场效应晶体管工作(zuo)原理(li)图(tu)文详解及引脚、参数等介绍-KIA MOS管
信息来源：本站 日期：2018-08-16
场效应(ying)(ying)晶体(ti)管(guan)（Field Effect Transistor缩(suo)写(FET)）简(jian)称(cheng)场效应(ying)(ying)管(guan)。主要有(you)两种类型（junction FET—JFET)和金属(shu) - 氧化物半导(dao)体(ti)场效应(ying)(ying)管(guan)（metal-oxide semiconductor FET，简(jian)称(cheng)MOS-FET）。由(you)多数载流子参与导(dao)电(dian)，也称(cheng)为单极型晶体(ti)管(guan)。它属(shu)于电(dian)压控制型半导(dao)体(ti)器件。具有(you)输入电(dian)阻高（107～1015Ω）、噪声小、功(gong)耗低(di)、动态范围大、易(yi)于集成(cheng)、没(mei)有(you)二次击(ji)穿现象、安全工作区域宽等优点(dian)，现已(yi)成(cheng)为双极型晶体(ti)管(guan)和功(gong)率晶体(ti)管(guan)的强大竞争者。
场效应晶体(ti)(ti)管（FET）是(shi)利用控制输(shu)入回(hui)路的(de)电(dian)场效应来控制输(shu)出回(hui)路电(dian)流(liu)的(de)一种半导(dao)(dao)体(ti)(ti)器(qi)件(jian)，并以此命名。由(you)于它仅靠半导(dao)(dao)体(ti)(ti)中的(de)多数(shu)载流(liu)子导(dao)(dao)电(dian)，又称单极型晶体(ti)(ti)管。FET 英文(wen)为Field Effect Transistor，简写成(cheng)FET。
一：场效应晶体(ti)管是电(dian)压掌握机件，它经(jing)过(guo)VGS（栅源电(dian)压）来掌握ID（漏极直流电(dian)）；
二：场效(xiao)应晶体管的输出(chu)端(duan)直(zhi)流(liu)电极(ji)小，因而它的输出(chu)电阻(zu)很大。
三：它是应(ying)用少数载(zai)流子导热，因而它的量度(du)稳固性(xing)较好；
四：它组成(cheng)的缩小(xiao)(xiao)通路(lu)的电(dian)缩小(xiao)(xiao)小(xiao)(xiao)系数(shu)要小(xiao)(xiao)于三(san)极管组成(cheng)缩小(xiao)(xiao)通路(lu)的电(dian)缩小(xiao)(xiao)小(xiao)(xiao)系数(shu)；
五：场效应(ying)晶体(ti)管的抗辐照(zhao)威力强；
六：因为没(mei)有(you)具(ju)有(you)错杂活(huo)动的(de)少子(zi)分(fen)散惹起的(de)散粒噪(zao)音，因为噪(zao)音低。
场(chang)(chang)效应(ying)(ying)晶体(ti)(ti)管，其内部(bu)结构(gou)见图(tu)1。它可分为NPN型PNP型。NPN型通常称(cheng)为N沟道(dao)(dao)型，PNP型也叫P沟道(dao)(dao)型。由(you)图(tu)可看(kan)出，对(dui)于(yu)N沟道(dao)(dao)的(de)(de)场(chang)(chang)效应(ying)(ying)管其源极(ji)(ji)和漏极(ji)(ji)接(jie)在(zai)N型半导体(ti)(ti)上，同样对(dui)于(yu)P沟道(dao)(dao)的(de)(de)场(chang)(chang)效应(ying)(ying)管其源极(ji)(ji)和漏极(ji)(ji)则(ze)接(jie)在(zai)P型半导体(ti)(ti)上。我们知道(dao)(dao)一般(ban)三极(ji)(ji)管是由(you)输(shu)入的(de)(de)电(dian)(dian)流(liu)控制输(shu)出的(de)(de)电(dian)(dian)流(liu)。但对(dui)于(yu)场(chang)(chang)效应(ying)(ying)管，其输(shu)出电(dian)(dian)流(liu)是由(you)输(shu)入的(de)(de)电(dian)(dian)压（或称(cheng)电(dian)(dian)场(chang)(chang)）控制，可以认(ren)为输(shu)入电(dian)(dian)流(liu)极(ji)(ji)小或没有输(shu)入电(dian)(dian)流(liu)，这使得该器(qi)件有很高的(de)(de)输(shu)入阻抗，同时这也是我们称(cheng)之(zhi)为场(chang)(chang)效应(ying)(ying)管的(de)(de)原因。
