功率信號源是指(zhi)集信(xin)號發生器與功(gong)(gong)率(lv)放大器為一(yi)體的(de)電(dian)(dian)子測量(liang)儀器，它具(ju)有高(gao)電(dian)(dian)壓(ya)、大功(gong)(gong)率(lv)的(de)特(te)點(dian)，在電(dian)(dian)子實(shi)驗室中能夠幫助(zhu)用來驅動壓(ya)電(dian)(dian)陶瓷、換能器以(yi)及電(dian)(dian)磁線圈(quan)等，可以(yi)有效的(de)幫助(zhu)電(dian)(dian)子工程師解(jie)決驅動負(fu)載和放大功(gong)(gong)率(lv)的(de)問題。

　　輸(shu)(shu)(shu)入電(dian)(dian)(dian)(dian)阻(zu)(zu)是(shi)用來衡量放(fang)大(da)(da)(da)器(qi)對信(xin)(xin)(xin)(xin)號源(yuan)的(de)(de)影響的(de)(de)一(yi)個性能指標。輸(shu)(shu)(shu)入電(dian)(dian)(dian)(dian)阻(zu)(zu)越(yue)(yue)大(da)(da)(da)，表明放(fang)大(da)(da)(da)器(qi)從信(xin)(xin)(xin)(xin)號源(yuan)取(qu)的(de)(de)電(dian)(dian)(dian)(dian)流越(yue)(yue)小(xiao)，放(fang)大(da)(da)(da)器(qi)輸(shu)(shu)(shu)入端得到的(de)(de)信(xin)(xin)(xin)(xin)號電(dian)(dian)(dian)(dian)壓(ya)也越(yue)(yue)大(da)(da)(da)，即(ji)信(xin)(xin)(xin)(xin)號源(yuan)電(dian)(dian)(dian)(dian)壓(ya)衰減(jian)的(de)(de)少。理論基礎(chu)：Us=（Rs+Ri）×I。Rs為信(xin)(xin)(xin)(xin)號源(yuan)內阻(zu)(zu)，Ri為放(fang)大(da)(da)(da)器(qi)輸(shu)(shu)(shu)入電(dian)(dian)(dian)(dian)阻(zu)(zu)。因(yin)此作(zuo)為測量信(xin)(xin)(xin)(xin)號電(dian)(dian)(dian)(dian)壓(ya)的(de)(de)示波器(qi)、電(dian)(dian)(dian)(dian)壓(ya)表等儀器(qi)的(de)(de)放(fang)大(da)(da)(da)電(dian)(dian)(dian)(dian)路(lu)應當具有較大(da)(da)(da)的(de)(de)輸(shu)(shu)(shu)入電(dian)(dian)(dian)(dian)阻(zu)(zu)。對于一(yi)般的(de)(de)放(fang)大(da)(da)(da)電(dian)(dian)(dian)(dian)路(lu)來說，輸(shu)(shu)(shu)入電(dian)(dian)(dian)(dian)阻(zu)(zu)當然(ran)是(shi)越(yue)(yue)大(da)(da)(da)越(yue)(yue)好。如果(guo)想從信(xin)(xin)(xin)(xin)號源(yuan)取(qu)得較大(da)(da)(da)的(de)(de)電(dian)(dian)(dian)(dian)流，則應該使(shi)放(fang)大(da)(da)(da)器(qi)具有較小(xiao)的(de)(de)輸(shu)(shu)(shu)入電(dian)(dian)(dian)(dian)阻(zu)(zu)。

