利盈娱乐(中国)创新平台有限公司

P沟道MOS管工作原理

金属氧化物半导体场(chang)效(xiao)(xiao)应(ying)(MOS)晶体管可(ke)分为N沟(gou)(gou)(gou)(gou)道(dao)(dao)与(yu)P沟(gou)(gou)(gou)(gou)道(dao)(dao)两(liang)大类， P沟(gou)(gou)(gou)(gou)道(dao)(dao)硅(gui)MOS场(chang)效(xiao)(xiao)应(ying)晶体管在N型(xing)硅(gui)衬(chen)底上有两(liang)个P+区，分别叫做(zuo)源(yuan)极(ji)(ji)和漏(lou)(lou)极(ji)(ji)，两(liang)极(ji)(ji)之(zhi)间不(bu)通导，柵极(ji)(ji)上加(jia)有足够的(de)正电(dian)压(ya)(源(yuan)极(ji)(ji)接(jie)地)时，柵极(ji)(ji)下(xia)的(de)N型(xing)硅(gui)表面(mian)呈(cheng)现P型(xing)反(fan)型(xing)层，成为衔接(jie)源(yuan)极(ji)(ji)和漏(lou)(lou)极(ji)(ji)的(de)沟(gou)(gou)(gou)(gou)道(dao)(dao)。改动(dong)栅(zha)压(ya)可(ke)以改动(dong)沟(gou)(gou)(gou)(gou)道(dao)(dao)中(zhong)的(de)电(dian)子密度，从而(er)改动(dong)沟(gou)(gou)(gou)(gou)道(dao)(dao)的(de)电(dian)阻(zu)。这种(zhong)MOS场(chang)效(xiao)(xiao)应(ying)晶体管称为P沟(gou)(gou)(gou)(gou)道(dao)(dao)增(zeng)强型(xing)场(chang)效(xiao)(xiao)应(ying)晶体管。假设N型(xing)硅(gui)衬(chen)底表面(mian)不(bu)加(jia)栅(zha)压(ya)就已(yi)存在P型(xing)反(fan)型(xing)层沟(gou)(gou)(gou)(gou)道(dao)(dao)，加(jia)上恰当的(de)偏压(ya)，可(ke)使(shi)沟(gou)(gou)(gou)(gou)道(dao)(dao)的(de)电(dian)阻(zu)增(zeng)大或(huo)减小。这样(yang)的(de)MOS场效(xiao)应晶体管称(cheng)(cheng)为P沟道耗尽型场效(xiao)应(ying)晶体(ti)(ti)管(guan)。统(tong)称(cheng)(cheng)为PMOS晶体(ti)(ti)管(guan)。

P沟(gou)(gou)道(dao)MOS晶(jing)体管(guan)(guan)(guan)的(de)(de)空穴迁移(yi)率低，因而(er)在MOS晶(jing)体管(guan)(guan)(guan)的(de)(de)几何尺寸和工(gong)作(zuo)电(dian)(dian)(dian)压绝对值相等的(de)(de)情况下，PMOS晶(jing)体管(guan)(guan)(guan)的(de)(de)跨(kua)导小(xiao)于N沟(gou)(gou)道(dao)MOS晶(jing)体管(guan)(guan)(guan)。此外，P沟(gou)(gou)道(dao)MOS晶(jing)体管(guan)(guan)(guan)阈值电(dian)(dian)(dian)压的(de)(de)绝对值普通偏高，恳(ken)求有(you)较高的(de)(de)工(gong)作(zuo)电(dian)(dian)(dian)压。它的(de)(de)供电(dian)(dian)(dian)电(dian)(dian)(dian)源的(de)(de)电(dian)(dian)(dian)压大小(xiao)和极性(xing)，与双极型晶(jing)体管(guan)(guan)(guan)——晶(jing)体管(guan)(guan)(guan)逻辑(ji)电(dian)(dian)(dian)路(lu)不兼容。PMOS因逻辑(ji)摆幅大，充电(dian)(dian)(dian)放电(dian)(dian)(dian)过程长(zhang)，加之(zhi)器件(jian)跨(kua)导小(xiao)，所以工(gong)作(zuo)速度(du)更(geng)低，在NMOS电(dian)(dian)(dian)路(lu)(见N沟(gou)(gou)道(dao)金属—氧化物—半导体集成电(dian)(dian)(dian)路(lu))呈现之(zhi)后，多数已为(wei)NMOS电(dian)(dian)(dian)路(lu)所取代。只是(shi)，因PMOS电(dian)(dian)(dian)路(lu)工(gong)艺(yi)简单(dan)，价钱低价，有(you)些中范(fan)围(wei)和小(xiao)范(fan)围(wei)数字控制电(dian)(dian)(dian)路(lu)仍采用PMOS电路(lu)技术。PMOS的(de)特性(xing)，Vgs小于(yu)一定的(de)值(zhi)就会导通(tong)，适宜用于(yu)源极接VCC时(shi)的(de)情况（高端(duan)驱(qu)动(dong)）。但(dan)是，固然PMOS可以很便当(dang)地(di)用作高端(duan)驱(qu)动(dong)，但(dan)由于(yu)导通(tong)电阻大，价钱(qian)贵，交流种类少等缘由，在高端(duan)驱(qu)动(dong)中，通(tong)常还是运用NMOS。

