I am designing a driver circuit to drive a hydraulic proportional valve from an IC's PWM output. (IC is ATmega 2560). The coils on the valve draw approx 3Amps at %100 duty cycle with a power supply of 28v.
MOSFET's seem to be the way to accomplish this, thou I am struggling to find a 'safe' solution. The two primary methods I have so far come up with are;
A logic level MOSFET: (Please note R7 and R10 are the coil)
Or using an op-amp to boost the PWM signal and use a higher Vth MOSFET:
It seems the logic level version has a ~1v drop across Q3 when driving the coil, and I am concerned about that causing damage (heat, power loss etc)
Which of these (or any other way) would be the best way to provide control of an inductive load? (Or have I totally ended up with an incorrect design?)
(EDIT: Please note that protecting the IC from any single driver failure is paramount)