图(tu)1
为解(jie)释MOS场效应管(guan)(guan)(guan)工作原理图，我(wo)们先(xian)了解(jie)一(yi)下仅(jin)含有(you)一(yi)个(ge)P—N结的二(er)(er)极(ji)管(guan)(guan)(guan)的工作过(guo)程。如图2所示，我(wo)们知道在(zai)二(er)(er)极(ji)管(guan)(guan)(guan)加上正(zheng)向(xiang)(xiang)电(dian)压(ya)(ya)（P端(duan)(duan)(duan)接正(zheng)极(ji)，N端(duan)(duan)(duan)接负(fu)(fu)极(ji)）时，二(er)(er)极(ji)管(guan)(guan)(guan)导(dao)(dao)通(tong)，其PN结有(you)电(dian)流(liu)(liu)通(tong)过(guo)。这是因(yin)为在(zai)P型(xing)半(ban)导(dao)(dao)体(ti)(ti)(ti)(ti)端(duan)(duan)(duan)为正(zheng)电(dian)压(ya)(ya)时，N型(xing)半(ban)导(dao)(dao)体(ti)(ti)(ti)(ti)内(nei)的负(fu)(fu)电(dian)子(zi)被吸引而(er)(er)涌向(xiang)(xiang)加有(you)正(zheng)电(dian)压(ya)(ya)的P型(xing)半(ban)导(dao)(dao)体(ti)(ti)(ti)(ti)端(duan)(duan)(duan)，而(er)(er)P型(xing)半(ban)导(dao)(dao)体(ti)(ti)(ti)(ti)端(duan)(duan)(duan)内(nei)的正(zheng)电(dian)子(zi)则(ze)朝N型(xing)半(ban)导(dao)(dao)体(ti)(ti)(ti)(ti)端(duan)(duan)(duan)运动(dong)，从而(er)(er)形成导(dao)(dao)通(tong)电(dian)流(liu)(liu)。同理，当(dang)二(er)(er)极(ji)管(guan)(guan)(guan)加上反向(xiang)(xiang)电(dian)压(ya)(ya)（P端(duan)(duan)(duan)接负(fu)(fu)极(ji)，N端(duan)(duan)(duan)接正(zheng)极(ji)）时，这时在(zai)P型(xing)半(ban)导(dao)(dao)体(ti)(ti)(ti)(ti)端(duan)(duan)(duan)为负(fu)(fu)电(dian)压(ya)(ya)，正(zheng)电(dian)子(zi)被聚集在(zai)P型(xing)半(ban)导(dao)(dao)体(ti)(ti)(ti)(ti)端(duan)(duan)(duan)，负(fu)(fu)电(dian)子(zi)则(ze)聚集在(zai)N型(xing)半(ban)导(dao)(dao)体(ti)(ti)(ti)(ti)端(duan)(duan)(duan)，电(dian)子(zi)不(bu)移(yi)动(dong)，其PN结没有(you)电(dian)流(liu)(liu)通(tong)过(guo)，二(er)(er)极(ji)管(guan)(guan)(guan)截(jie)止(zhi)。
图2
对于场效(xiao)应(ying)(ying)管，在(zai)栅极没有电(dian)压(ya)时，由前面(mian)分析可(ke)知(zhi)，在(zai)源(yuan)极与漏(lou)极之(zhi)间不会有电(dian)流流过，此(ci)时场效(xiao)应(ying)(ying)管处与截(jie)止状(zhuang)态。当(dang)有一个正电(dian)压(ya)加在(zai)N沟道MOS。
