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P沟道MOS管工作原理金属氧化物半导体场效应(MOS)晶体管可分为N沟道与P沟道两大类， P沟道硅MOS场效应晶体管在N型硅衬底上有两个P+区，分别叫做源(yuan)极和漏极，两极之间不通导，柵极上加有足够的正电压(源极接地)时，柵极下的N型硅表面呈现P型反型层，成为衔接源极和漏极的沟道。

PMOS的特性，Vgs小于一定的值就会导通，适合用于源极接VCC时的情况（高端驱动）。但是，固然PMOS可以很便当地用作高端驱动，但由于导通电阻大，价钱贵，交流种类少等缘由，在高端驱动中，通常还是运用NMOS。电路分析如下：pmos的开启条件是VGS电压为负压，并且电压的绝对值大于最低开启电压，普通小功率的PMOS管的最小开启电压为0.7V左右，假定电池充溢电，电压为4.2V,VGS=-4.2V，PMOS是导通的(de)(de)(de)(de)，电(dian)(dian)(dian)(dian)(dian)(dian)(dian)路是没(mei)(mei)有(you)问(wen)题的(de)(de)(de)(de)。当(dang)5V电(dian)(dian)(dian)(dian)(dian)(dian)(dian)压(ya)时，G极(ji)(ji)的(de)(de)(de)(de)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)压(ya)为(wei)(wei)5V，S极(ji)(ji)的(de)(de)(de)(de)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)压(ya)为(wei)(wei)5VV-二极(ji)(ji)管压(ya)降(jiang)(jiang)（0.5左(zuo)右(you)）=4.5V，PMOS管关(guan)段，当(dang)没(mei)(mei)有(you)5V电(dian)(dian)(dian)(dian)(dian)(dian)(dian)压(ya)时，G极(ji)(ji)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)压(ya)下拉为(wei)(wei)0V，S极(ji)(ji)的(de)(de)(de)(de)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)压(ya)为(wei)(wei)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)池电(dian)(dian)(dian)(dian)(dian)(dian)(dian)压(ya)（假定电(dian)(dian)(dian)(dian)(dian)(dian)(dian)池充溢电(dian)(dian)(dian)(dian)(dian)(dian)(dian)4.2V）-MOS管未导通二极(ji)(ji)管压(ya)降(jiang)(jiang)（0.5V）=3.7，这样PMOS就导通，二极(ji)(ji)管压(ya)降(jiang)(jiang)就没(mei)(mei)有(you)了这样VGS=-4.2V.PMOS管导通对负(fu)载供(gong)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)。在(zai)这里(li)用(yong)一个肖(xiao)特(te)基(ji)二极(ji)(ji)管（SS12）也(ye)可(ke)以处置这个问(wen)题，不过就是有(you)0.3V左(zuo)右(you)的(de)(de)(de)(de)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)压(ya)降(jiang)(jiang)。这里(li)运用(yong)PMOS管，PMOS管完好导通，内(nei)阻(zu)(zu)比较小，优与肖(xiao)特(te)基(ji)，几乎没(mei)(mei)有(you)压(ya)降(jiang)(jiang)。不过下拉电(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)运用(yong)的(de)(de)(de)(de)有(you)点大，驱动PMOS不需(xu)求(qiu)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)流的(de)(de)(de)(de)，只需(xu)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)压(ya)抵达就可(ke)以了，可(ke)以运用(yong)大电(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)，减少工作电(dian)(dian)(dian)(dian)(dian)(dian)(dian)流，推(tui)荐(jian)运用(yong)10K-100K左(zuo)右(you)的(de)(de)(de)(de)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)。

P沟道MOS晶体管的空穴迁移率低,因而在MOS晶体管的几何尺寸和工作电压绝对值相等的情况下，PMOS晶体管的跨导小于N沟道MOS晶体管。此外，P沟道MOS晶体管阈值电压的绝对值普通偏高，央求有较高的工作电压。它的供电电源的电压大小和极性,与双极型晶体管——晶体管逻辑电路不兼容。PMOS因逻辑摆幅大，充电放电过程长，加之器件跨导小，所以工作速度更低，在NMOS电路(见N沟道金属—氧化物—半导体集成电路)呈现之后，多数已为NMOS电路所取代。只是,因PMOS电路工艺简单,价钱低价，有些中范围和小范围数字控制电路仍采用PMOS电路技术。
改(gai)(gai)动栅压可以改(gai)(gai)动沟(gou)道(dao)(dao)中的(de)(de)电(dian)子密度，从(cong)而改(gai)(gai)动沟(gou)道(dao)(dao)的(de)(de)电(dian)阻。这种(zhong)MOS场效(xiao)应晶(jing)体(ti)(ti)(ti)管(guan)称为P沟(gou)道(dao)(dao)增强型(xing)(xing)场效(xiao)应晶(jing)体(ti)(ti)(ti)管(guan)。假(jia)定N型(xing)(xing)硅衬底表(biao)面(mian)不加(jia)栅压就已存在P型(xing)(xing)反型(xing)(xing)层沟(gou)道(dao)(dao)，加(jia)上恰当(dang)的(de)(de)偏压，可使(shi)沟(gou)道(dao)(dao)的(de)(de)电(dian)阻增大或减小(xiao)。这样的(de)(de)MOS场效(xiao)应晶(jing)体(ti)(ti)(ti)管(guan)称为P沟(gou)道(dao)(dao)耗尽(jin)型(xing)(xing)场效(xiao)应晶(jing)体(ti)(ti)(ti)管(guan)。统称为PMOS晶(jing)体(ti)(ti)(ti)管(guan)。

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