Driving circuits of solenoid actuated devices

In a driving circuit of a solenoid actuated device of the type wherein a plunger is actuated by a solenoid coil, the driving circuit comprising a comparator having a first input supplied with an analog control signal representing an operating condition of a member to be controlled by the plunger, a second input, and an output;

• and a power amplifier circuit including an output amplifier in the form of an output transistor for supplying exciting current to the solenoid coil in response to the output of the comparator, the improvement comprising means coupled to said coil for detecting a voltage corresponding to said exciting current, positive feedback means, connected between said first input of said comparator and the output of one of said comparator and said output amplifier, and negative feedback means connected between said second comparator input and a junction between said detecting means and said coil, in order to provide ON-OFF control of said output transistor such that said exciting current comprises a current proportional to said analog control signal.