下(xia)(xia)面简述一下(xia)(xia)用C-MOS场(chang)(chang)效(xiao)应(ying)(ying)(ying)管（增(zeng)强型(xing)MOS场(chang)(chang)效(xiao)应(ying)(ying)(ying)管）组(zu)成(cheng)的应(ying)(ying)(ying)用电(dian)(dian)路(lu)的工作(zuo)过程，就爱见图3。电(dian)(dian)路(lu)将(jiang)一个增(zeng)强型(xing)P沟(gou)(gou)道(dao)(dao)(dao)(dao)MOS场(chang)(chang)效(xiao)应(ying)(ying)(ying)管和一个增(zeng)强型(xing)N沟(gou)(gou)道(dao)(dao)(dao)(dao)MOS场(chang)(chang)效(xiao)应(ying)(ying)(ying)管组(zu)合在一起使用。当输入端(duan)(duan)(duan)为(wei)低电(dian)(dian)平时，P沟(gou)(gou)道(dao)(dao)(dao)(dao)MOS场(chang)(chang)效(xiao)应(ying)(ying)(ying)管导(dao)通(tong)，输出端(duan)(duan)(duan)与电(dian)(dian)源正极(ji)接(jie)(jie)通(tong)。当输入端(duan)(duan)(duan)为(wei)高(gao)电(dian)(dian)平时，N沟(gou)(gou)道(dao)(dao)(dao)(dao)MOS场(chang)(chang)效(xiao)应(ying)(ying)(ying)管导(dao)通(tong)，输出端(duan)(duan)(duan)与电(dian)(dian)源地接(jie)(jie)通(tong)。在该电(dian)(dian)路(lu)中，P沟(gou)(gou)道(dao)(dao)(dao)(dao)MOS场(chang)(chang)效(xiao)应(ying)(ying)(ying)管和N沟(gou)(gou)道(dao)(dao)(dao)(dao)MOS场(chang)(chang)效(xiao)应(ying)(ying)(ying)管总是在相(xiang)反的状(zhuang)态下(xia)(xia)工作(zuo)，其(qi)相(xiang)位输入端(duan)(duan)(duan)和输出端(duan)(duan)(duan)相(xiang)反。通(tong)过这种工作(zuo)方式(shi)我们(men)可以(yi)获得较大的电(dian)(dian)流输出。
图3
同时由于漏(lou)电流的影响，使得(de)栅(zha)压(ya)在(zai)还(hai)没有到0V，通(tong)常在(zai)栅(zha)极电压(ya)小于1到2V时，MOS场(chang)效(xiao)应管(guan)既(ji)被关断(duan)。不(bu)同场(chang)效(xiao)应管(guan)其关断(duan)电压(ya)略有不(bu)同。也(ye)正因(yin)为如此，使得(de)该(gai)电路(lu)不(bu)会因(yin)为两管(guan)同时导通(tong)而造(zao)成电源(yuan)短路(lu)。
图(tu)4
由以(yi)上(shang)分析我们可以(yi)画(hua)出(chu)原理图中MOS场效应管(guan)电路部分的(de)工作过(guo)程（见(jian)图4）。工作原理同前所(suo)述。
场效应晶体管的(de)参数(shu)(shu)(shu)(shu)很(hen)多，包括直流参数(shu)(shu)(shu)(shu)、交流参数(shu)(shu)(shu)(shu)和极限参数(shu)(shu)(shu)(shu)，但一般使用时只(zhi)需要关注(zhu)以下(xia)几项(xiang)主要参数(shu)(shu)(shu)(shu)。
①夹断电(dian)压（UP）。这是指在(zai)规(gui)定的(de)漏极电(dian)压UDS下，使漏极电(dian)流(liu)/D（即沟(gou)道电(dian)流(liu)）为(wei)零或者小于某一小电(dian)流(liu)值(zhi)（例如1μA. 10μA）时(shi)，加在(zai)栅(zha)极上的(de)电(dian)压UGS它是结型或耗(hao)尽型绝(jue)缘栅(zha)场效应晶(jing)体管的(de)重要参数。
②开启(qi)电压(ya)(ya)(UT)。这是指当(dang)(dang)漏极电压(ya)(ya)UDS为某一(yi)规定值时，使导电沟(gou)道（即漏、源极之(zhi)间）刚开始(shi)导通时的(de)栅极电压(ya)(ya)UGS它是增强型场(chang)效应晶体(ti)管(guan)的(de)重(zhong)要参(can)数。当(dang)(dang)栅极电压(ya)(ya)UGS小(xiao)于开启(qi)电压(ya)(ya)坼的(de)绝对值时，场(chang)效应晶体(ti)管(guan)不能导通。：