正常(chang)工作时(shi)，P沟(gou)(gou)道增强型(xing)MOS管(guan)的(de)衬底必需与源极相连，而漏(lou)心极的(de)电压Vds应为负(fu)值(zhi)，以保证(zheng)两个(ge)P区与衬底之(zhi)间的(de)PN结均为反偏，同时(shi)为了在衬底顶(ding)表(biao)面(mian)左近构成导电沟(gou)(gou)道，栅极对源极的(de)电压Vgs也(ye)应为负(fu)。

1．Ｖds≠Ｏ的(de)(de)情况导(dao)电(dian)(dian)沟(gou)道(dao)构成以后(hou)，ＤＳ间(jian)加(jia)负(fu)向电(dian)(dian)压时，那(nei)么在源(yuan)极(ji)与(yu)漏极(ji)之间(jian)将有漏极(ji)电(dian)(dian)流Ｉd流通，而(er)(er)且Ｉd随Vds而(er)(er)增加(jia)．Ｉd沿(yan)沟(gou)道(dao)产生的(de)(de)压降使沟(gou)道(dao)上各点(dian)与(yu)栅(zha)极(ji)间(jian)的(de)(de)电(dian)(dian)压不再相等，该(gai)电(dian)(dian)压削(xue)弱了(le)栅(zha)极(ji)中(zhong)负(fu)电(dian)(dian)荷电(dian)(dian)场的(de)(de)作用，使沟(gou)道(dao)从漏极(ji)到(dao)源(yuan)极(ji)逐(zhu)渐(jian)变窄．当Ｖds增大到(dao)使Ｖgd＝Ｖgs（TH），沟(gou)道(dao)在漏极(ji)左近呈现(xian)预夹断．

2．导(dao)(dao)电(dian)(dian)(dian)(dian)沟(gou)道的(de)(de)构(gou)成(cheng)（Ｖds＝0）当Vds=0时(shi)(shi)，在(zai)栅源之间加负(fu)电(dian)(dian)(dian)(dian)压(ya)Vgs，由于绝缘层(ceng)(ceng)(ceng)的(de)(de)存(cun)在(zai)，故没有电(dian)(dian)(dian)(dian)流，但(dan)是(shi)金(jin)属栅极被补充电(dian)(dian)(dian)(dian)而(er)聚集(ji)负(fu)电(dian)(dian)(dian)(dian)荷，Ｎ型半导(dao)(dao)体(ti)中(zhong)的(de)(de)多子(zi)(zi)电(dian)(dian)(dian)(dian)子(zi)(zi)被负(fu)电(dian)(dian)(dian)(dian)荷排斥向(xiang)体(ti)内运动，表面(mian)留(liu)下带正电(dian)(dian)(dian)(dian)的(de)(de)离子(zi)(zi)，构(gou)成(cheng)耗尽层(ceng)(ceng)(ceng)，随着Ｇ、Ｓ间负(fu)电(dian)(dian)(dian)(dian)压(ya)的(de)(de)增(zeng)加，耗尽层(ceng)(ceng)(ceng)加宽，当Vgs增(zeng)大(da)到一定(ding)值时(shi)(shi)，衬底中(zhong)的(de)(de)空(kong)穴（少子(zi)(zi)）被栅极中(zhong)的(de)(de)负(fu)电(dian)(dian)(dian)(dian)荷吸(xi)收到表面(mian)，在(zai)耗尽层(ceng)(ceng)(ceng)和绝缘层(ceng)(ceng)(ceng)之间构(gou)成(cheng)一个Ｐ型薄层(ceng)(ceng)(ceng)，称反型层(ceng)(ceng)(ceng)，这个反型层(ceng)(ceng)(ceng)就构(gou)成(cheng)漏源之间的(de)(de)导(dao)(dao)电(dian)(dian)(dian)(dian)沟(gou)道，这时(shi)(shi)的(de)(de)Ｖgs称为(wei)开启电(dian)(dian)(dian)(dian)压(ya)Vgs（th），Vgs到Vgs（th）后再(zai)(zai)增(zeng)加，衬底表面(mian)感应的(de)(de)空(kong)穴越(yue)多，反型层(ceng)(ceng)(ceng)加宽，而(er)耗尽层(ceng)(ceng)(ceng)的(de)(de)宽度(du)却不再(zai)(zai)变化，这样我们可以用(yong)Vgs的(de)(de)大(da)小控(kong)制导(dao)(dao)电(dian)(dian)(dian)(dian)沟(gou)道的(de)(de)宽度(du)。

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