　　圖：ATG-2031功率信號源指標參數

　　輸(shu)(shu)出(chu)(chu)電(dian)(dian)(dian)阻用來(lai)衡(heng)量放大(da)(da)(da)(da)器在(zai)不同負載(zai)條(tiao)(tiao)件下維(wei)持(chi)輸(shu)(shu)出(chu)(chu)信(xin)號(hao)(hao)電(dian)(dian)(dian)壓(ya)（或(huo)電(dian)(dian)(dian)流）恒(heng)定能(neng)力的(de)強弱(ruo)，稱為其帶負載(zai)能(neng)力。當放大(da)(da)(da)(da)器將放大(da)(da)(da)(da)了(le)的(de)信(xin)號(hao)(hao)輸(shu)(shu)出(chu)(chu)給(gei)負載(zai)電(dian)(dian)(dian)阻RL時(shi)，對負載(zai)RL來(lai)說，放大(da)(da)(da)(da)器可(ke)(ke)以等效為具有內阻Ro的(de)信(xin)號(hao)(hao)源，由這個信(xin)號(hao)(hao)源向RL提供輸(shu)(shu)出(chu)(chu)信(xin)號(hao)(hao)電(dian)(dian)(dian)壓(ya)和(he)輸(shu)(shu)出(chu)(chu)信(xin)號(hao)(hao)電(dian)(dian)(dian)流。Ro稱為放大(da)(da)(da)(da)器的(de)輸(shu)(shu)出(chu)(chu)電(dian)(dian)(dian)阻，它(ta)是從放大(da)(da)(da)(da)器輸(shu)(shu)出(chu)(chu)端向放大(da)(da)(da)(da)器本(ben)身看入的(de)交流等效電(dian)(dian)(dian)阻。如(ru)果輸(shu)(shu)出(chu)(chu)電(dian)(dian)(dian)阻Ro很小，滿足(zu)Ro<條(tiao)(tiao)件，則當RL在(zai)較(jiao)大(da)(da)(da)(da)范圍(wei)內變化時(shi)，就可(ke)(ke)基本(ben)維(wei)持(chi)輸(shu)(shu)出(chu)(chu)信(xin)號(hao)(hao)電(dian)(dian)(dian)壓(ya)的(de)恒(heng)定。反之(zhi)，如(ru)果輸(shu)(shu)出(chu)(chu)電(dian)(dian)(dian)阻Ro很大(da)(da)(da)(da)，滿足(zu)Ro>>RL條(tiao)(tiao)件，則當RL在(zai)較(jiao)大(da)(da)(da)(da)范圍(wei)內變化時(shi)，就可(ke)(ke)維(wei)持(chi)輸(shu)(shu)出(chu)(chu)信(xin)號(hao)(hao)電(dian)(dian)(dian)流的(de)恒(heng)定。如(ru)手機(ji)電(dian)(dian)(dian)池，它(ta)的(de)內阻可(ke)(ke)以等效看作(zuo)輸(shu)(shu)出(chu)(chu)電(dian)(dian)(dian)阻，用了(le)幾年后，內阻高了(le)，也就要報廢了(le)，因為帶不動(dong)外面(mian)的(de)東西(xi)了(le)。

　　電(dian)壓放大(da)(da)和(he)(he)互阻放大(da)(da)電(dian)路(lu)，即輸出為(wei)電(dian)壓信(xin)號的放大(da)(da)電(dian)路(lu)，Ro越小，負載RL對(dui)的變化對(dui)輸出信(xin)號Vo的影響越小。而(er)且只要負載RL足夠大(da)(da)，信(xin)號輸出功率一般(ban)較低，能耗也較低。多用(yong)于(yu)信(xin)號的前置放大(da)(da)和(he)(he)中(zhong)間級放大(da)(da)。對(dui)于(yu)一般(ban)的放大(da)(da)電(dian)路(lu)來說，輸出電(dian)阻當然越小越好(hao)。

　　電(dian)(dian)(dian)(dian)流放(fang)(fang)大(da)和互導(dao)放(fang)(fang)大(da)電(dian)(dian)(dian)(dian)路(lu)，即輸(shu)(shu)出為電(dian)(dian)(dian)(dian)流信號(hao)的(de)放(fang)(fang)大(da)電(dian)(dian)(dian)(dian)路(lu)，與(yu)受控電(dian)(dian)(dian)(dian)流源并聯(lian)的(de)Ro越大(da)，負載RL的(de)變化(hua)對輸(shu)(shu)出電(dian)(dian)(dian)(dian)流Io的(de)影響越小。則與(yu)前兩種相比當(dang)供(gong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)源相同時，可(ke)(ke)得到較大(da)輸(shu)(shu)出電(dian)(dian)(dian)(dian)流信號(hao)，所(suo)以功(gong)率可(ke)(ke)能(neng)到達較大(da)的(de)值，對供(gong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)源的(de)能(neng)耗較大(da)。通常用(yong)于電(dian)(dian)(dian)(dian)子系(xi)統的(de)輸(shu)(shu)出級，可(ke)(ke)作為各種輸(shu)(shu)出物理變量變換器（如音響系(xi)統的(de)揚(yang)聲器，動力系(xi)統的(de)電(dian)(dian)(dian)(dian)動機(ji)等）的(de)驅動電(dian)(dian)(dian)(dian)路(lu)。

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