③饱和(he)漏(lou)(lou)电(dian)(dian)流(/DSS)。这是指当栅(zha)、源(yuan)极短路(lu)(UGS=0)时，一(yi)定的漏(lou)(lou)极电(dian)(dian)压UDS（大于夹(jia)断(duan)电(dian)(dian)压）所引起的漏(lou)(lou)极电(dian)(dian)流/D饱和(he)漏(lou)(lou)电(dian)(dian)流反映了零栅(zha)压时原始沟道的导电(dian)(dian)能力(li)，是耗(hao)尽型场效应晶(jing)体(ti)管的重要参数。
④低频跨导(gm)，在漏极(ji)(ji)(ji)电压UDS为规(gui)定值时，漏极(ji)(ji)(ji)电流(liu)变化量△/D与引(yin)起这个(ge)变化的(de)栅压变化量△UGS的(de)比值，叫(jiao)跨导（或互(hu)导），即gm=△/D/△UGS。gm的(de)常用单位是(shi)mS（毫西门(men)子(zi)(zi)(zi)）gm是(shi)衡量场效应晶(jing)体(ti)管栅极(ji)(ji)(ji)电压对漏极(ji)(ji)(ji)电流(liu)控制能力强(qiang)弱的(de)一个(ge)参数(shu)，也(ye)是(shi)衡量放大作用的(de)重要(yao)参数(shu)，与晶(jing)体(ti)三极(ji)(ji)(ji)管的(de)交流(liu)电流(liu)放大系数(shu)β相似。gm与管子(zi)(zi)(zi)的(de)工作区域有(you)关，漏极(ji)(ji)(ji)电流(liu)/D越大，管子(zi)(zi)(zi)的(de)跨导gm也(ye)越大。
⑤漏源(yuan)击穿(chuan)电(dian)压(ya)（BUDS）。这是指栅极(ji)(ji)(ji)电(dian)压(ya)UGS一定时(shi)，场(chang)效(xiao)应(ying)(ying)晶(jing)体(ti)管正常工作所能承受(shou)的(de)最大漏极(ji)(ji)(ji)电(dian)压(ya)，它相(xiang)当于(yu)普通晶(jing)体(ti)三极(ji)(ji)(ji)管的(de)集电(dian)极(ji)(ji)(ji)一发(fa)射极(ji)(ji)(ji)击穿(chuan)电(dian)压(ya)V(BR)ceo（即BUceo）。这是一项极(ji)(ji)(ji)限参数，使用时(shi)加在(zai)场(chang)效(xiao)应(ying)(ying)晶(jing)体(ti)管上(shang)的(de)工作电(dian)压(ya)必须小于(yu)BUDS。
⑥最大漏源电流(liu)( /DSM)。这是指场效应晶(jing)体管正常工作时(shi)，漏、源极(ji)之间所允许通过的最大电流(liu)，它相当于普(pu)通晶(jing)体三极(ji)管的/CM场效应晶(jing)体管的工作电流(liu)不应超过这一极(ji)限参数(shu)。
⑦最大耗散功(gong)率(PDSM)。这(zhei)是指场效应(ying)(ying)晶体(ti)管性(xing)能不变坏时(shi)，所允许的(de)最大漏极(ji)耗散功(gong)率，它(ta)相当于普通三极(ji)管的(de)Pcm。使用(yong)时(shi)，场效应(ying)(ying)晶体(ti)管的(de)实(shi)际功(gong)耗（PD=UDS×/D）应(ying)(ying)小(xiao)于这(zhei)一(yi)(yi)极(ji)限(xian)参数，并留有一(yi)(yi)定余量。
对(dui)于下(xia)图(a)所示的(de)(de)金(jin)属管(guan)(guan)帽(mao)封装的(de)(de)三引(yin)(yin)脚(jiao)(jiao)(jiao)圆柱(zhu)状(zhuang)场效(xiao)(xiao)应管(guan)(guan)，其管(guan)(guan)帽(mao)下(xia)有一个(ge)小凸口，把引(yin)(yin)脚(jiao)(jiao)(jiao)对(dui)着自(zi)己，从凸口开始沿顺时针方向数，如果(guo)是结型(xing)场效(xiao)(xiao)应管(guan)(guan)，依次(ci)为(wei)源极(ji)S、漏极(ji)D和栅(zha)极(ji)G；如果(guo)是绝(jue)缘栅(zha)型(xing)场效(xiao)(xiao)应管(guan)(guan)，则(ze)依次(ci)为(wei)D、G和S脚(jiao)(jiao)(jiao)。