利盈娱乐(中国)创新平台有限公司

什么(me)是MOS管MOS管的(de)英文全称叫MOSFET(Metal Oxide Semiconductor Field Effect Transistor)，即金属氧化(hua)物半导体型(xing)场效(xiao)应管，属于(yu)场效(xiao)应管中的(de)绝缘(yuan)栅型(xing)。因此，MOS管有时被称为绝缘(yuan)栅场效(xiao)应管。在普通电子(zi)电路中，MOS管通常被用(yong)于(yu)放大电路或开关电路。

1、MOS管的构造

在(zai)一(yi)(yi)块掺(chan)杂浓(nong)度较低的(de)(de)P型半导体硅衬底上，用半导体光刻、扩(kuo)散工艺制造(zao)两个(ge)高掺(chan)杂浓(nong)度的(de)(de)N+区(qu)，并用金属(shu)铝引出两个(ge)电(dian)极，分(fen)别(bie)作为漏极D和(he)源极S。然(ran)后(hou)在(zai)漏极和(he)源极之间(jian)的(de)(de)P型半导体表(biao)(biao)面复盖(gai)一(yi)(yi)层(ceng)很薄(bo)的(de)(de)二氧化(hua)硅（Si02）绝(jue)缘层(ceng)膜，在(zai)再这(zhei)个(ge)绝(jue)缘层(ceng)膜上装上一(yi)(yi)个(ge)铝电(dian)极，作为栅(zha)极G。这(zhei)就构成了一(yi)(yi)个(ge)N沟道（NPN型）增强型MOS管。显然(ran)它(ta)的(de)(de)栅(zha)极和(he)其它(ta)电(dian)极间(jian)是绝(jue)缘的(de)(de)。图(tu)1-1所(suo)示 A 、B分(fen)别(bie)是它(ta)的(de)(de)结构图(tu)和(he)代表(biao)(biao)符号。

同(tong)(tong)样用上(shang)述相同(tong)(tong)的(de)方法在(zai)一块掺(chan)杂浓度(du)较(jiao)低的(de)N型半导(dao)体硅衬底(di)上(shang)，用半导(dao)体光(guang)刻、扩散(san)工艺(yi)制(zhi)造两个高掺(chan)杂浓度(du)的(de)P+区，及上(shang)述相同(tong)(tong)的(de)栅极制(zhi)造过程，就制(zhi)成为一个P沟道(dao)(dao)(dao)（PNP型）增强(qiang)型MOS管(guan)。图(tu)1-2所示A 、B分别(bie)是P沟道(dao)(dao)(dao)MOS管(guan)道(dao)(dao)(dao)结构图(tu)和代表符号。

