断(duan)(duan)。
在(zai)(zai)过(guo)渡(du)层由于(yu)没有电(dian)(dian)(dian)子(zi)、空穴的自由移动，在(zai)(zai)理想状态(tai)下几(ji)乎(hu)具有绝缘特性，通(tong)常电(dian)(dian)(dian)流也难(nan)流动。但是(shi)此时漏极(ji)(ji)(ji)-源(yuan)极(ji)(ji)(ji)间的电(dian)(dian)(dian)场，实(shi)际(ji)上是(shi)两个过(guo)渡(du)层接(jie)触(chu)漏极(ji)(ji)(ji)与门极(ji)(ji)(ji)下部附近(jin)(jin)，由于(yu)漂移电(dian)(dian)(dian)场拉去的高(gao)速电(dian)(dian)(dian)子(zi)通(tong)过(guo)过(guo)渡(du)层。因漂移电(dian)(dian)(dian)场的强度几(ji)乎(hu)不变产(chan)生ID的饱和现(xian)象。其次(ci)，VGS向(xiang)负的方向(xiang)变化，让VGS=VGS(off)，此时过(guo)渡(du)层大致成为覆盖全区域的状态(tai)。而(er)且(qie)VDS的电(dian)(dian)(dian)场大部分加到(dao)过(guo)渡(du)层上，将电(dian)(dian)(dian)子(zi)拉向(xiang)漂移方向(xiang)的电(dian)(dian)(dian)场，只(zhi)有靠近(jin)(jin)源(yuan)极(ji)(ji)(ji)的很短部分，这更使电(dian)(dian)(dian)流不能流通(tong)。
（一）MOS场效应管电源开(kai)关电路
MOS场(chang)效(xiao)(xiao)应(ying)(ying)(ying)管(guan)(guan)(guan)也被称为(wei)(wei)金属氧化物(wu)半导体场(chang)效(xiao)(xiao)应(ying)(ying)(ying)管(guan)(guan)(guan)(MetalOxideSemiconductor FieldEffect Transistor, MOSFET)。它一般有耗(hao)尽型(xing)和增(zeng)强(qiang)型(xing)两种。增(zeng)强(qiang)型(xing)MOS场(chang)效(xiao)(xiao)应(ying)(ying)(ying)管(guan)(guan)(guan)可分为(wei)(wei)NPN型(xing)PNP型(xing)。NPN型(xing)通常称为(wei)(wei)N沟道(dao)(dao)型(xing)，PNP型(xing)也叫P沟道(dao)(dao)型(xing)。对于N沟道(dao)(dao)的(de)场(chang)效(xiao)(xiao)应(ying)(ying)(ying)管(guan)(guan)(guan)其源(yuan)极(ji)和漏极(ji)接在N型(xing)半导体上，同(tong)样(yang)对于P沟道(dao)(dao)的(de)场(chang)效(xiao)(xiao)应(ying)(ying)(ying)管(guan)(guan)(guan)其源(yuan)极(ji)和漏极(ji)则接在P型(xing)半导体上。场(chang)效(xiao)(xiao)应(ying)(ying)(ying)管(guan)(guan)(guan)的(de)输(shu)(shu)(shu)出电(dian)(dian)(dian)流是由(you)输(shu)(shu)(shu)入(ru)的(de)电(dian)(dian)(dian)压（或称电(dian)(dian)(dian)场(chang)）控制，可以(yi)认为(wei)(wei)输(shu)(shu)(shu)入(ru)电(dian)(dian)(dian)流极(ji)小或没有输(shu)(shu)(shu)入(ru)电(dian)(dian)(dian)流，这使(shi)得该器件有很高的(de)输(shu)(shu)(shu)入(ru)阻抗，同(tong)时这也是我们称之为(wei)(wei)场(chang)效(xiao)(xiao)应(ying)(ying)(ying)管(guan)(guan)(guan)的(de)原因。
在二极(ji)(ji)(ji)管(guan)(guan)加(jia)上正(zheng)向电(dian)(dian)(dian)(dian)(dian)压(ya)（P端(duan)接(jie)(jie)正(zheng)极(ji)(ji)(ji)，N端(duan)接(jie)(jie)负(fu)极(ji)(ji)(ji)）时(shi)，二极(ji)(ji)(ji)管(guan)(guan)导(dao)(dao)通(tong)，其PN结(jie)有(you)(you)电(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)通(tong)过。