2)空载时电压增益 bl barbe R e b2 Re2 Roll rb12 Blb R O Re R R2=Rh2llr+(1+ rol B1b(R21∥R2) 18.17 Tbe +(+BRellb 1,=An·A2=-18.09 (1+B)R2 R 2 0.996 13.93 The +(1+BR R+r18.17 [ (1 ) ] ( // ) //[ (1 ) ] 1 1 2 1 2 2 2 = − + + = − = + + • • b e e b b c i u i b b e e r R I I R R A R R r R    0.996 (1 ) (1 ) 2 2 2 = + + + = b e e e u r R R A   18.09 Au = Au1 • Au2 = − = −13.93 + = • i s i u s u R R R A A s s U R • Rb11 Rb12 I b1 • rbeRe1 I b1 •  Rc1 Rb2 I b2 • rbe I b2 •  Re 2 U o • + _ + _   Ri2 2)空载时电压增益