2、MOS管的工作原理

从图1-3-A可以看出(chu)，增强型MOS管(guan)(guan)的(de)(de)漏(lou)(lou)极(ji)(ji)(ji)D和源(yuan)(yuan)极(ji)(ji)(ji)S之间有(you)两(liang)个(ge)(ge)背靠背的(de)(de)PN结。当(dang)栅(zha)(zha)(zha)-源(yuan)(yuan)电(dian)(dian)(dian)(dian)(dian)(dian)压(ya)(ya)VGS=0时，即(ji)使加(jia)(jia)上漏(lou)(lou)-源(yuan)(yuan)电(dian)(dian)(dian)(dian)(dian)(dian)压(ya)(ya)VDS，总有(you)一(yi)个(ge)(ge)PN结处于反偏状态，漏(lou)(lou)-源(yuan)(yuan)极(ji)(ji)(ji)间没(mei)有(you)导电(dian)(dian)(dian)(dian)(dian)(dian)沟(gou)道(dao)（没(mei)有(you)电(dian)(dian)(dian)(dian)(dian)(dian)流(liu)流(liu)过），所以这时漏(lou)(lou)极(ji)(ji)(ji)电(dian)(dian)(dian)(dian)(dian)(dian)流(liu)ID=0。此时若在(zai)栅(zha)(zha)(zha)-源(yuan)(yuan)极(ji)(ji)(ji)间加(jia)(jia)上正向(xiang)电(dian)(dian)(dian)(dian)(dian)(dian)压(ya)(ya)，图1-3-B所示，即(ji)VGS＞0，则栅(zha)(zha)(zha)极(ji)(ji)(ji)和硅衬(chen)(chen)底(di)之间的(de)(de)SiO2绝(jue)缘层中(zhong)便(bian)产生一(yi)个(ge)(ge)栅(zha)(zha)(zha)极(ji)(ji)(ji)指向(xiang)P型硅衬(chen)(chen)底(di)的(de)(de)电(dian)(dian)(dian)(dian)(dian)(dian)场，由(you)于氧(yang)化物(wu)层是(shi)绝(jue)缘的(de)(de)，栅(zha)(zha)(zha)极(ji)(ji)(ji)所加(jia)(jia)电(dian)(dian)(dian)(dian)(dian)(dian)压(ya)(ya)VGS无(wu)法构成(cheng)电(dian)(dian)(dian)(dian)(dian)(dian)流(liu)，氧(yang)化物(wu)层的(de)(de)两(liang)边就构成(cheng)了一(yi)个(ge)(ge)电(dian)(dian)(dian)(dian)(dian)(dian)容，VGS等效是(shi)对这个(ge)(ge)电(dian)(dian)(dian)(dian)(dian)(dian)容充电(dian)(dian)(dian)(dian)(dian)(dian)，并构成(cheng)一(yi)个(ge)(ge)电(dian)(dian)(dian)(dian)(dian)(dian)场，随(sui)着VGS逐(zhu)渐升高，受栅(zha)(zha)(zha)极(ji)(ji)(ji)正电(dian)(dian)(dian)(dian)(dian)(dian)压(ya)(ya)的(de)(de)吸收(shou)，在(zai)这个(ge)(ge)电(dian)(dian)(dian)(dian)(dian)(dian)容的(de)(de)另一(yi)边就聚(ju)集(ji)大(da)量的(de)(de)电(dian)(dian)(dian)(dian)(dian)(dian)子并构成(cheng)了一(yi)个(ge)(ge)从漏(lou)(lou)极(ji)(ji)(ji)到(dao)源(yuan)(yuan)极(ji)(ji)(ji)的(de)(de)N型导电(dian)(dian)(dian)(dian)(dian)(dian)沟(gou)道(dao)，当(dang)VGS大(da)于管(guan)(guan)子的(de)(de)开启电(dian)(dian)(dian)(dian)(dian)(dian)压(ya)(ya)VT（普(pu)通(tong)约为 2V）时，N沟(gou)道(dao)管(guan)(guan)开端(duan)导通(tong)，构成(cheng)漏(lou)(lou)极(ji)(ji)(ji)电(dian)(dian)(dian)(dian)(dian)(dian)流(liu)ID，我们把开端(duan)构成(cheng)沟(gou)道(dao)时的(de)(de)栅(zha)(zha)(zha)-源(yuan)(yuan)极(ji)(ji)(ji)电(dian)(dian)(dian)(dian)(dian)(dian)压(ya)(ya)称为开启电(dian)(dian)(dian)(dian)(dian)(dian)压(ya)(ya)，普(pu)通(tong)用VT表示。控制(zhi)(zhi)栅(zha)(zha)(zha)极(ji)(ji)(ji)电(dian)(dian)(dian)(dian)(dian)(dian)压(ya)(ya)VGS的(de)(de)大(da)小改动(dong)了电(dian)(dian)(dian)(dian)(dian)(dian)场的(de)(de)强弱，就可以抵达(da)控制(zhi)(zhi)漏(lou)(lou)极(ji)(ji)(ji)电(dian)(dian)(dian)(dian)(dian)(dian)流(liu)ID的(de)(de)大(da)小的(de)(de)目的(de)(de)，这也(ye)是(shi)MOS管(guan)(guan)用电(dian)(dian)(dian)(dian)(dian)(dian)场来控制(zhi)(zhi)电(dian)(dian)(dian)(dian)(dian)(dian)流(liu)的(de)(de)一(yi)个(ge)(ge)重要特性，所以也(ye)称之为场效应管(guan)(guan)。

3、MOS管的(de)特性(xing)

上述MOS管(guan)的(de)(de)(de)工作原理中可以看出，MOS管(guan)的(de)(de)(de)栅(zha)(zha)(zha)极(ji)(ji)G和(he)源(yuan)极(ji)(ji)S之(zhi)(zhi)间是绝缘的(de)(de)(de)，由于Sio2绝缘层(ceng)的(de)(de)(de)存(cun)在，在栅(zha)(zha)(zha)极(ji)(ji)G和(he)源(yuan)极(ji)(ji)S之(zhi)(zhi)间等效是一个电(dian)(dian)(dian)容(rong)存(cun)在，电(dian)(dian)(dian)压VGS产生(sheng)电(dian)(dian)(dian)场从(cong)而招致源(yuan)极(ji)(ji)-漏(lou)极(ji)(ji)电(dian)(dian)(dian)流(liu)(liu)(liu)的(de)(de)(de)产生(sheng)。此(ci)时的(de)(de)(de)栅(zha)(zha)(zha)极(ji)(ji)电(dian)(dian)(dian)压VGS决(jue)议了漏(lou)极(ji)(ji)电(dian)(dian)(dian)流(liu)(liu)(liu)的(de)(de)(de)大(da)(da)小，控(kong)制栅(zha)(zha)(zha)极(ji)(ji)电(dian)(dian)(dian)压VGS的(de)(de)(de)大(da)(da)小就可以控(kong)制漏(lou)极(ji)(ji)电(dian)(dian)(dian)流(liu)(liu)(liu)ID的(de)(de)(de)大(da)(da)小。这(zhei)就可以得(de)出如下结(jie)论：1） MOS管(guan)是一个由改(gai)动电(dian)(dian)(dian)压来控(kong)制电(dian)(dian)(dian)流(liu)(liu)(liu)的(de)(de)(de)器(qi)件(jian)，所以是电(dian)(dian)(dian)压器(qi)件(jian)。2） MOS管(guan)道输入(ru)特(te)性为容(rong)性特(te)性，所以输入(ru)阻抗(kang)极(ji)(ji)高。