这(zhei)是因为(wei)(wei)(wei)在P型(xing)(xing)(xing)(xing)半(ban)(ban)(ban)导(dao)(dao)体(ti)(ti)(ti)(ti)端(duan)为(wei)(wei)(wei)正(zheng)电(dian)(dian)(dian)(dian)(dian)压(ya)时(shi)，N型(xing)(xing)(xing)(xing)半(ban)(ban)(ban)导(dao)(dao)体(ti)(ti)(ti)(ti)内的(de)(de)(de)负(fu)电(dian)(dian)(dian)(dian)(dian)子(zi)被吸(xi)引而(er)(er)涌向加(jia)有(you)(you)正(zheng)电(dian)(dian)(dian)(dian)(dian)压(ya)的(de)(de)(de)P型(xing)(xing)(xing)(xing)半(ban)(ban)(ban)导(dao)(dao)体(ti)(ti)(ti)(ti)端(duan)，而(er)(er)P型(xing)(xing)(xing)(xing)半(ban)(ban)(ban)导(dao)(dao)体(ti)(ti)(ti)(ti)端(duan)内的(de)(de)(de)正(zheng)电(dian)(dian)(dian)(dian)(dian)子(zi)则(ze)朝N型(xing)(xing)(xing)(xing)半(ban)(ban)(ban)导(dao)(dao)体(ti)(ti)(ti)(ti)端(duan)运动(dong)，从(cong)而(er)(er)形(xing)成导(dao)(dao)通(tong)电(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)。同理(li)，当二极(ji)(ji)(ji)管(guan)(guan)加(jia)上反向电(dian)(dian)(dian)(dian)(dian)压(ya)（P端(duan)接(jie)(jie)负(fu)极(ji)(ji)(ji)，N端(duan)接(jie)(jie)正(zheng)极(ji)(ji)(ji)）时(shi)，这(zhei)时(shi)在P型(xing)(xing)(xing)(xing)半(ban)(ban)(ban)导(dao)(dao)体(ti)(ti)(ti)(ti)端(duan)为(wei)(wei)(wei)负(fu)电(dian)(dian)(dian)(dian)(dian)压(ya)，正(zheng)电(dian)(dian)(dian)(dian)(dian)子(zi)被聚(ju)(ju)集在P型(xing)(xing)(xing)(xing)半(ban)(ban)(ban)导(dao)(dao)体(ti)(ti)(ti)(ti)端(duan)，负(fu)电(dian)(dian)(dian)(dian)(dian)子(zi)则(ze)聚(ju)(ju)集在N型(xing)(xing)(xing)(xing)半(ban)(ban)(ban)导(dao)(dao)体(ti)(ti)(ti)(ti)端(duan)，电(dian)(dian)(dian)(dian)(dian)子(zi)不移动(dong)，其PN结(jie)没有(you)(you)电(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)通(tong)过，二极(ji)(ji)(ji)管(guan)(guan)截(jie)止。在栅(zha)极(ji)(ji)(ji)没有(you)(you)电(dian)(dian)(dian)(dian)(dian)压(ya)时(shi)，由(you)(you)前(qian)面分析(xi)可知，在源(yuan)极(ji)(ji)(ji)与漏(lou)(lou)(lou)极(ji)(ji)(ji)之(zhi)间(jian)(jian)不会有(you)(you)电(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)流(liu)(liu)(liu)过，此(ci)时(shi)场效应(ying)管(guan)(guan)处(chu)与截(jie)止状态（图7a）。当有(you)(you)一(yi)(yi)个(ge)正(zheng)电(dian)(dian)(dian)(dian)(dian)压(ya)加(jia)在N沟(gou)(gou)道的(de)(de)(de)MOS场效应(ying)管(guan)(guan)栅(zha)极(ji)(ji)(ji)上时(shi)，由(you)(you)于电(dian)(dian)(dian)(dian)(dian)场的(de)(de)(de)作用，此(ci)时(shi)N型(xing)(xing)(xing)(xing)半(ban)(ban)(ban)导(dao)(dao)体(ti)(ti)(ti)(ti)的(de)(de)(de)源(yuan)极(ji)(ji)(ji)和(he)漏(lou)(lou)(lou)极(ji)(ji)(ji)的(de)(de)(de)负(fu)电(dian)(dian)(dian)(dian)(dian)子(zi)被吸(xi)引出来而(er)(er)涌向栅(zha)极(ji)(ji)(ji)，但(dan)由(you)(you)于氧化膜的(de)(de)(de)阻挡，使得电(dian)(dian)(dian)(dian)(dian)子(zi)聚(ju)(ju)集在两个(ge)N沟(gou)(gou)道之(zhi)间(jian)(jian)的(de)(de)(de)P型(xing)(xing)(xing)(xing)半(ban)(ban)(ban)导(dao)(dao)中，从(cong)而(er)(er)形(xing)成电(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)，使源(yuan)极(ji)(ji)(ji)和(he)漏(lou)(lou)(lou)极(ji)(ji)(ji)之(zhi)间(jian)(jian)导(dao)(dao)通(tong)。