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E C

E C 、 R 和 T 1 ­ 构成镜像恒流源的参考回路. I R 称为参考电流. E C. R. I R. I R. I C2. I B1. I C1. I B2. T 1. T 2. r o. 输出电流 I C2 与参考电流 I R 是镜像关系. 基本镜像恒流源. r o ≈ r ce2 ≈∞. U BE1 = U BE2 = U BE. 若 β 1 = β 2 = β. I B1 = I B2 = I B 、 I C1 = I C2 = I C. 接放大器. 2 I B. 当 β >>1 时，可得. + U BEQ -.

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E C

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  1. EC 、R和T1­构成镜像恒流源的参考回路 IR称为参考电流 EC R IR IR IC2 IB1 IC1 IB2 T1 T2 r o 输出电流IC2与参考电流IR是镜像关系 基本镜像恒流源 ro ≈rce2≈∞ UBE1= UBE2= UBE 若β1=β2=β IB1=IB2=IB 、IC1=IC2=IC 接放大器 2IB 当β>>1时，可得 + UBEQ - 相对误差

  2. EC R IR IC(n+1) IC3 IC4 IC2 (n+1)IB IB1 IB4 IB3 IBn IB2 T1 Tn T4 T3 T2 相对误差

  3. EC R IR IB3 T3 IB1 IC1 IB2 IC2 IE3 T1 T2 + UBEQ - r o ro ≈rce2≈∞ 2．精密镜像恒流源 β1=β2=β3=β>>1 设T1～T3的参数相同 UBE1=UBE2=UBE IC1=IC2 由于电路中接了共集电极管T3，对分流电流IB3的放大作用，从而使误差减小了（1+β）倍，精度提高了（1+β）倍。 相对误差

  4. EC R IR 2IB IC1 T1 T2 IR IC2 IB1 IB1 IB2 IB2 T3 T4 3．高输出阻抗串接镜像恒流源 (cascade) β1=β2=β3=β4>>1 UBE1=UBE2=UBE3=UBE4=UBE + UBEQ - 相对误差 + UBEQ - 思考：对照P202式4-5-17，为何不同？

  5. EC IR IR IC2 IC2 R T2 + UBEQ - 2IB3 IB3 IC1 IE2 IC3 IB1 IB3 T3 T1 T2 + UBEQ - 4．威尔逊（Wilson）恒流源（反馈型，高输出阻抗精密恒流源） 设Tl~T3完全匹配 IR=IC1+IB2 = IC1+IC2/β ( UBE1= UBE3= UBE) IC1=IC3 IC3=IE2 -2IB =IE2 -2IC3 /β IC2

  6. EC Rc IC2 Rb + uo - EC EC + UBEQ - EC T3 R R IR IR IR IC2 IC2 R T1 T1 T2 T2 T2 EC IC1 R IR T3 IC2 T1 T2 T3 T4 T1 T2 r o 模拟集成电路中的偏置电路，也可作为放大电路的有源负载，又可组成基本的电流传输器

  7. EC 接放大器 IR IC2 R IR T1 T2 IE1 IE2 IE1 IC2 IE2 R1 R2 5．比例恒流源 UB1=UB2= UB UB 其中，R1'=R //（R1+ rbe1）

  8. EC 接放大器 R IR IC2 T1 T2 UB IE1 IE2 R1 R2 6．微恒流源（Widlar恒流源） R1＝0

  9. EC 接放大器 EC EC R IR T2 T2 T3 T3 IC2 R R IR IR T1 T2 IC2 + uo - + uo - EC + ui - + ui - T1 T1 IR rce2 电压增益大大提高 提供大的集电极交流负载 提供稳定的直流电流，稳定静态工作点 有源负载共射放大器 有源负载放大器从电流源分析

  10. EC T1 RL R IR io T3 IR rce2 T2 R1 R2 -EE -EE r o + ui - 有源负载射极跟随器 + uo -

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