利盈娱乐(中国)创新平台有限公司

场效应(ying)管的作用：

场效应管是(shi)场效(xiao)应(ying)晶体管（Field Effect Transistor,FET）的(de)简(jian)称。它属于(yu)电(dian)压控(kong)制型半导体器件，具有输(shu)入电(dian)阻高、噪声小(xiao)、功耗(hao)低、没(mei)有二次击穿现象、安全(quan)工(gong)作区(qu)域宽、受温(wen)度和(he)辐射影响(xiang)小(xiao)等优(you)点，特别适用(yong)于(yu)高灵敏(min)度和(he)低噪声的(de)电(dian)路，现已成(cheng)为普通晶体管的(de)强大竞争者。

三极管和场效应管的主要区别在于三极管的放大或者开关功能依赖基极的电流分量。场效应管的放大和开关功能依赖于栅极的电压分量。其他还有开关时间特性的区别，一般晶体三极管大电流的开关速度远比不上场效应管。
三(san)极(ji)(ji)(ji)管(guan)(guan)(guan)是(shi)(shi)靠(kao)载流子(zi)(zi)的(de)(de)(de)(de)(de)(de)(de)(de)运动(dong)(dong)来(lai)工作的(de)(de)(de)(de)(de)(de)(de)(de)，以(yi)npn管(guan)(guan)(guan)射(she)极(ji)(ji)(ji)跟随器为(wei)(wei)例，当(dang)基(ji)极(ji)(ji)(ji)加不加电(dian)(dian)(dian)(dian)(dian)压(ya)时(shi)(shi)，基(ji)区(qu)(qu)(qu)和发(fa)射(she)区(qu)(qu)(qu)组成的(de)(de)(de)(de)(de)(de)(de)(de)pn结(jie)为(wei)(wei)阻止(zhi)多子(zi)(zi)（基(ji)区(qu)(qu)(qu)为(wei)(wei)空(kong)穴，发(fa)射(she)区(qu)(qu)(qu)为(wei)(wei)电(dian)(dian)(dian)(dian)(dian)子(zi)(zi)）的(de)(de)(de)(de)(de)(de)(de)(de)扩散运动(dong)(dong)，在(zai)此(ci)pn结(jie)处会感应(ying)出由发(fa)射(she)区(qu)(qu)(qu)指向(xiang)基(ji)区(qu)(qu)(qu)的(de)(de)(de)(de)(de)(de)(de)(de)静电(dian)(dian)(dian)(dian)(dian)场（即内建(jian)电(dian)(dian)(dian)(dian)(dian)场），当(dang)基(ji)极(ji)(ji)(ji)外(wai)加正电(dian)(dian)(dian)(dian)(dian)压(ya)的(de)(de)(de)(de)(de)(de)(de)(de)指向(xiang)为(wei)(wei)基(ji)区(qu)(qu)(qu)指向(xiang)发(fa)射(she)区(qu)(qu)(qu)，当(dang)基(ji)极(ji)(ji)(ji)外(wai)加电(dian)(dian)(dian)(dian)(dian)压(ya)产生的(de)(de)(de)(de)(de)(de)(de)(de)电(dian)(dian)(dian)(dian)(dian)场大于(yu)内建(jian)电(dian)(dian)(dian)(dian)(dian)场时(shi)(shi)，基(ji)区(qu)(qu)(qu)的(de)(de)(de)(de)(de)(de)(de)(de)载流子(zi)(zi)（电(dian)(dian)(dian)(dian)(dian)子(zi)(zi)）才有可(ke)能(neng)从(cong)基(ji)区(qu)(qu)(qu)流向(xiang)发(fa)射(she)区(qu)(qu)(qu)，此(ci)电(dian)(dian)(dian)(dian)(dian)压(ya)的(de)(de)(de)(de)(de)(de)(de)(de)最小值即pn结(jie)的(de)(de)(de)(de)(de)(de)(de)(de)正向(xiang)导(dao)通电(dian)(dian)(dian)(dian)(dian)压(ya)（工程上一般认为(wei)(wei)0.7v）。但此(ci)时(shi)(shi)每个(ge)pn结(jie)的(de)(de)(de)(de)(de)(de)(de)(de)两(liang)侧(ce)都(dou)会有电(dian)(dian)(dian)(dian)(dian)荷(he)存在(zai)，此(ci)时(shi)(shi)如(ru)果集成电(dian)(dian)(dian)(dian)(dian)极(ji)(ji)(ji)-发(fa)射(she)极(ji)(ji)(ji)加正电(dian)(dian)(dian)(dian)(dian)压(ya)，在(zai)电(dian)(dian)(dian)(dian)(dian)场作用下，发(fa)射(she)区(qu)(qu)(qu)的(de)(de)(de)(de)(de)(de)(de)(de)电(dian)(dian)(dian)(dian)(dian)子(zi)(zi)往(wang)基(ji)区(qu)(qu)(qu)运动(dong)(dong)（实际(ji)上都(dou)是(shi)(shi)电(dian)(dian)(dian)(dian)(dian)子(zi)(zi)的(de)(de)(de)(de)(de)(de)(de)(de)反(fan)方向(xiang)运动(dong)(dong)），由于(yu)基(ji)区(qu)(qu)(qu)宽度很小，电(dian)(dian)(dian)(dian)(dian)子(zi)(zi)很容易越过(guo)(guo)基(ji)区(qu)(qu)(qu)到(dao)达(da)集电(dian)(dian)(dian)(dian)(dian)区(qu)(qu)(qu)，并(bing)与此(ci)处的(de)(de)(de)(de)(de)(de)(de)(de)PN的(de)(de)(de)(de)(de)(de)(de)(de)空(kong)穴复合（靠(kao)近(jin)集电(dian)(dian)(dian)(dian)(dian)极(ji)(ji)(ji)），为(wei)(wei)维持平(ping)衡(heng)，在(zai)正电(dian)(dian)(dian)(dian)(dian)场的(de)(de)(de)(de)(de)(de)(de)(de)作用下集电(dian)(dian)(dian)(dian)(dian)区(qu)(qu)(qu)的(de)(de)(de)(de)(de)(de)(de)(de)电(dian)(dian)(dian)(dian)(dian)子(zi)(zi)加速外(wai)集电(dian)(dian)(dian)(dian)(dian)极(ji)(ji)(ji)运动(dong)(dong)，而空(kong)穴则为(wei)(wei)pn结(jie)处运动(dong)(dong)，此(ci)过(guo)(guo)程类似(si)一个(ge)雪崩过(guo)(guo)程。集电(dian)(dian)(dian)(dian)(dian)极(ji)(ji)(ji)的(de)(de)(de)(de)(de)(de)(de)(de)电(dian)(dian)(dian)(dian)(dian)子(zi)(zi)通过(guo)(guo)电(dian)(dian)(dian)(dian)(dian)源回到(dao)发(fa)射(she)极(ji)(ji)(ji)，这就(jiu)是(shi)(shi)晶体管(guan)(guan)(guan)的(de)(de)(de)(de)(de)(de)(de)(de)工作原(yuan)理。三(san)极(ji)(ji)(ji)管(guan)(guan)(guan)工作时(shi)(shi)，两(liang)个(ge)pn结(jie)都(dou)会感应(ying)出电(dian)(dian)(dian)(dian)(dian)荷(he)，当(dang)做开关管(guan)(guan)(guan)处于(yu)导(dao)通状态时(shi)(shi)，三(san)极(ji)(ji)(ji)管(guan)(guan)(guan)处于(yu)饱和状态，如(ru)果这时(shi)(shi)三(san)极(ji)(ji)(ji)管(guan)(guan)(guan)截至，pn结(jie)感应(ying)的(de)(de)(de)(de)(de)(de)(de)(de)电(dian)(dian)(dian)(dian)(dian)荷(he)要(yao)恢复到(dao)平(ping)衡(heng)状态，这个(ge)过(guo)(guo)程需(xu)要(yao)时(shi)(shi)间。