4、MOS管的电压和符号

图(tu)1-4-A 是(shi)N沟(gou)道MOS管的(de)符(fu)号，图(tu)中D是(shi)漏极(ji)，S是(shi)源(yuan)极(ji)，G是(shi)栅(zha)极(ji)，中间的(de)箭(jian)头表(biao)示(shi)衬(chen)底，如果箭(jian)头向(xiang)(xiang)里(li)表(biao)示(shi)是(shi)N沟(gou)道的(de)MOS管，箭(jian)头向(xiang)(xiang)外表(biao)示(shi)是(shi)P沟(gou)道的(de)MOS管。

在实际(ji)MOS管生(sheng)产的(de)(de)过程中衬底(di)在出厂前就和(he)源极(ji)连接(jie)，所(suo)以在符(fu)号的(de)(de)规则中；表示衬底(di)的(de)(de)箭(jian)头也必须(xu)和(he)源极(ji)相连接(jie)，以区别漏极(ji)和(he)源极(ji)。图1-5-A是P沟道MOS管的(de)(de)符(fu)号。

MOS管应用电(dian)(dian)压的极性和我们普通的晶体(ti)三极管相同，N沟(gou)(gou)道的类(lei)似(si)NPN晶体(ti)三极管，漏极D接正(zheng)极，源极S接负极，栅极G正(zheng)电(dian)(dian)压时导电(dian)(dian)沟(gou)(gou)道建(jian)立，N沟(gou)(gou)道MOS管开(kai)(kai)始工作(zuo),如图1-4-B所示。同样P道的类(lei)似(si)PNP晶体(ti)三极管，漏极D接负极，源极S接正(zheng)极，栅极G负电(dian)(dian)压时，导电(dian)(dian)沟(gou)(gou)道建(jian)立，P沟(gou)(gou)道MOS管开(kai)(kai)始工作(zuo),如图1-5-B所示。

5、MOS在开关电源电路

1）、大(da)(da)功(gong)(gong)率(lv)MOS管和大(da)(da)功(gong)(gong)率(lv)晶体三极(ji)(ji)(ji)管相比MOS管的优点；1)、输(shu)(shu)入(ru)阻(zu)(zu)抗高，驱动(dong)(dong)(dong)功(gong)(gong)率(lv)小(xiao)：由于栅源(yuan)之(zhi)间(jian)是(shi)二(er)氧化硅（SiO2）绝缘(yuan)层(ceng)，栅源(yuan)之(zhi)间(jian)的直(zhi)流电阻(zu)(zu)基(ji)本(ben)上就(jiu)(jiu)是(shi)SiO2绝缘(yuan)电阻(zu)(zu)，普(pu)通达(da)100MΩ左右(you)，交流输(shu)(shu)入(ru)阻(zu)(zu)抗基(ji)本(ben)上就(jiu)(jiu)是(shi)输(shu)(shu)入(ru)电容的容抗。由于输(shu)(shu)入(ru)阻(zu)(zu)抗高，对鼓(gu)舞信(xin)号不会产(chan)生压(ya)降，有电压(ya)就(jiu)(jiu)可以驱动(dong)(dong)(dong)，所以驱动(dong)(dong)(dong)功(gong)(gong)率(lv)极(ji)(ji)(ji)小(xiao)（灵敏(min)度(du)高）。普(pu)通的晶体三极(ji)(ji)(ji)管必需有基(ji)极(ji)(ji)(ji)电压(ya)Vb，再产(chan)生基(ji)极(ji)(ji)(ji)电流Ib，才干驱动(dong)(dong)(dong)集(ji)电极(ji)(ji)(ji)电流的产(chan)生。晶体三极(ji)(ji)(ji)管的驱动(dong)(dong)(dong)是(shi)需求(qiu)功(gong)(gong)率(lv)的（Vb×Ib）。