对(dui)于塑料封装的(de)(de)半圆柱(zhu)状(zhuang)结型(xing)场效(xiao)(xiao)应管(guan)(guan)，其3个(ge)引(yin)(yin)线脚(jiao)(jiao)(jiao)呈“一字形(xing)”排列，面对(dui)标有型(xing)号的(de)(de)一面，从左到右依次(ci)为(wei)S、D、G脚(jiao)(jiao)(jiao)。对(dui)于下(xia)图(b)所示的(de)(de)金(jin)属管(guan)(guan)帽(mao)封装的(de)(de)四引(yin)(yin)脚(jiao)(jiao)(jiao)绝(jue)缘栅(zha)型(xing)场效(xiao)(xiao)应管(guan)(guan)，其增(zeng)加的(de)(de)第4引(yin)(yin)脚(jiao)(jiao)(jiao)有两种可能，如果(guo)是普通增(zeng)强型(xing)MOS场效(xiao)(xiao)应管(guan)(guan)，则(ze)该(gai)脚(jiao)(jiao)(jiao)为(wei)“衬底”引(yin)(yin)脚(jiao)(jiao)(jiao)；如果(guo)是双栅(zha)MOS管(guan)(guan)，则(ze)该(gai)脚(jiao)(jiao)(jiao)为(wei)第二栅(zha)极(ji)引(yin)(yin)脚(jiao)(jiao)(jiao)。
对(dui)于(yu)有4个(ge)引脚(jiao)(jiao)(jiao)的结型(xing)场(chang)(chang)效应晶(jing)体(ti)(ti)管(guan)，其(qi)增(zeng)加的第4脚(jiao)(jiao)(jiao)一般是屏蔽极(ji)(ji)（使用中接(jie)(jie)地）。对(dui)于(yu)大功率场(chang)(chang)效应晶(jing)体(ti)(ti)管(guan)，将(jiang)管(guan)子有字(zi)面朝自己、引脚(jiao)(jiao)(jiao)朝下，从左至(zhi)右其(qi)引脚(jiao)(jiao)(jiao)排列顺序(xu)基本(ben)上(shang)都(dou)是“G、D、S”，并且散热片(pian)接(jie)(jie)通D极(ji)(ji)。，当遇(yu)到型(xing)号、封装(zhuang)和(he)引脚(jiao)(jiao)(jiao)排列不(bu)熟悉的场(chang)(chang)效应晶(jing)体(ti)(ti)管(guan)时(shi)，就要查阅有关资料或(huo)用万(wan)用表(biao)检测辨认(ren)后再(zai)接(jie)(jie)入(ru)电(dian)路。
其中(zhong)结(jie)(jie)型(xing)(xing)(xing)(xing)(xing)(xing)场(chang)(chang)(chang)效(xiao)(xiao)应(ying)(ying)(ying)(ying)(ying)管(guan)(guan)(guan)(guan)(guan)(guan)的(de)图(tu)形(xing)(xing)符(fu)号(hao)(hao)中(zhong)，竖直线(xian)(xian)(xian)(xian)表示(shi)(shi)(shi)(shi)能导(dao)电(dian)的(de)沟(gou)(gou)(gou)道(dao)(dao)(dao)(dao)，竖直线(xian)(xian)(xian)(xian)顶部(bu)(bu)的(de)一条直角线(xian)(xian)(xian)(xian)表示(shi)(shi)(shi)(shi)漏极(ji)(ji)(ji)D，竖直线(xian)(xian)(xian)(xian)底部(bu)(bu)的(de)一条直角线(xian)(xian)(xian)(xian)表示(shi)(shi)(shi)(shi)源(yuan)(yuan)极(ji)(ji)(ji)S，竖直线(xian)(xian)(xian)(xian)左面(mian)带箭(jian)(jian)(jian)(jian)头(tou)(tou)(tou)的(de)直线(xian)(xian)(xian)(xian)表示(shi)(shi)(shi)(shi)栅(zha)(zha)极(ji)(ji)(ji)G。