Post History

<h2>Partial answer awaiting more specs</h2>

Your question can't really be answered until we know how accurate the resulting solenoid drive levels need to be relative to the 0-10 V input signals, and how fast the system must respond.  However, here are a few observations in the mean time:<ol>

<p><li><b>Use a microcontroller already!</b>  There are lots of good reasons analog circuits like this went out 20 years ago.  There are many cheap and available micros that come with 12 bit A/Ds and PWM generators built in.  There would be three analog inputs to the micro: The two control signals and a reference voltage.  The micro would be running directly from the battery, which would also be the positive voltage reference for the A/D.  The rest is math deciding what the pulse width needs to be each PWM cycle.

<p><li>A TL081 is totally inappropriate in this application.  See its datasheet for power supply range and headroom.

<li>The coils of solenoids are inherently floating.  You are going thru some trouble to convert a low side PWM signal to a high side drive.  The solenoid will work just fine with one input tied to power and the other to a low side PWM drive.  Of course if someone decided to tie one side of the solenoid to ground externally where you can't control it, then you have to deal with this.  However, that should at least prompt a discussion of the higher level architecture.

<p><li>If the digital PWM signal goes from ground to the battery voltage, then you can use that to drive a P-channel FET as a high side driver directly.

<p><li>D1 makes no sense as shown.  The anode should go to ground, not the right side of L1.  Also, at these voltages it's a no-brainer to make it Schottky.

<p><li>Depending on the accuracy you really need, you might want to use synchronous rectification.  There are plenty of micros with PWM generators that have complementary outputs with the appropriate dead time controls.  Synchronous rectification removes the diode drop from the off-time output voltage as a source of error.  You could compensate for some of that in the math when the solenoid is run in continuous mode.  At low drive levels it will go to discontinuous mode, in which case it will be much more difficult to know the off-time solenoid drive voltage open-loop.

</p></ol>