总结：

1．MOSFET温度(du)稳定(ding)性好，而三(san)极管(guan)受(shou)温度(du)影响较大，因此环境温度(du)变化(hua)较的(de)场合下，采用(yong)MOSFET更合适(shi)。

2．用来(lai)放(fang)大信号(hao)时，三极管输入端的发射结为(wei)正向偏置。输入阻(zu)抗(kang)较小(xiao)。而MOSFET输入阻(zu)抗(kang)极高，因此MOSFETＴ放(fang)大级(ji)对前级(ji)的放(fang)大能力影响极小(xiao)。

3．MOSFET的输入(ru)电(dian)(dian)阻极高，所以一旦(dan)栅极上感应(ying)少量电(dian)(dian)荷。就管(guan)。因(yin)此(ci)使用ＭＯＳ管(guan)时要(yao)特别小心。尤其是焊接(jie)ＭＯＳ管(guan)时，电(dian)(dian)烙(luo)铁外壳要(yao)良好接(jie)地。管(guan)子存放时，应(ying)使ＭＯＳ管(guan)栅极与源极短接(jie)，避免(mian)栅极悬空。

4．三(san)极(ji)(ji)管由于(yu)发(fa)射区和集(ji)(ji)电区结(jie)构上的(de)不对称，所以正常(chang)使用时．发(fa)射极(ji)(ji)和集(ji)(ji)电极(ji)(ji)是不能(neng)(neng)互(hu)换(huan)的(de)。而MOSFET在(zai)(zai)结(jie)构上是对称的(de)。所以源极(ji)(ji)和漏极(ji)(ji)可以互(hu)换(huan)使用。但要注意(yi)。分立的(de)MOSFET．有时已将衬底(di)和源极(ji)(ji)在(zai)(zai)管内短(duan)接(jie)，源极(ji)(ji)和漏极(ji)(ji)就不能(neng)(neng)互(hu)换(huan)使用了。

5．场效应管(guan)放大电(dian)路最(zui)大最(zui)突出的(de)特点(dian)是．共(gong)(gong)源、共(gong)(gong)漏和(he)共(gong)(gong)栅电(dian)路的(de)输(shu)入(ru)电(dian)阻高于(yu)(yu)相应的(de)共(gong)(gong)发(fa)射极、共(gong)(gong)集电(dian)极和(he)共(gong)(gong)基(ji)极电(dian)路的(de)输(shu)入(ru)电(dian)阻。此(ci)外(wai)，场效应管(guan)还有噪声低、温度(du)稳定性好、抗辐射能力(li)强等(deng)优(you)于(yu)(yu)三极管(guan)的(de)特点(dian)，而且便(bian)于(yu)(yu)集成。

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