同(tong)普通晶(jing)体三(san)极(ji)(ji)(ji)管(guan)(guan)(guan)(guan)(guan)(guan)一样，箭(jian)(jian)(jian)(jian)头(tou)(tou)(tou)指(zhi)向(xiang)(xiang)表示(shi)(shi)(shi)(shi)从(cong)P型(xing)(xing)(xing)(xing)(xing)(xing)指(zhi)向(xiang)(xiang)N型(xing)(xing)(xing)(xing)(xing)(xing)材料(liao)，从(cong)箭(jian)(jian)(jian)(jian)头(tou)(tou)(tou)指(zhi)向(xiang)(xiang)就(jiu)可(ke)(ke)以知道(dao)(dao)(dao)(dao)是(shi)哪种(zhong)沟(gou)(gou)(gou)道(dao)(dao)(dao)(dao)的(de)结(jie)(jie)型(xing)(xing)(xing)(xing)(xing)(xing)场(chang)(chang)(chang)效(xiao)(xiao)应(ying)(ying)(ying)(ying)(ying)管(guan)(guan)(guan)(guan)(guan)(guan)，，很(hen)显(xian)然(ran)，图(tu)形(xing)(xing)符(fu)号(hao)(hao)中(zhong)箭(jian)(jian)(jian)(jian)头(tou)(tou)(tou)指(zhi)向(xiang)(xiang)“沟(gou)(gou)(gou)道(dao)(dao)(dao)(dao)”，表示(shi)(shi)(shi)(shi)是(shi)N型(xing)(xing)(xing)(xing)(xing)(xing)沟(gou)(gou)(gou)道(dao)(dao)(dao)(dao)结(jie)(jie)型(xing)(xing)(xing)(xing)(xing)(xing)场(chang)(chang)(chang)效(xiao)(xiao)应(ying)(ying)(ying)(ying)(ying)管(guan)(guan)(guan)(guan)(guan)(guan)；箭(jian)(jian)(jian)(jian)头(tou)(tou)(tou)背(bei)离(li)“沟(gou)(gou)(gou)道(dao)(dao)(dao)(dao)”，表示(shi)(shi)(shi)(shi)是(shi)P型(xing)(xing)(xing)(xing)(xing)(xing)沟(gou)(gou)(gou)道(dao)(dao)(dao)(dao)结(jie)(jie)型(xing)(xing)(xing)(xing)(xing)(xing)场(chang)(chang)(chang)效(xiao)(xiao)应(ying)(ying)(ying)(ying)(ying)管(guan)(guan)(guan)(guan)(guan)(guan)。由(you)于(yu)结(jie)(jie)型(xing)(xing)(xing)(xing)(xing)(xing)管(guan)(guan)(guan)(guan)(guan)(guan)的(de)源(yuan)(yuan)极(ji)(ji)(ji)S和(he)漏极(ji)(ji)(ji)D在(zai)制造工艺上是(shi)对(dui)称(cheng)的(de)，所以图(tu)形(xing)(xing)符(fu)号(hao)(hao)画法也(ye)很(hen)对(dui)称(cheng)，表示(shi)(shi)(shi)(shi)在(zai)实际应(ying)(ying)(ying)(ying)(ying)用中(zhong)这两个电(dian)极(ji)(ji)(ji)可(ke)(ke)以对(dui)换使用。在(zai)绝缘栅(zha)(zha)型(xing)(xing)(xing)(xing)(xing)(xing)场(chang)(chang)(chang)效(xiao)(xiao)应(ying)(ying)(ying)(ying)(ying)管(guan)(guan)(guan)(guan)(guan)(guan)的(de)图(tu)形(xing)(xing)符(fu)号(hao)(hao)中(zhong)，栅(zha)(zha)极(ji)(ji)(ji)G都不带箭(jian)(jian)(jian)(jian)头(tou)(tou)(tou)，不与“沟(gou)(gou)(gou)道(dao)(dao)(dao)(dao)”竖直线(xian)(xian)(xian)(xian)接触，表示(shi)(shi)(shi)(shi)管(guan)(guan)(guan)(guan)(guan)(guan)中(zhong)栅(zha)(zha)极(ji)(ji)(ji)G与漏极(ji)(ji)(ji)D.