PROBLEM TO BE SOLVED: To obtain a driving circuit which is improved in braking ability by negatively feeding back the terminal voltage of an electromagnetic actuator to a driving current control circuit and, at the same time, controlling the driving current of the driving circuit by positively feeding back the terminal current to the driving current. SOLUTION: A driving circuit 100 incorporates a feedback circuit 34 and the feeding- back amount of a voltage varies depending upon the mutual conductance 1/Rf of a current source 31 (where, Rf is the internal impedance of the current source 31) and, in addition, depending upon the product of the converting sensitivity H of a current detector 40 and the inverse number Rf of the mutual conductance of the current source 31. When the mechanical resonance frequency is sufficiently higher than the cut-off frequency of the high-pass filter of a feedback circuit 34, a capacitor 41 is considered to be short-circuiting and an electromagnetic actuator can be braked at an arbitrary Q-value obtained by speed feedback by forming the feedback loop of the circuit 34 and calculating the Q-value, and deciding the feeding-back amount of the speed by selecting (H-1)Rf value. Therefore, a driving circuit having a high braking ability can be obtained.
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