2）、开(kai)关(guan)(guan)(guan)(guan)速(su)(su)度快(kuai)(kuai):MOSFET的(de)(de)(de)开(kai)关(guan)(guan)(guan)(guan)速(su)(su)度和输(shu)入的(de)(de)(de)容(rong)性(xing)(xing)特(te)性(xing)(xing)的(de)(de)(de)有很大(da)关(guan)(guan)(guan)(guan)系，由于输(shu)入容(rong)性(xing)(xing)特(te)性(xing)(xing)的(de)(de)(de)存在(zai)，使开(kai)关(guan)(guan)(guan)(guan)的(de)(de)(de)速(su)(su)度变(bian)慢，但是在(zai)作(zuo)为开(kai)关(guan)(guan)(guan)(guan)运用(yong)时，可降低驱(qu)动(dong)电(dian)路(lu)内阻，加快(kuai)(kuai)开(kai)关(guan)(guan)(guan)(guan)速(su)(su)度（输(shu)入采(cai)用(yong)了后(hou)述的(de)(de)(de)“灌流电(dian)路(lu)”驱(qu)动(dong)，加快(kuai)(kuai)了容(rong)性(xing)(xing)的(de)(de)(de)充放(fang)电(dian)的(de)(de)(de)时间）。MOSFET只靠多子(zi)导(dao)电(dian)，不存在(zai)少(shao)子(zi)储存效应，因而(er)关(guan)(guan)(guan)(guan)断过程非(fei)常疾速(su)(su)，开(kai)关(guan)(guan)(guan)(guan)时间在(zai)10—100ns之间，工作(zuo)频率可达100kHz以(yi)上，普通(tong)的(de)(de)(de)晶体三极管(guan)(guan)由于少(shao)数(shu)载流子(zi)的(de)(de)(de)存储效应，使开(kai)关(guan)(guan)(guan)(guan)总有滞后(hou)现象，影(ying)响(xiang)开(kai)关(guan)(guan)(guan)(guan)速(su)(su)度的(de)(de)(de)进步（目前采(cai)用(yong)MOS管(guan)(guan)的(de)(de)(de)开(kai)关(guan)(guan)(guan)(guan)电(dian)源其工作(zuo)频率可以(yi)随意的(de)(de)(de)做到(dao)100K/S～150K/S,这关(guan)(guan)(guan)(guan)于普通(tong)的(de)(de)(de)大(da)功率晶体三极管(guan)(guan)来说是难(nan)以(yi)想象的(de)(de)(de)）。

3）、无二(er)次击(ji)(ji)穿(chuan)；由于普通(tong)的(de)(de)功率晶(jing)体三(san)极(ji)(ji)管(guan)(guan)具有当温(wen)(wen)度(du)(du)上(shang)(shang)升就(jiu)会招致(zhi)(zhi)集电(dian)(dian)(dian)极(ji)(ji)电(dian)(dian)(dian)流上(shang)(shang)升（正的(de)(de)温(wen)(wen)度(du)(du)～电(dian)(dian)(dian)流特(te)性(xing)(xing)(xing)）的(de)(de)现象(xiang)，而(er)集电(dian)(dian)(dian)极(ji)(ji)电(dian)(dian)(dian)流的(de)(de)上(shang)(shang)升又会招致(zhi)(zhi)温(wen)(wen)度(du)(du)进一(yi)(yi)(yi)(yi)步(bu)的(de)(de)上(shang)(shang)升，温(wen)(wen)度(du)(du)进一(yi)(yi)(yi)(yi)步(bu)的(de)(de)上(shang)(shang)升，更进一(yi)(yi)(yi)(yi)步(bu)的(de)(de)招致(zhi)(zhi)集电(dian)(dian)(dian)极(ji)(ji)电(dian)(dian)(dian)流的(de)(de)上(shang)(shang)升这(zhei)一(yi)(yi)(yi)(yi)恶性(xing)(xing)(xing)循(xun)环。而(er)晶(jing)体三(san)极(ji)(ji)管(guan)(guan)的(de)(de)耐压VCEO随管(guan)(guan)温(wen)(wen)度(du)(du)升高是逐步(bu)降(jiang)(jiang)(jiang)落，这(zhei)就(jiu)构成(cheng)了管(guan)(guan)温(wen)(wen)继续(xu)上(shang)(shang)升、耐压继续(xu)降(jiang)(jiang)(jiang)落最终招致(zhi)(zhi)晶(jing)体三(san)极(ji)(ji)管(guan)(guan)的(de)(de)击(ji)(ji)穿(chuan)，这(zhei)是一(yi)(yi)(yi)(yi)种招致(zhi)(zhi)电(dian)(dian)(dian)视(shi)机开(kai)关(guan)电(dian)(dian)(dian)源管(guan)(guan)和行输(shu)出(chu)管(guan)(guan)损(sun)坏率占95%的(de)(de)破环性(xing)(xing)(xing)的(de)(de)热(re)电(dian)(dian)(dian)击(ji)(ji)穿(chuan)现象(xiang)，也称为(wei)二(er)次击(ji)(ji)穿(chuan)现象(xiang)。MOS管(guan)(guan)具有和普通(tong)晶(jing)体三(san)极(ji)(ji)管(guan)(guan)相(xiang)反的(de)(de)温(wen)(wen)度(du)(du)～电(dian)(dian)(dian)流特(te)性(xing)(xing)(xing)，即当管(guan)(guan)温(wen)(wen)度(du)(du)（或环境温(wen)(wen)度(du)(du)）上(shang)(shang)升时，沟(gou)道(dao)电(dian)(dian)(dian)流IDS反而(er)降(jiang)(jiang)(jiang)落。例如；一(yi)(yi)(yi)(yi)只IDS=10A的(de)(de)MOS FET开(kai)关(guan)管(guan)(guan)，当VGS控制电(dian)(dian)(dian)压不变时，在250C温(wen)(wen)度(du)(du)下IDS=3A，当芯片温(wen)(wen)度(du)(du)升高为(wei)1000C时，IDS降(jiang)(jiang)(jiang)低(di)到2A，这(zhei)种因温(wen)(wen)度(du)(du)上(shang)(shang)升而(er)招致(zhi)(zhi)沟(gou)道(dao)电(dian)(dian)(dian)流IDS降(jiang)(jiang)(jiang)落的(de)(de)负(fu)温(wen)(wen)度(du)(du)电(dian)(dian)(dian)流特(te)性(xing)(xing)(xing)，使之不会产生恶性(xing)(xing)(xing)循(xun)环而(er)热(re)击(ji)(ji)穿(chuan)。也就(jiu)是MOS管(guan)(guan)没有二(er)次击(ji)(ji)穿(chuan)现象(xiang)，可见采用(yong)MOS管(guan)(guan)作为(wei)开(kai)关(guan)管(guan)(guan)，其(qi)开(kai)关(guan)管(guan)(guan)的(de)(de)损(sun)坏率大(da)幅(fu)度(du)(du)的(de)(de)降(jiang)(jiang)(jiang)低(di)，近两年电(dian)(dian)(dian)视(shi)机开(kai)关(guan)电(dian)(dian)(dian)源采用(yong)MOS管(guan)(guan)替代过去的(de)(de)普通(tong)晶(jing)体三(san)极(ji)(ji)管(guan)(guan)后，开(kai)关(guan)管(guan)(guan)损(sun)坏率大(da)大(da)降(jiang)(jiang)(jiang)低(di)也是一(yi)(yi)(yi)(yi)个极(ji)(ji)好的(de)(de)证明。

