利盈娱乐(中国)创新平台有限公司

MOS场效应(ying)晶体管(guan)通常简称为场效应管，是一种应用场效应原理工作的半导体器件，外形如图4-2，所示。和普通双极型晶体管相比拟，场效应管具有输入阻抗高、噪声低、动态范围大、功耗小、易于集成等特性，得到了越来越普遍的应用.

绝缘栅场效(xiao)应(ying)(ying)管也叫(jiao)做金属氧化(hua)物半导体场效(xiao)应(ying)(ying)管，简称为(wei)MOS场效(xiao)应(ying)(ying)管，分为(wei)耗尽(jin)型MOS管和增强(qiang)型MOS管。

1，MOS管种类和结构
MOSFET管(guan)(guan)是(shi)FET的(de)(de)(de)一(yi)种(zhong)（另一(yi)种(zhong)是(shi)JFET），可以(yi)(yi)被(bei)制(zhi)构成增(zeng)强型(xing)(xing)或(huo)(huo)耗尽型(xing)(xing)，P沟(gou)道(dao)(dao)或(huo)(huo)N沟(gou)道(dao)(dao)共4种(zhong)类型(xing)(xing)，但理论(lun)应用(yong)的(de)(de)(de)只需增(zeng)强型(xing)(xing)的(de)(de)(de)N沟(gou)道(dao)(dao)MOS管(guan)(guan)和(he)增(zeng)强型(xing)(xing)的(de)(de)(de)P沟(gou)道(dao)(dao)MOS管(guan)(guan)，所以(yi)(yi)通常提到(dao)NMOS，或(huo)(huo)者PMOS指的(de)(de)(de)就(jiu)是(shi)这(zhei)两种(zhong)。至于为什么不运用(yong)耗尽型(xing)(xing)的(de)(de)(de)MOS管(guan)(guan)，不建议寻(xun)根究(jiu)底(di)。关于这(zhei)两种(zhong)增(zeng)强型(xing)(xing)MOS管(guan)(guan)，比较常用(yong)的(de)(de)(de)是(shi)NMOS。缘由是(shi)导通电(dian)阻小，且容易(yi)制(zhi)造。所以(yi)(yi)开(kai)关电(dian)源(yuan)和(he)马达(da)驱(qu)动(dong)(dong)的(de)(de)(de)应用(yong)中(zhong)，普通都用(yong)NMOS。下面的(de)(de)(de)引见中(zhong)，也多以(yi)(yi)NMOS为主。 MOS管(guan)(guan)的(de)(de)(de)三个(ge)(ge)管(guan)(guan)脚之间有寄(ji)生电(dian)容存在(zai)(zai)(zai)，这(zhei)不是(shi)我们需求的(de)(de)(de)，而是(shi)由于制(zhi)造工(gong)艺限制(zhi)产生的(de)(de)(de)。寄(ji)生电(dian)容的(de)(de)(de)存在(zai)(zai)(zai)使得在(zai)(zai)(zai)设计或(huo)(huo)选择驱(qu)动(dong)(dong)电(dian)路的(de)(de)(de)时分要省事(shi)一(yi)些，但没有办(ban)法避免，后边(bian)再细(xi)致引见。在(zai)(zai)(zai)MOS管(guan)(guan)原理图上可以(yi)(yi)看到(dao)，漏极(ji)(ji)和(he)源(yuan)极(ji)(ji)之间有一(yi)个(ge)(ge)寄(ji)生二(er)极(ji)(ji)管(guan)(guan)。这(zhei)个(ge)(ge)叫体二(er)极(ji)(ji)管(guan)(guan)，在(zai)(zai)(zai)驱(qu)动(dong)(dong)理性负载，这(zhei)个(ge)(ge)二(er)极(ji)(ji)管(guan)(guan)很重要。顺便说一(yi)句，体二(er)极(ji)(ji)管(guan)(guan)只在(zai)(zai)(zai)单个(ge)(ge)的(de)(de)(de)MOS管(guan)(guan)中(zhong)存在(zai)(zai)(zai)，在(zai)(zai)(zai)集(ji)成电(dian)路芯(xin)片(pian)内部通常是(shi)没有的(de)(de)(de)。

