ÐÀÑ×ÅÒ ÝËÅÌÅÍÒΠÂÛÑÎÊÎ×ÀÑÒÎÒÍÎÉ ÊÎÐÐÅÊÖÈÈ ÓÑÈËÈÒÅËÜÍÛÕ ÊÀÑÊÀÄΠÍÀ ÁÈÏÎËßÐÍÛÕ ÒÐÀÍÇÈÑÒÎÐÀÕ
         

ÐÀÑ×ÅÒ ÝËÅÌÅÍÒΠÂÛÑÎÊÎ×ÀÑÒÎÒÍÎÉ ÊÎÐÐÅÊÖÈÈ ÓÑÈËÈÒÅËÜÍÛÕ ÊÀÑÊÀÄΠÍÀ ÁÈÏÎËßÐÍÛÕ ÒÐÀÍÇÈÑÒÎÐÀÕ - ñòð. 4


;                                                                         (2.4)

.

                            à)                                                               á)

Ðèñ. 2.1

Ïðè çàäàííîì óðîâíå ÷àñòîòíûõ èñêàæåíèé

, âåðõíÿÿ ãðàíè÷íàÿ ÷àñòîòà
 ïîëîñû ïðîïóñêàíèÿ êàñêàäà ðàâíà:

*
=
.                                             (2.5)

Âõîäíîå ñîïðîòèâëåíèå êàñêàäà ìîæåò áûòü àïïðîêñèìèðîâàíî ïàðàëëåëüíîé RC öåïüþ [1]:

;                                  (2.6)

.                                   (2.7)

Ïðèìåð 2.1. Ðàññ÷èòàòü

,
,
,
 êàñêàäà, ïðèâåäåííîãî íà ðèñ. 2.1, ïðè èñïîëüçîâàíèè òðàíçèñòîðà ÊÒ610À [6](
= 5 Îì,
= 1 Îì,
= 0,0083 Ñèì,
= 4 ïÔ,
=160 ïÔ,
= 1 ÃÃö,
=120,
=0,95 À/Â,
= 0,99,
= 55 ìÀ), è óñëîâèé:
= 50 Îì;
= 0,9;
= 10.

Ðåøåíèå. Ïðè èçâåñòíûõ

 è
, â ñîîòâåòñòâèè ñ (2.1), èìååì:
= 10,5 Îì. Çíàÿ
, íàõîäèì:
= 13,3 Îì. Ïî ôîðìóëå (2.2) îïðåäåëèì:
= 1,03×10-9ñ. Ïîäñòàâëÿÿ èçâåñòíûå
 è
 â ñîîòíîøåíèå (2.5) ïîëó÷èì:
= 74,9 ÌÃö. Ïî ôîðìóëàì (2.6) è (2.7) îïðåäåëèì
= 196 ïÔ,
= 126 Îì.

2.2. ÏÐÎÌÅÆÓÒÎ×ÍÛÉ ÊÀÑÊÀÄ

Ïðèíöèïèàëüíàÿ ñõåìà êàñêàäà ïðèâåäåíà íà ðèñ. 2.2,à, ýêâèâàëåíòíàÿ ñõåìà ïî ïåðåìåííîìó òîêó - íà ðèñ. 2.2,á.

                                      à)                                                               á)

Ðèñ. 2.2

 ñîîòâåòñòâèè ñ [1] êîýôôèöèåíò óñèëåíèÿ êàñêàäà â îáëàñòè âåðõíèõ ÷àñòîò îïèñûâàåòñÿ âûðàæåíèåì:

,

ãäå   

;                                                                                       (2.8)




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