4）、MOS管(guan)(guan)(guan)导(dao)(dao)(dao)(dao)(dao)通后(hou)其导(dao)(dao)(dao)(dao)(dao)通特性(xing)(xing)呈(cheng)纯阻(zu)(zu)(zu)性(xing)(xing)；普通晶体(ti)(ti)三极(ji)(ji)(ji)管(guan)(guan)(guan)在饱(bao)(bao)和(he)导(dao)(dao)(dao)(dao)(dao)通是(shi)(shi)(shi)，几乎是(shi)(shi)(shi)直(zhi)通，有一个(ge)(ge)极(ji)(ji)(ji)低(di)的(de)(de)(de)压(ya)(ya)降，称为(wei)饱(bao)(bao)和(he)压(ya)(ya)降，既(ji)然(ran)有一个(ge)(ge)压(ya)(ya)降，那么也就(jiu)(jiu)是(shi)(shi)(shi)；普通晶体(ti)(ti)三极(ji)(ji)(ji)管(guan)(guan)(guan)在饱(bao)(bao)和(he)导(dao)(dao)(dao)(dao)(dao)通后(hou)等(deng)效(xiao)(xiao)是(shi)(shi)(shi)一个(ge)(ge)阻(zu)(zu)(zu)值极(ji)(ji)(ji)小(xiao)的(de)(de)(de)电(dian)阻(zu)(zu)(zu)，但是(shi)(shi)(shi)这个(ge)(ge)等(deng)效(xiao)(xiao)的(de)(de)(de)电(dian)阻(zu)(zu)(zu)是(shi)(shi)(shi)一个(ge)(ge)非(fei)线(xian)(xian)(xian)性(xing)(xing)的(de)(de)(de)电(dian)阻(zu)(zu)(zu)（电(dian)阻(zu)(zu)(zu)上的(de)(de)(de)电(dian)压(ya)(ya)和(he)流(liu)过(guo)(guo)的(de)(de)(de)电(dian)流(liu)不(bu)能契合(he)欧姆定律），而MOS管(guan)(guan)(guan)作为(wei)开关管(guan)(guan)(guan)应用(yong)，在饱(bao)(bao)和(he)导(dao)(dao)(dao)(dao)(dao)通后(hou)也存在一个(ge)(ge)阻(zu)(zu)(zu)值极(ji)(ji)(ji)小(xiao)的(de)(de)(de)电(dian)阻(zu)(zu)(zu)，但是(shi)(shi)(shi)这个(ge)(ge)电(dian)阻(zu)(zu)(zu)等(deng)效(xiao)(xiao)一个(ge)(ge)线(xian)(xian)(xian)性(xing)(xing)电(dian)阻(zu)(zu)(zu)，其电(dian)阻(zu)(zu)(zu)的(de)(de)(de)阻(zu)(zu)(zu)值和(he)两端的(de)(de)(de)电(dian)压(ya)(ya)降和(he)流(liu)过(guo)(guo)的(de)(de)(de)电(dian)流(liu)契合(he)欧姆定律的(de)(de)(de)关系(xi)，电(dian)流(liu)大压(ya)(ya)降就(jiu)(jiu)大，电(dian)流(liu)小(xiao)压(ya)(ya)降就(jiu)(jiu)小(xiao)，导(dao)(dao)(dao)(dao)(dao)通后(hou)既(ji)然(ran)等(deng)效(xiao)(xiao)是(shi)(shi)(shi)一个(ge)(ge)线(xian)(xian)(xian)性(xing)(xing)元件(jian)，线(xian)(xian)(xian)性(xing)(xing)元件(jian)就(jiu)(jiu)可以并联应用(yong)，当(dang)这样两个(ge)(ge)电(dian)阻(zu)(zu)(zu)并联在一同(tong)，就(jiu)(jiu)有一个(ge)(ge)自动电(dian)流(liu)平衡(heng)的(de)(de)(de)作用(yong)，所以MOS管(guan)(guan)(guan)在一个(ge)(ge)管(guan)(guan)(guan)子功率不(bu)够的(de)(de)(de)时分，可以多(duo)管(guan)(guan)(guan)并联应用(yong)，且不(bu)用(yong)另外(wai)增(zeng)加(jia)平衡(heng)措施（非(fei)线(xian)(xian)(xian)性(xing)(xing)器件(jian)是(shi)(shi)(shi)不(bu)能直(zhi)接并联应用(yong)的(de)(de)(de)）。