2，MOS管导通(tong)特性

导(dao)通(tong)(tong)的(de)(de)(de)意义是作(zuo)为开(kai)关，相当于开(kai)关闭合。NMOS的(de)(de)(de)特性(xing)，Vgs大(da)于一定的(de)(de)(de)值(zhi)就(jiu)(jiu)会导(dao)通(tong)(tong)，适(shi)宜(yi)用(yong)(yong)于源极接地时(shi)的(de)(de)(de)情况（低端(duan)驱(qu)动），只需栅(zha)极电压抵达(da)4V或10V就(jiu)(jiu)可以了。PMOS的(de)(de)(de)特性(xing)，Vgs小于一定的(de)(de)(de)值(zhi)就(jiu)(jiu)会导(dao)通(tong)(tong)，适(shi)宜(yi)用(yong)(yong)于源极接VCC时(shi)的(de)(de)(de)情况（高端(duan)驱(qu)动）。但(dan)是，固然PMOS可以很便当地用(yong)(yong)作(zuo)高端(duan)驱(qu)动，但(dan)由于导(dao)通(tong)(tong)电阻大(da)，价钱贵，交(jiao)流种类少(shao)等缘由，在高端(duan)驱(qu)动中，通(tong)(tong)常还是运(yun)用(yong)(yong)NMOS。

3，MOS开关管
损(sun)(sun)(sun)失(shi)不管(guan)(guan)是(shi)NMOS还是(shi)PMOS，导(dao)(dao)(dao)通(tong)后都有(you)导(dao)(dao)(dao)通(tong)电(dian)(dian)(dian)阻存在，这样电(dian)(dian)(dian)流就会在这个(ge)(ge)电(dian)(dian)(dian)阻上(shang)消(xiao)耗能量，这部分(fen)消(xiao)耗的(de)(de)能量叫做导(dao)(dao)(dao)通(tong)损(sun)(sun)(sun)耗。选择(ze)导(dao)(dao)(dao)通(tong)电(dian)(dian)(dian)阻小(xiao)(xiao)的(de)(de)MOS管(guan)(guan)会减小(xiao)(xiao)导(dao)(dao)(dao)通(tong)损(sun)(sun)(sun)耗。往常(chang)的(de)(de)小(xiao)(xiao)功率MOS管(guan)(guan)导(dao)(dao)(dao)通(tong)电(dian)(dian)(dian)阻普通(tong)在几十(shi)毫欧左(zuo)右，几毫欧的(de)(de)也有(you)。MOS在导(dao)(dao)(dao)通(tong)和(he)(he)截止的(de)(de)时分(fen)，一定不是(shi)在瞬间完(wan)成的(de)(de)。MOS两端的(de)(de)电(dian)(dian)(dian)压有(you)一个(ge)(ge)降(jiang)落(luo)的(de)(de)过(guo)(guo)程(cheng)，流过(guo)(guo)的(de)(de)电(dian)(dian)(dian)流有(you)一个(ge)(ge)上(shang)升的(de)(de)过(guo)(guo)程(cheng)，在这段时间内(nei)，MOS管(guan)(guan)的(de)(de)损(sun)(sun)(sun)失(shi)是(shi)电(dian)(dian)(dian)压和(he)(he)电(dian)(dian)(dian)流的(de)(de)乘积，叫做开关(guan)损(sun)(sun)(sun)失(shi)。通(tong)常(chang)开关(guan)损(sun)(sun)(sun)失(shi)比导(dao)(dao)(dao)通(tong)损(sun)(sun)(sun)失(shi)大得多，而(er)且(qie)开关(guan)频(pin)(pin)率越(yue)快，损(sun)(sun)(sun)失(shi)也越(yue)大。导(dao)(dao)(dao)通(tong)瞬间电(dian)(dian)(dian)压和(he)(he)电(dian)(dian)(dian)流的(de)(de)乘积很大，构成的(de)(de)损(sun)(sun)(sun)失(shi)也就很大。缩短开关(guan)时间，可以减小(xiao)(xiao)每次导(dao)(dao)(dao)通(tong)时的(de)(de)损(sun)(sun)(sun)失(shi)；降(jiang)低开关(guan)频(pin)(pin)率，可以减小(xiao)(xiao)单位时间内(nei)的(de)(de)开关(guan)次数。这两种(zhong)办(ban)法都可以减小(xiao)(xiao)开关(guan)损(sun)(sun)(sun)失(shi)。mos管(guan)(guan)