源(yuan)(yuan)极(ji)(ji)(ji)S是(shi)绝缘的(de)，以区别(bie)(bie)于(yu)结(jie)(jie)型(xing)(xing)(xing)(xing)(xing)(xing)场(chang)(chang)(chang)效(xiao)(xiao)应(ying)(ying)(ying)(ying)(ying)管(guan)(guan)(guan)(guan)(guan)(guan)。将(jiang)表示(shi)(shi)(shi)(shi)沟(gou)(gou)(gou)道(dao)(dao)(dao)(dao)结(jie)(jie)型(xing)(xing)(xing)(xing)(xing)(xing)的(de)“箭(jian)(jian)(jian)(jian)头(tou)(tou)(tou)”改画在(zai)“沟(gou)(gou)(gou)道(dao)(dao)(dao)(dao)”中(zhong)间表示(shi)(shi)(shi)(shi)“衬(chen)底”的(de)水(shui)平(ping)线(xian)(xian)(xian)(xian)上，即(ji)箭(jian)(jian)(jian)(jian)头(tou)(tou)(tou)指(zhi)向(xiang)(xiang)“沟(gou)(gou)(gou)道(dao)(dao)(dao)(dao)”，表示(shi)(shi)(shi)(shi)是(shi)N型(xing)(xing)(xing)(xing)(xing)(xing)沟(gou)(gou)(gou)道(dao)(dao)(dao)(dao)绝缘栅(zha)(zha)型(xing)(xing)(xing)(xing)(xing)(xing)场(chang)(chang)(chang)效(xiao)(xiao)应(ying)(ying)(ying)(ying)(ying)管(guan)(guan)(guan)(guan)(guan)(guan)；箭(jian)(jian)(jian)(jian)头(tou)(tou)(tou)背(bei)离(li)“沟(gou)(gou)(gou)道(dao)(dao)(dao)(dao)”，表示(shi)(shi)(shi)(shi)是(shi)P型(xing)(xing)(xing)(xing)(xing)(xing)沟(gou)(gou)(gou)道(dao)(dao)(dao)(dao)绝缘栅(zha)(zha)型(xing)(xing)(xing)(xing)(xing)(xing)场(chang)(chang)(chang)效(xiao)(xiao)应(ying)(ying)(ying)(ying)(ying)管(guan)(guan)(guan)(guan)(guan)(guan)。另(ling)外，箭(jian)(jian)(jian)(jian)头(tou)(tou)(tou)线(xian)(xian)(xian)(xian)画的(de)短(duan)，表示(shi)(shi)(shi)(shi)衬(chen)底无(wu)引出(chu)线(xian)(xian)(xian)(xian)；箭(jian)(jian)(jian)(jian)头(tou)(tou)(tou)线(xian)(xian)(xian)(xian)画的(de)稍(shao)长，表示(shi)(shi)(shi)(shi)衬(chen)底有(you)引出(chu)线(xian)(xian)(xian)(xian)；箭(jian)(jian)(jian)(jian)头(tou)(tou)(tou)线(xian)(xian)(xian)(xian)与源(yuan)(yuan)极(ji)(ji)(ji)S相连(lian)，表示(shi)(shi)(shi)(shi)衬(chen)底在(zai)管(guan)(guan)(guan)(guan)(guan)(guan)子内部(bu)(bu)已经与源(yuan)(yuan)极(ji)(ji)(ji)连(lian)接。对(dui)于(yu)增强型(xing)(xing)(xing)(xing)(xing)(xing)的(de)管(guan)(guan)(guan)(guan)(guan)(guan)子，还将(jiang)“沟(gou)(gou)(gou)道(dao)(dao)(dao)(dao)”线(xian)(xian)(xian)(xian)画成(cheng)3截，表示(shi)(shi)(shi)(shi)在(zai)零(ling)栅(zha)(zha)压下这种(zhong)管(guan)(guan)(guan)(guan)(guan)(guan)子是(shi)没有(you)导(dao)电(dian)沟(gou)(gou)(gou)道(dao)(dao)(dao)(dao)的(de)，以区别(bie)(bie)于(yu)耗尽型(xing)(xing)(xing)(xing)(xing)(xing)MOS管(guan)(guan)(guan)(guan)(guan)(guan)和(he)结(jie)(jie)型(xing)(xing)(xing)(xing)(xing)(xing)场(chang)(chang)(chang)效(xiao)(xiao)应(ying)(ying)(ying)(ying)(ying)管(guan)(guan)(guan)(guan)(guan)(guan)。