二：灌流(liu)电路

1、MOS管作(zuo)为开关管的驱动电路；

在(zai)图(tu)(tu)2-2中；在(zai)作(zuo)为(wei)开(kai)(kai)关(guan)应用的(de)(de)(de)(de)MOS管(guan)Q3的(de)(de)(de)(de)栅极(ji)(ji)(ji)S和(he)鼓舞信(xin)号(hao)之间(jian)(jian)(jian)增(zeng)加Q1、Q2两(liang)(liang)只开(kai)(kai)关(guan)管(guan)，此两(liang)(liang)虽然均为(wei)普通(tong)(tong)的(de)(de)(de)(de)晶体三极(ji)(ji)(ji)管(guan)，两(liang)(liang)虽然接成串联(lian)衔接，Q1为(wei)NPN型Q2为(wei)PNP型，基极(ji)(ji)(ji)衔接在(zai)一同(tong)（理论上是(shi)(shi)一个PNP、NPN互补(bu)的(de)(de)(de)(de)射极(ji)(ji)(ji)跟随器），两(liang)(liang)虽然等(deng)效是(shi)(shi)两(liang)(liang)只在(zai)方波(bo)鼓舞信(xin)号(hao)控制(zhi)下轮番导(dao)通(tong)(tong)的(de)(de)(de)(de)开(kai)(kai)关(guan)，如图(tu)(tu)2-2-A、图(tu)(tu)2-2-B当鼓舞方波(bo)信(xin)号(hao)的(de)(de)(de)(de)正(zheng)半(ban)周来到时；晶体三极(ji)(ji)(ji)管(guan)Q1（NPN）导(dao)通(tong)(tong)、Q2（PNP）截止(zhi)，VCC经过Q1导(dao)通(tong)(tong)对MOS开(kai)(kai)关(guan)管(guan)Q3的(de)(de)(de)(de)栅极(ji)(ji)(ji)充电，由(you)于Q1是(shi)(shi)饱和(he)导(dao)通(tong)(tong)，VCC等(deng)效是(shi)(shi)直接加到MOS管(guan)Q3的(de)(de)(de)(de)栅极(ji)(ji)(ji)，瞬间(jian)(jian)(jian)充电电流极(ji)(ji)(ji)大，充电时间(jian)(jian)(jian)极(ji)(ji)(ji)短(duan)，保证(zheng)了(le)MOS开(kai)(kai)关(guan)管(guan)Q3的(de)(de)(de)(de)疾速的(de)(de)(de)(de)“开(kai)(kai)”，如图(tu)(tu)2-2-A所(suo)(suo)示（图(tu)(tu)2-2-A和(he)图(tu)(tu)2-2-B中的(de)(de)(de)(de)电容C为(wei)MOS管(guan)栅极(ji)(ji)(ji)S的(de)(de)(de)(de)等(deng)效电容）。当鼓舞方波(bo)信(xin)号(hao)的(de)(de)(de)(de)负半(ban)周来到时；晶体三极(ji)(ji)(ji)管(guan)Q1（NPN）截止(zhi)、Q2（PNP）导(dao)通(tong)(tong)，MOS开(kai)(kai)关(guan)管(guan)Q3的(de)(de)(de)(de)栅极(ji)(ji)(ji)所(suo)(suo)充的(de)(de)(de)(de)电荷，经过Q2疾速放电，由(you)于Q2是(shi)(shi)饱和(he)导(dao)通(tong)(tong)，放电时间(jian)(jian)(jian)极(ji)(ji)(ji)短(duan)，保证(zheng)了(le)MOS开(kai)(kai)关(guan)管(guan)Q3的(de)(de)(de)(de)疾速的(de)(de)(de)(de)“关(guan)”，如图(tu)(tu)2-2-B所(suo)(suo)示。

