MOS管导(dao)通(tong)电压

MOS管导通特性

金(jin)(jin)属-氧化层(ceng)半导(dao)体(ti)场(chang)(chang)效(xiao)(xiao)晶(jing)(jing)体(ti)管(guan)，简(jian)称金(jin)(jin)氧半场(chang)(chang)效(xiao)(xiao)晶(jing)(jing)体(ti)管(guan)（Metal-Oxide-Semiconductor Field-Effect Transistor MOSFET）是一(yi)种可以广泛(fan)使用在模拟(ni)电(dian)路与数(shu)字电(dian)路的场(chang)(chang)效(xiao)(xiao)晶(jing)(jing)体(ti)管(guan)（field-effect transistor）。MOSFET依照其“通道(dao)”的极性不同，可分为(wei)“N型(xing)”与“P型(xing)”的MOSFET，通常又称为(wei)NMOSFET与PMOSFET，其他简(jian)称尚(shang)包括(kuo)NMOS?FET、PMOSFET、nMOSFET、pMOSFET等。

导(dao)(dao)通(tong)(tong)的(de)(de)意(yi)思是(shi)(shi)作为开(kai)关，相(xiang)当于(yu)(yu)(yu)开(kai)关闭合。NMOS的(de)(de)特性，Vgs大于(yu)(yu)(yu)一定(ding)的(de)(de)值就(jiu)会导(dao)(dao)通(tong)(tong)，适合用于(yu)(yu)(yu)源(yuan)极接地(di)(di)时的(de)(de)情况(低端(duan)(duan)驱(qu)动)，只要栅极电(dian)压达(da)到4V或10V就(jiu)可以(yi)了。PMOS的(de)(de)特性，Vgs小于(yu)(yu)(yu)一定(ding)的(de)(de)值就(jiu)会导(dao)(dao)通(tong)(tong)，使用与源(yuan)极接VCC时的(de)(de)情况(高端(duan)(duan)驱(qu)动)。但是(shi)(shi)，虽然PMOS可以(yi)很方便地(di)(di)用作高端(duan)(duan)驱(qu)动，但由于(yu)(yu)(yu)导(dao)(dao)通(tong)(tong)电(dian)阻大，价格贵，替(ti)换种类(lei)少(shao)等原因，在(zai)高端(duan)(duan)驱(qu)动中，通(tong)(tong)常还是(shi)(shi)使用NMOS。

MOS管导通电压

MOS管导通条件

场(chang)效(xiao)应(ying)(ying)管的(de)导(dao)通与截止由(you)栅(zha)源电(dian)压(ya)来(lai)(lai)控制(zhi)，对于增强型(xing)场(chang)效(xiao)应(ying)(ying)管来(lai)(lai)说(shuo)，N沟(gou)(gou)道的(de)管子加(jia)正(zheng)向电(dian)压(ya)即导(dao)通，P沟(gou)(gou)道的(de)管子则(ze)加(jia)反向电(dian)压(ya)。一般2V～4V就(jiu)可以了(le)。但是(shi)，场(chang)效(xiao)应(ying)(ying)管分为增强型(xing)（常开型(xing)）和(he)耗尽型(xing)（常闭型(xing)），增强型(xing)的(de)管子是(shi)需要加(jia)电(dian)压(ya)才(cai)能导(dao)通的(de)，而耗尽型(xing)管子本(ben)来(lai)(lai)就(jiu)处于导(dao)通状态，加(jia)栅(zha)源电(dian)压(ya)是(shi)为了(le)使其(qi)截止。开关(guan)只有两种状态(tai)(tai)通(tong)和(he)(he)断(duan)，三(san)极(ji)管和(he)(he)场效(xiao)应管工(gong)作(zuo)有三(san)种状态(tai)(tai)，1、截止，2、线性放大，3、饱和(he)(he)（基极(ji)电(dian)(dian)流继(ji)续(xu)增加而集电(dian)(dian)极(ji)电(dian)(dian)流不(bu)再(zai)增加）。使晶(jing)体(ti)管只工(gong)作(zuo)在1和(he)(he)3状态(tai)(tai)的电(dian)(dian)路(lu)称之(zhi)为开关(guan)电(dian)(dian)路(lu)，一般以晶(jing)体(ti)管截止，集电(dian)(dian)极(ji)不(bu)吸收电(dian)(dian)流表(biao)示(shi)关(guan)；以晶(jing)体(ti)管饱和(he)(he)，发(fa)射极(ji)和(he)(he)集电(dian)(dian)极(ji)之(zhi)间的电(dian)(dian)压差(cha)接(jie)(jie)近于(yu)0V时(shi)表(biao)示(shi)开。开关(guan)电(dian)(dian)路(lu)用于(yu)数字电(dian)(dian)路(lu)时(shi)，输出电(dian)(dian)位接(jie)(jie)近0V时(shi)表(biao)示(shi)0，输出电(dian)(dian)位接(jie)(jie)近电(dian)(dian)源(yuan)电(dian)(dian)压时(shi)表(biao)示(shi)1。所以数字集成电(dian)(dian)路(lu)内部的晶(jing)体(ti)管都工(gong)作(zuo)在开关(guan)状态(tai)(tai)。场效应管按(an)沟道分可分为Ｎ沟道和Ｐ沟道管（在符(fu)号图中可看到中间(jian)的箭头(tou)方向不一样(yang)）。

