| 摘要 |
In a solenoid actuated device for controlling the oil supplied to a power steering unit of a motor car, a driving circuit is provided to pass current through the solenoid. The driving circuit comprises a comparator supplied with an analogue control signal proportional to the running speed of the motor car, a power amplifier including an output transistor which supplies exciting current to the solenoid coil in response to the output of the comparator. A positive feedback resistor is connected between the output of the comparator and the input thereof to which the analogue signal is applied, and a negative feedback resistor is connected between the output of the power amplifier another input of the comparator thereby ON-OFF controlling the output transistor to pass pulse current through the solenoid coil.
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