可以想像(xiang)为(wei)(wei)(wei)两个(ge)N型(xing)(xing)(xing)(xing)半(ban)(ban)(ban)导(dao)(dao)体(ti)(ti)(ti)(ti)之(zhi)间(jian)(jian)为(wei)(wei)(wei)一(yi)(yi)条沟(gou)(gou)，栅(zha)极(ji)(ji)(ji)电(dian)(dian)(dian)(dian)(dian)压(ya)的(de)(de)(de)建(jian)立相(xiang)当于为(wei)(wei)(wei)它(ta)们之(zhi)间(jian)(jian)搭了一(yi)(yi)座(zuo)桥梁(liang)，该桥的(de)(de)(de)大(da)小由(you)(you)栅(zha)压(ya)的(de)(de)(de)大(da)小决定。
（二）C-MOS场(chang)效(xiao)应(ying)(ying)管（增强型(xing)MOS场(chang)效(xiao)应(ying)(ying)管）
电(dian)(dian)(dian)(dian)路将一(yi)个增强(qiang)型P沟(gou)道(dao)(dao)(dao)(dao)MOS场(chang)(chang)(chang)效(xiao)(xiao)应(ying)(ying)管(guan)和一(yi)个增强(qiang)型N沟(gou)道(dao)(dao)(dao)(dao)MOS场(chang)(chang)(chang)效(xiao)(xiao)应(ying)(ying)管(guan)组(zu)合在(zai)(zai)一(yi)起使用。当(dang)输入端(duan)为(wei)(wei)低电(dian)(dian)(dian)(dian)平(ping)时(shi)，P沟(gou)道(dao)(dao)(dao)(dao)MOS场(chang)(chang)(chang)效(xiao)(xiao)应(ying)(ying)管(guan)导通(tong)(tong)，输出端(duan)与(yu)电(dian)(dian)(dian)(dian)源正(zheng)极(ji)接(jie)通(tong)(tong)。当(dang)输入端(duan)为(wei)(wei)高(gao)电(dian)(dian)(dian)(dian)平(ping)时(shi)，N沟(gou)道(dao)(dao)(dao)(dao)MOS场(chang)(chang)(chang)效(xiao)(xiao)应(ying)(ying)管(guan)导通(tong)(tong)，输出端(duan)与(yu)电(dian)(dian)(dian)(dian)源地(di)接(jie)通(tong)(tong)。在(zai)(zai)该(gai)电(dian)(dian)(dian)(dian)路中，P沟(gou)道(dao)(dao)(dao)(dao)MOS场(chang)(chang)(chang)效(xiao)(xiao)应(ying)(ying)管(guan)和N沟(gou)道(dao)(dao)(dao)(dao)MOS场(chang)(chang)(chang)效(xiao)(xiao)应(ying)(ying)管(guan)总(zong)是(shi)在(zai)(zai)相(xiang)(xiang)反(fan)(fan)的(de)状态(tai)下工作，其(qi)相(xiang)(xiang)位输入端(duan)和输出端(duan)相(xiang)(xiang)反(fan)(fan)。通(tong)(tong)过这(zhei)种工作方(fang)式我们可以(yi)获得较大(da)的(de)电(dian)(dian)(dian)(dian)流输出。同时(shi)由于漏电(dian)(dian)(dian)(dian)流的(de)影响(xiang)，使得栅压在(zai)(zai)还没有到0V，通(tong)(tong)常在(zai)(zai)栅极(ji)电(dian)(dian)(dian)(dian)压小于1到2V时(shi)，MOS场(chang)(chang)(chang)效(xiao)(xiao)应(ying)(ying)管(guan)既(ji)被关断(duan)。不同场(chang)(chang)(chang)效(xiao)(xiao)应(ying)(ying)管(guan)其(qi)关断(duan)电(dian)(dian)(dian)(dian)压略有不同。也正(zheng)因(yin)为(wei)(wei)如此，使得该(gai)电(dian)(dian)(dian)(dian)路不会因(yin)为(wei)(wei)两管(guan)同时(shi)导通(tong)(tong)而造成电(dian)(dian)(dian)(dian)源短(duan)路。