4，MOS管驱动
跟双(shuang)极性晶(jing)体(ti)管(guan)(guan)相比，普(pu)通(tong)(tong)(tong)以(yi)为使MOS管(guan)(guan)导通(tong)(tong)(tong)不需(xu)(xu)求(qiu)电(dian)(dian)(dian)(dian)(dian)(dian)流，只(zhi)需(xu)(xu)GS电(dian)(dian)(dian)(dian)(dian)(dian)压(ya)(ya)高(gao)于(yu)一定(ding)的(de)(de)值，就可以(yi)了(le)(le)。这个(ge)很(hen)容(rong)易做到(dao)，但(dan)(dan)是(shi)，我们还需(xu)(xu)求(qiu)速(su)度。在(zai)MOS管(guan)(guan)的(de)(de)结构中可以(yi)看(kan)(kan)到(dao)，在(zai)GS，GD之间存在(zai)寄生电(dian)(dian)(dian)(dian)(dian)(dian)容(rong)，而(er)MOS管(guan)(guan)的(de)(de)驱(qu)(qu)动(dong)，理论(lun)上(shang)(shang)就是(shi)对(dui)电(dian)(dian)(dian)(dian)(dian)(dian)容(rong)的(de)(de)充放电(dian)(dian)(dian)(dian)(dian)(dian)。对(dui)电(dian)(dian)(dian)(dian)(dian)(dian)容(rong)的(de)(de)充电(dian)(dian)(dian)(dian)(dian)(dian)需(xu)(xu)求(qiu)一个(ge)电(dian)(dian)(dian)(dian)(dian)(dian)流，由于(yu)对(dui)电(dian)(dian)(dian)(dian)(dian)(dian)容(rong)充电(dian)(dian)(dian)(dian)(dian)(dian)瞬(shun)(shun)间可以(yi)把电(dian)(dian)(dian)(dian)(dian)(dian)容(rong)看(kan)(kan)成(cheng)短路，所以(yi)瞬(shun)(shun)间电(dian)(dian)(dian)(dian)(dian)(dian)流会比较(jiao)大(da)。选(xuan)择(ze)/设计(ji)MOS管(guan)(guan)驱(qu)(qu)动(dong)时(shi)第一要留(liu)意的(de)(de)是(shi)可提供(gong)瞬(shun)(shun)间短路电(dian)(dian)(dian)(dian)(dian)(dian)流的(de)(de)大(da)小。第二留(liu)意的(de)(de)是(shi)，普(pu)遍(bian)用于(yu)高(gao)端驱(qu)(qu)动(dong)的(de)(de)NMOS，导通(tong)(tong)(tong)时(shi)需(xu)(xu)求(qiu)是(shi)栅极电(dian)(dian)(dian)(dian)(dian)(dian)压(ya)(ya)大(da)于(yu)源(yuan)极电(dian)(dian)(dian)(dian)(dian)(dian)压(ya)(ya)。而(er)高(gao)端驱(qu)(qu)动(dong)的(de)(de)MOS管(guan)(guan)导通(tong)(tong)(tong)时(shi)源(yuan)极电(dian)(dian)(dian)(dian)(dian)(dian)压(ya)(ya)与漏(lou)极电(dian)(dian)(dian)(dian)(dian)(dian)压(ya)(ya)（VCC）相同(tong)(tong)，所以(yi)这时(shi)栅极电(dian)(dian)(dian)(dian)(dian)(dian)压(ya)(ya)要比VCC大(da)4V或10V。假设在(zai)同(tong)(tong)一个(ge)系统(tong)里，要得到(dao)比VCC大(da)的(de)(de)电(dian)(dian)(dian)(dian)(dian)(dian)压(ya)(ya)，就要特(te)地(di)的(de)(de)升(sheng)压(ya)(ya)电(dian)(dian)(dian)(dian)(dian)(dian)路了(le)(le)。很(hen)多马达驱(qu)(qu)动(dong)器都集成(cheng)了(le)(le)电(dian)(dian)(dian)(dian)(dian)(dian)荷泵，要留(liu)意的(de)(de)是(shi)应该选(xuan)择(ze)适合的(de)(de)外接(jie)电(dian)(dian)(dian)(dian)(dian)(dian)容(rong)，以(yi)得到(dao)足够的(de)(de)短路电(dian)(dian)(dian)(dian)(dian)(dian)流去驱(qu)(qu)动(dong)MOS管(guan)(guan)。上(shang)(shang)边说的(de)(de)4V或10V是(shi)常用的(de)(de)MOS管(guan)(guan)的(de)(de)导通(tong)(tong)(tong)电(dian)(dian)(dian)(dian)(dian)(dian)压(ya)(ya)，设计(ji)时(shi)当(dang)然需(xu)(xu)求(qiu)有一定(ding)的(de)(de)余量。而(er)且电(dian)(dian)(dian)(dian)(dian)(dian)压(ya)(ya)越(yue)(yue)高(gao)，导通(tong)(tong)(tong)速(su)度越(yue)(yue)快，导通(tong)(tong)(tong)电(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)也越(yue)(yue)小。往常也有导通(tong)(tong)(tong)电(dian)(dian)(dian)(dian)(dian)(dian)压(ya)(ya)更小的(de)(de)MOS管(guan)(guan)用在(zai)不同(tong)(tong)的(de)(de)范畴里，但(dan)(dan)在(zai)12V汽车电(dian)(dian)(dian)(dian)(dian)(dian)子(zi)系统(tong)里，普(pu)通(tong)(tong)(tong)4V导通(tong)(tong)(tong)就够用了(le)(le)。

