图题4.5.1 图解4.5.1 解(1)求A 由于ra>Ra,故ra可忽略,图题4.5.1的小信号等效电路如图解4.5.1所示。由图有 IR4=I[re+(1+B)R。] =+(1+B)R。;_1+(1+40)×0.18 R i=-(i+i)=-9.38i=gmV 1=9.38 V。=gmV。R-BiR=-9.38iR-401R=-49.38iR 49.38-9.38R=49.38 0.8V g×2≈8.3V V。=9.3 V8.3V v19.3V (2)求R R1=Ra+(Ra‖Ra)≈Ra3=5.1MQ 4.52电路如图题4.5.2所示。设两个FET的参数完全相同 试证明:(1)电压增益为 A [ra+(1+p)R1] 2ra+(1+p)(R1+R2 (2)输出电导为 R。n4+(1+)R1r4+(1+、 图题4.5.2 (3)如果R1=R2=R,试求Ay和R