PURPOSE: To make the rise of a transistor switch circuit for driving a magnet steeper by such an arrangement wherein a current limiting circuit is provided in the circuit to make it possible to use a high power source voltage and raise its current and voltage higher without making a drive current excessively large.
CONSTITUTION: When an electric potential H is impressed on an input terminal 1 and electric potential L is impressed on an input terminal 2, a current flows through a transistor 8, magnet 11 and transistor 5-1. In proportion to this current, a voltage appears in a resistor 5-3. As this voltage exceeds the base saturated voltage of the transistors 5-2, the transistor 5-2 begins to conduct, and part of base current of the transistor 5-1 flows through the transistor 5-2. As the collector current (drive current of magnet 11) of the transistor 5-1 increases, the voltage of the resistor 5-3 becomes larger, therefor, the current flowing through the transistor 5-2 becomes larger. Due to this, the base current of the transistor 5-1 decreases and the transistor 5-1 becomes unable to flow a current exceeding a certain limit.
ASOU TOMIO
KUROKAWA KOUSHIROU
OBARA HIDEO
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