MOS管(guan)主要参数如下：

1. 栅(zha)(zha)源击穿电压BVGS-在增(zeng)加栅(zha)(zha)源电压过程(cheng)中，使栅(zha)(zha)极(ji)电流IG由零开(kai)端剧增(zeng)时的VGS，称为栅(zha)(zha)源击穿电压BVGS。

2.开(kai)启电(dian)压(ya)VT-开(kai)启电(dian)压(ya)（又称阈值(zhi)电(dian)压(ya)）：使(shi)得源极(ji)S和(he)漏极(ji)D之间开(kai)端构成导电(dian)沟道所需的栅极(ji)电(dian)压(ya)；-规(gui)范的N沟道MOS管(guan)，VT约为3～6V；-经过工艺(yi)上的改良(liang)，能够使(shi)MOS管(guan)的VT值(zhi)降到2～3V。

3. 漏源击穿电压BVDS-在VGS=0（加强型）的条件下 ，在增加漏源电压过程中使ID开端剧增时的VDS称为漏源击穿电压BVDS-ID剧增的缘由有下列两个方面：
（1）漏极左近耗尽层的雪崩击穿
（2）漏源极间的(de)穿通击穿-有些MOS管中(zhong)，其沟道长度较(jiao)短(duan)，不(bu)时增加VDS会使(shi)漏区(qu)(qu)(qu)的(de)耗尽层不(bu)时扩展到源区(qu)(qu)(qu)，使(shi)沟道长度为(wei)零，即产(chan)生(sheng)漏源间的(de)穿通，穿通后，源区(qu)(qu)(qu)中(zhong)的(de)多数(shu)载流子，将直(zhi)承受耗尽层电场的(de)吸收，抵达漏区(qu)(qu)(qu)，产(chan)生(sheng)大的(de)ID。

4. 直流(liu)(liu)(liu)输入电(dian)阻RGS-即(ji)在(zai)栅(zha)源极(ji)(ji)之间(jian)加的电(dian)压与栅(zha)极(ji)(ji)电(dian)流(liu)(liu)(liu)之比-这一(yi)特(te)性(xing)有时以流(liu)(liu)(liu)过栅(zha)极(ji)(ji)的栅(zha)流(liu)(liu)(liu)表示-MOS管的RGS能够很容易地(di)超越1010Ω。

5. 低频跨导(dao)gm-在(zai)VDS为(wei)某一(yi)固定数值(zhi)的(de)(de)条(tiao)件下 ，漏极(ji)电(dian)(dian)(dian)流(liu)的(de)(de)微变量和惹起(qi)这个变化的(de)(de)栅源电(dian)(dian)(dian)压(ya)微变量之比称(cheng)为(wei)跨导(dao)-gm反映了栅源电(dian)(dian)(dian)压(ya)对漏极(ji)电(dian)(dian)(dian)流(liu)的(de)(de)控制才(cai)干-是表征MOS管放大(da)才(cai)干的(de)(de)一(yi)个重要参数-普通(tong)在(zai)非常(chang)之几(ji)至几(ji)mA/V的(de)(de)范围内。

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mos场效应管 增强型mos管 n沟道mos管

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