由于MOS管(guan)在制(zhi)造工(gong)艺(yi)上栅(zha)(zha)极S的(de)(de)(de)(de)引线(xian)的(de)(de)(de)(de)电(dian)(dian)(dian)流(liu)(liu)(liu)容量有(you)一定的(de)(de)(de)(de)限(xian)度，所以(yi)在Q1在饱和导通时VCC对MOS管(guan)栅(zha)(zha)极S的(de)(de)(de)(de)瞬时充电(dian)(dian)(dian)电(dian)(dian)(dian)流(liu)(liu)(liu)庞大，极易损坏MOS管(guan)的(de)(de)(de)(de)输(shu)入端，为了维护MOS管(guan)的(de)(de)(de)(de)安(an)全，在细致的(de)(de)(de)(de)电(dian)(dian)(dian)路(lu)中必需(xu)采(cai)取措施限(xian)制(zhi)瞬时充电(dian)(dian)(dian)的(de)(de)(de)(de)电(dian)(dian)(dian)流(liu)(liu)(liu)值，在栅(zha)(zha)极充电(dian)(dian)(dian)的(de)(de)(de)(de)电(dian)(dian)(dian)路(lu)中串接一个恰当的(de)(de)(de)(de)充电(dian)(dian)(dian)限(xian)流(liu)(liu)(liu)电(dian)(dian)(dian)阻R，如图2-3-A所示(shi)。充电(dian)(dian)(dian)限(xian)流(liu)(liu)(liu)电(dian)(dian)(dian)阻R的(de)(de)(de)(de)阻值的(de)(de)(de)(de)选取；要根据MOS管(guan)的(de)(de)(de)(de)输(shu)入电(dian)(dian)(dian)容的(de)(de)(de)(de)大小(xiao)(xiao)，鼓舞脉冲的(de)(de)(de)(de)频(pin)率及灌(guan)流(liu)(liu)(liu)电(dian)(dian)(dian)路(lu)的(de)(de)(de)(de)VCC（VCC普(pu)通为12V）的(de)(de)(de)(de)大小(xiao)(xiao)决(jue)议(yi)普(pu)通在数十姆欧到(dao)一百欧姆之(zhi)间。

由(you)于充电(dian)(dian)(dian)(dian)(dian)限(xian)流电(dian)(dian)(dian)(dian)(dian)阻的(de)(de)(de)增加，使(shi)在(zai)(zai)(zai)鼓舞(wu)方波负半周时(shi)(shi)Q2导通时(shi)(shi)放(fang)电(dian)(dian)(dian)(dian)(dian)的(de)(de)(de)速度(du)遭(zao)到限(xian)制（充电(dian)(dian)(dian)(dian)(dian)时(shi)(shi)是VCC产(chan)生(sheng)电(dian)(dian)(dian)(dian)(dian)流，放(fang)电(dian)(dian)(dian)(dian)(dian)时(shi)(shi)是栅(zha)极(ji)所充的(de)(de)(de)电(dian)(dian)(dian)(dian)(dian)压(ya)VGS产(chan)生(sheng)电(dian)(dian)(dian)(dian)(dian)流，VGS远远小于VCC,R的(de)(de)(de)存在(zai)(zai)(zai)大(da)大(da)的(de)(de)(de)降低了(le)放(fang)电(dian)(dian)(dian)(dian)(dian)的(de)(de)(de)速率）使(shi)MOS管(guan)(guan)的(de)(de)(de)开关特(te)性变坏，为了(le)使(shi)R阻值在(zai)(zai)(zai)放(fang)电(dian)(dian)(dian)(dian)(dian)时(shi)(shi)不影响疾速放(fang)电(dian)(dian)(dian)(dian)(dian)的(de)(de)(de)速率，在(zai)(zai)(zai)充电(dian)(dian)(dian)(dian)(dian)限(xian)流电(dian)(dian)(dian)(dian)(dian)阻R上(shang)并(bing)联一个(ge)构成(cheng)放(fang)电(dian)(dian)(dian)(dian)(dian)通路的(de)(de)(de)二极(ji)管(guan)(guan)D，图2-3-B所示。此二极(ji)管(guan)(guan)在(zai)(zai)(zai)放(fang)电(dian)(dian)(dian)(dian)(dian)时(shi)(shi)导通，在(zai)(zai)(zai)充电(dian)(dian)(dian)(dian)(dian)时(shi)(shi)反(fan)偏截止。这样增加了(le)充电(dian)(dian)(dian)(dian)(dian)限(xian)流电(dian)(dian)(dian)(dian)(dian)阻和放(fang)电(dian)(dian)(dian)(dian)(dian)二极(ji)管(guan)(guan)后，既(ji)保(bao)证(zheng)了(le)MOS管(guan)(guan)的(de)(de)(de)安(an)全，又(you)保(bao)证(zheng)了(le)MOS管(guan)(guan)，“开”与“关”的(de)(de)(de)疾速动作。

2、另一种灌流电路灌流电路的另外一种方式，关(guan)于某些功(gong)率较小(xiao)的开关(guan)电源上采用的MOS管常(chang)常(chang)采用了(le)图2-4-A的电路方式。

D为充(chong)电(dian)(dian)(dian)二极(ji)管(guan)(guan)，Q为放(fang)电(dian)(dian)(dian)三(san)极(ji)管(guan)(guan)（PNP）。工作过程是这样(yang)，当(dang)鼓舞方波正半(ban)周时(shi)，D导(dao)(dao)通(tong)，对MOS管(guan)(guan)输入端等效(xiao)电(dian)(dian)(dian)容充(chong)电(dian)(dian)(dian)(此时(shi)Q截止)，在当(dang)鼓舞方波负半(ban)周时(shi)，D截止，Q导(dao)(dao)通(tong)，MOS管(guan)(guan)栅极(ji)S所充(chong)电(dian)(dian)(dian)荷，经过Q放(fang)电(dian)(dian)(dian)，MOS管(guan)(guan)完成“开(kai)”与“关”的动作，如图2-4-B所示。此电(dian)(dian)(dian)路(lu)由鼓舞信号直(zhi)接“灌流”，鼓舞信号源恳求内阻较低。该电(dian)(dian)(dian)路(lu)普通(tong)应用(yong)在功(gong)率(lv)较小的开(kai)关电(dian)(dian)(dian)源上。