按材料分(fen)可分(fen)为结(jie)型(xing)(xing)(xing)管(guan)(guan)和绝缘栅(zha)型(xing)(xing)(xing)管(guan)(guan)，绝缘栅(zha)型(xing)(xing)(xing)又(you)分(fen)为耗尽型(xing)(xing)(xing)和增强(qiang)型(xing)(xing)(xing)，一般主(zhu)板上大(da)多(duo)(duo)(duo)(duo)是(shi)绝缘栅(zha)型(xing)(xing)(xing)管(guan)(guan)简(jian)称(cheng)(cheng)MOS管(guan)(guan)，并且大(da)多(duo)(duo)(duo)(duo)采(cai)用(yong)增强(qiang)型(xing)(xing)(xing)的Ｎ沟(gou)道，其次(ci)是(shi)增强(qiang)型(xing)(xing)(xing)的Ｐ沟(gou)道，结(jie)型(xing)(xing)(xing)管(guan)(guan)和耗尽型(xing)(xing)(xing)管(guan)(guan)几乎不用(yong)。场(chang)效(xiao)(xiao)应(ying)晶(jing)体管(guan)(guan)（Field Effect Transistor缩写(FET)）简(jian)称(cheng)(cheng)场(chang)效(xiao)(xiao)应(ying)管(guan)(guan).由多(duo)(duo)(duo)(duo)数(shu)载(zai)流(liu)(liu)子参与导(dao)电,也称(cheng)(cheng)为单极(ji)型(xing)(xing)(xing)晶(jing)体管(guan)(guan).它属于电压控制型(xing)(xing)(xing)半(ban)导(dao)体器(qi)件.场(chang)效(xiao)(xiao)应(ying)管(guan)(guan)是(shi)利用(yong)多(duo)(duo)(duo)(duo)数(shu)载(zai)流(liu)(liu)子导(dao)电,所以(yi)称(cheng)(cheng)之为单极(ji)型(xing)(xing)(xing)器(qi)件,而晶(jing)体管(guan)(guan)是(shi)即有多(duo)(duo)(duo)(duo)数(shu)载(zai)流(liu)(liu)子,也利用(yong)少数(shu)载(zai)流(liu)(liu)子导(dao)电,被称(cheng)(cheng)之为双极(ji)型(xing)(xing)(xing)器(qi)件.有些(xie)场(chang)效(xiao)(xiao)应(ying)管(guan)(guan)的源极(ji)和漏极(ji)可以(yi)互换使用(yong),栅(zha)压也可正(zheng)可负,灵活性比晶(jing)体管(guan)(guan)好(hao)。

MOS管导通电压

MOS管导通过程

导通时序可分(fen)为to~t1、t1~t2、 t2~t3 、t3~t4四个时间段(duan)，这四个时间段(duan)有不同的等效(xiao)电路。

1. t0-t1：C GS1 开(kai)始充(chong)电(dian)，栅极电(dian)压还(hai)没(mei)有到(dao)达V GS（th），导电(dian)沟道没(mei)有形成，MOSFET仍(reng)处于关闭(bi)状(zhuang)态。

2. [t1-t2]区间(jian), GS间(jian)电(dian)压到达Vgs（th），DS间(jian)导电(dian)沟道开(kai)始(shi)形成，MOSFET开(kai)启，DS电(dian)流增加到ID, Cgs2 迅速充(chong)电(dian)，Vgs由(you)Vgs（th）指数增长(zhang)到Va。

3. [t2-t3]区间,MOSFET的DS电压降(jiang)至与Vgs相同(tong),产生Millier效应，Cgd电容(rong)(rong)大(da)大(da)增加,栅极(ji)电流持续流过，由于C gd 电容(rong)(rong)急剧(ju)增大(da)，抑制了栅极(ji)电压对Cgs 的充电,从而(er)使得(de)Vgs 近(jin)乎(hu)水平状态，Cgd 电容(rong)(rong)上电压增加,而(er)DS电容(rong)(rong)上的电压继续减(jian)小。

4. [t3-t4]区(qu)间,至(zhi)(zhi)t3时(shi)刻(ke),MOSFET的(de)(de)DS电(dian)(dian)(dian)压(ya)降至(zhi)(zhi)饱和导(dao)通时(shi)的(de)(de)电(dian)(dian)(dian)压(ya),Millier效应影(ying)响变小(xiao)，Cgd 电(dian)(dian)(dian)容变小(xiao)并和Cgs 电(dian)(dian)(dian)容一起由外部驱动(dong)电(dian)(dian)(dian)压(ya)充电(dian)(dian)(dian), Cgs 电(dian)(dian)(dian)容的(de)(de)电(dian)(dian)(dian)压(ya)上升,至(zhi)(zhi)t4时(shi)刻(ke)为止.此时(shi)C gs 电(dian)(dian)(dian)容电(dian)(dian)(dian)压(ya)已达稳态,DS间电(dian)(dian)(dian)压(ya)也达最小(xiao)，MOSFET完全开(kai)启。

MOS管导通电压