A.48% B.64% C.121% D.141%
當發(fā)光二極管發(fā)光時,兩端電壓為1.7V,則圖電路中的R應采用()
A.150Ω B.220Ω C.330Ω D.470Ω
A.1mV B.2.5mV C.10mV D.25mV