2、MOS管开关(guan)应用中的作用

MOS管(guan)(guan)在(zai)(zai)开(kai)关状(zhuang)态(tai)(tai)工作(zuo)时(shi)；Q1、Q2是(shi)轮番导(dao)通，MOS管(guan)(guan)栅(zha)(zha)极(ji)(ji)(ji)是(shi)在(zai)(zai)反复充电(dian)(dian)(dian)、放(fang)(fang)电(dian)(dian)(dian)的(de)(de)(de)状(zhuang)态(tai)(tai)，假设在(zai)(zai)此(ci)时(shi)关闭电(dian)(dian)(dian)源(yuan)，MOS管(guan)(guan)的(de)(de)(de)栅(zha)(zha)极(ji)(ji)(ji)就(jiu)有(you)两种状(zhuang)态(tai)(tai)；一个状(zhuang)态(tai)(tai)是(shi)；放(fang)(fang)电(dian)(dian)(dian)状(zhuang)态(tai)(tai)，栅(zha)(zha)极(ji)(ji)(ji)等(deng)效(xiao)电(dian)(dian)(dian)容(rong)没有(you)电(dian)(dian)(dian)荷(he)存(cun)储，一个状(zhuang)态(tai)(tai)是(shi)；充电(dian)(dian)(dian)状(zhuang)态(tai)(tai)，栅(zha)(zha)极(ji)(ji)(ji)等(deng)效(xiao)电(dian)(dian)(dian)容(rong)正(zheng)好处于电(dian)(dian)(dian)荷(he)充溢状(zhuang)态(tai)(tai)，图(tu)2-5-A所示。固(gu)然电(dian)(dian)(dian)源(yuan)切断，此(ci)时(shi)Q1、Q2也都处于断开(kai)状(zhuang)态(tai)(tai)，电(dian)(dian)(dian)荷(he)没有(you)释放(fang)(fang)的(de)(de)(de)回路，MOS管(guan)(guan)栅(zha)(zha)极(ji)(ji)(ji)的(de)(de)(de)电(dian)(dian)(dian)场仍然存(cun)在(zai)(zai)（能坚持很长时(shi)间(jian)(jian)），树立导(dao)电(dian)(dian)(dian)沟道(dao)的(de)(de)(de)条件并没有(you)消(xiao)逝。这样在(zai)(zai)再次开(kai)机瞬间(jian)(jian)，由(you)于鼓舞信(xin)号(hao)还没有(you)树立，而开(kai)机瞬间(jian)(jian)MOS管(guan)(guan)的(de)(de)(de)漏极(ji)(ji)(ji)电(dian)(dian)(dian)源(yuan)(VDS)随(sui)机提供,在(zai)(zai)导(dao)电(dian)(dian)(dian)沟道(dao)的(de)(de)(de)作(zuo)用下(xia)，MOS管(guan)(guan)即刻(ke)产生(sheng)不受控(kong)的(de)(de)(de)庞大漏极(ji)(ji)(ji)电(dian)(dian)(dian)流ID，惹起MOS管(guan)(guan)烧坏。为了避免此(ci)现(xian)象产生(sheng)，在(zai)(zai)MOS管(guan)(guan)的(de)(de)(de)栅(zha)(zha)极(ji)(ji)(ji)对源(yuan)极(ji)(ji)(ji)并接(jie)一只泄放(fang)(fang)电(dian)(dian)(dian)阻(zu)R1，如(ru)图(tu)2-5-B所示，关机后栅(zha)(zha)极(ji)(ji)(ji)存(cun)储的(de)(de)(de)电(dian)(dian)(dian)荷(he)经过R1疾(ji)速(su)释放(fang)(fang)，此(ci)电(dian)(dian)(dian)阻(zu)的(de)(de)(de)阻(zu)值不可太(tai)大，以保证电(dian)(dian)(dian)荷(he)的(de)(de)(de)疾(ji)速(su)释放(fang)(fang)，普通在(zai)(zai)5K～数(shu)10K左(zuo)右。

灌流(liu)(liu)电路主要是(shi)针对MOS管在(zai)作(zuo)为开关(guan)管运(yun)用(yong)时其容性(xing)的输入特性(xing)，惹起“开”、“关(guan)”动(dong)作(zuo)滞后而设置的电路，当MOS管作(zuo)为其他用(yong)途；例如线(xian)性(xing)放大等应用(yong)，就没有(you)必要设置灌流(liu)(liu)电路。

联系方式(shi)：邹先生

联系(xi)电话：0755-83888366-8022

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