可(ke)(ke)见，掌(zhang)握了场(chang)(chang)(chang)效(xiao)(xiao)应(ying)(ying)(ying)(ying)(ying)晶(jing)体管(guan)(guan)(guan)(guan)(guan)(guan)的(de)这些(xie)图(tu)形(xing)(xing)符(fu)号(hao)(hao)，就(jiu)等于(yu)掌(zhang)握了场(chang)(chang)(chang)效(xiao)(xiao)应(ying)(ying)(ying)(ying)(ying)晶(jing)体管(guan)(guan)(guan)(guan)(guan)(guan)的(de)种(zhong)类，这对(dui)分(fen)析电(dian)路和(he)正(zheng)确运用场(chang)(chang)(chang)效(xiao)(xiao)应(ying)(ying)(ying)(ying)(ying)晶(jing)体管(guan)(guan)(guan)(guan)(guan)(guan)都很(hen)重(zhong)要。
跟普通晶(jing)体三极管(guan)一样(yang)，以前场效应晶(jing)体管(guan)的(de)旧(jiu)图形符号(hao)均用(yong)圆圈(quan)(quan)表(biao)示外壳，现已废弃不(bu)再画出圆圈(quan)(quan)。不(bu)过我们翻阅以前的(de)电路图或图书时(shi)，会看到带有圆圈(quan)(quan)的(de)场效应晶(jing)体管(guan)图形符号(hao)。
场(chang)效应晶体(ti)管的(de)(de)文(wen)(wen)字符(fu)号与普通晶体(ti)三极管的(de)(de)文(wen)(wen)字符(fu)号相同，常(chang)用VT（旧符(fu)号为BG）或V表示(shi)，在电(dian)路图中常(chang)写在图形符(fu)号旁边。若电(dian)路图中有(you)多(duo)只同类元器(qi)件时，按常(chang)规就(jiu)在文(wen)(wen)字后(hou)面或右下(xia)(xia)角标上(shang)数字，以示(shi)区别，如VT1、VT2-文(wen)(wen)字符(fu)号的(de)(de)下(xia)(xia)边，一般标出场(chang)效应晶体(ti)管的(de)(de)型号。
共有两种(zhong)命名(ming)方法。
第一种(zhong)命名(ming)方法与双极型(xing)(xing)(xing)(xing)三(san)极管(guan)相同(tong)，第三(san)位字母J代(dai)表结型(xing)(xing)(xing)(xing)场(chang)效(xiao)应管(guan)，O代(dai)表绝缘栅(zha)场(chang)效(xiao)应管(guan)。第二位字母代(dai)表材(cai)料(liao)，D是P型(xing)(xing)(xing)(xing)硅，反型(xing)(xing)(xing)(xing)层是N沟道(dao)；C是N型(xing)(xing)(xing)(xing)硅P沟道(dao)。例如,3DJ6D是结型(xing)(xing)(xing)(xing)P沟道(dao)场(chang)效(xiao)应三(san)极管(guan)，3DO6C是绝缘栅(zha)型(xing)(xing)(xing)(xing)N沟道(dao)场(chang)效(xiao)应三(san)极管(guan)。
第(di)二种命名方法(fa)是CS××#，CS代(dai)表(biao)场效应管，××以数字(zi)代(dai)表(biao)型(xing)号(hao)的序号(hao)，#用字(zi)母代(dai)表(biao)同一型(xing)号(hao)中(zhong)的不同规格。例如CS14A、CS45G等。
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