The application of the voltage follower R1 R R,+ r R,∥/R L DRI=D U,≠D R1+R2∥R 足1 2 R2 R U R 2 R+rThe application of the voltage follower R o R R R L     1 2 2 2 1 + = = = 1 1 2 2 1 1 2 2 1        + = = + = o L L R o R R R R R R R R L // //