PURPOSE:To prevent the generation of a pulse current when current directions are changed by connecting two constant current circuits between one couple of terminals with the opposite polarities and by connecting diodes across those constant current circuits, respectively. CONSTITUTION:Constant current circuits 15 and 16 are connected between terminals 12 and 14 in series with the opposite polarities, and in parallel to the circuits 15 and 16, diodes 21 and 22 are so connected that the constant current directions of the constant current circuits are the forward directins of the diodes. Further, the diodes 21 and 22 have a forward barrier voltage lower than that when the constant current circuits 15 and 16 operate as forward diodes, and also have short recovery time. For example, when the terminal 12 is negative and the terminal is positive, the circuit 15 never turns on as a diode and a current flows from the terminal 14 to the terminal 12 through the circuit 16 and diode 21. When the terminal 12 is positive and the terminal 14 is negative, on the other hand, a current flows from the circuit 15 through the diode 22; when current directions are changed, the charge storage amount of the diode 21 is less and its recovery time is short, suppressing the generation of a pulse current.
展开▼