测(ce)量(liang)(liang)场(chang)(chang)(chang)(chang)效应(ying)管(guan)的(de)好坏一(yi)般采用数(shu)(shu)字万用表的(de)二极管(guan)（蜂鸣(ming)挡）。测(ce)量(liang)(liang)前须将三只(zhi)(zhi)引(yin)脚短(duan)接放电(dian)，避免测(ce)量(liang)(liang)中(zhong)(zhong)发(fa)生误差(cha)。用两(liang)表笔任意触碰场(chang)(chang)(chang)(chang)效应(ying)管(guan)的(de)三只(zhi)(zhi)引(yin)脚中(zhong)(zhong)的(de)两(liang)只(zhi)(zhi)，好的(de)场(chang)(chang)(chang)(chang)效应(ying)管(guan)测(ce)量(liang)(liang)结果(guo)(guo)(guo)应(ying)只(zhi)(zhi)有(you)(you)一(yi)次有(you)(you)读数(shu)(shu)，并(bing)且在 400～800 之(zhi)间。如果(guo)(guo)(guo)在最终测(ce)量(liang)(liang)结果(guo)(guo)(guo)中(zhong)(zhong)测(ce)得只(zhi)(zhi)有(you)(you)一(yi)次有(you)(you)读数(shu)(shu)，并(bing)且为(wei)(wei)“0”时，或者测(ce)量(liang)(liang)结果(guo)(guo)(guo)中(zhong)(zhong)有(you)(you)两(liang)次读数(shu)(shu)，须用小镊子短(duan)接该组引(yin)脚重新(xin)进行测(ce)量(liang)(liang)。如果(guo)(guo)(guo)重测(ce)后阻值在 400～800 之(zhi)间说明场(chang)(chang)(chang)(chang)效应(ying)管(guan)正(zheng)常。如果(guo)(guo)(guo)其中(zhong)(zhong)有(you)(you)一(yi)组数(shu)(shu)据为(wei)(wei)0，则场(chang)(chang)(chang)(chang)效应(ying)管(guan)已经被击(ji)穿。
场效应管的检(jian)测(ce)步骤(zhou)如下(xia)：
（1）首先观(guan)察待测(ce)场效(xiao)应管(guan)外观(guan)，看(kan)待测(ce)场效(xiao)应管(guan)是否完好，如果存(cun)在烧焦或针脚断裂等情况说明(ming)场(chang)效应管已发生损(sun)坏，如图1所示，本次(ci)待测(ce)的场(chang)效应管外型完好(hao)没(mei)有明(ming)显(xian)的物理损(sun)坏。
（2）待测(ce)场(chang)效应管外型完好没有(you)明(ming)显损坏(huai)需进一步进行测(ce)量，用一小镊子夹住待测(ce)场(chang)效(xiao)应(ying)管用热风(feng)焊台将(jiang)待测场效(xiao)应(ying)管焊下(xia)。
（3）将(jiang)场效(xiao)应管(guan)从主板中卸下后，须用小刻刀清(qing)洁(jie)待(dai)测场效(xiao)应管(guan)的(de)引(yin)脚(jiao)，如(ru)图2所示。去(qu)除引(yin)脚(jiao)上的(de)污物，避免(mian)因油污的(de)隔离(li)作(zuo)用影响测量时的(de)准确(que)性。
（4）清洁完成(cheng)后，用小镊子(zi)对(dui)待侧场效应(ying)管进行放电(dian)避(bi)免残留电(dian)荷对(dui)检测的影响（场效应管极(ji)易存储电荷）如(ru)图3所示。
（5）选(xuan)择(ze)数(shu)字万(wan)用(yong)表的 “二极(ji)管”挡，如图4所(suo)示。
（6）将(jiang)黑表(biao)笔接待测(ce)场效应管左边(bian)的第(di)一只(zhi)引(yin)脚(jiao)，用(yong)红表(biao)笔分别去测(ce)与另外两(liang)只(zhi)引(yin)脚(jiao)间的阻值，如图5所示。两次检测均为(wei)无(wu)穷大。
（7）将黑(hei)表笔接中间(jian)(jian)的(de)引(yin)脚，用红表笔分别去测与另(ling)外两只引(yin)脚间(jian)(jian)的(de)阻值，如图6所示。
（8）将黑表笔(bi)接在第三(san)只引脚(jiao)上，用红(hong)笔(bi)笔(bi)分别去(qu)测另外两(liang)只引脚(jiao)与(yu)该引脚(jiao)间的阻值如图7所(suo)示。
（9）由于测量的(de)(de)(de)场(chang)(chang)效应管的(de)(de)(de)三只引脚中的(de)(de)(de)任意两(liang)只引脚的(de)(de)(de)阻(zu)值(zhi)，只有(you)一次有(you)读（540），且(qie)阻(zu)值(zhi)在(zai) 400～800 之间，因此判断此场(chang)(chang)效应管正常。
联系(xi)方(fang)式(shi)：邹先生(sheng)
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