As a possible alternative to the opto have you looked at the GMR isolators
from NVE - lower power, higher frequency (up to 110MHz !)  & without the
thermal and aging considerations of optos. Also direct digital output at
either 3.3 or 5V levels. But they do cost a bit more! May be an overkill
for this project but look to be very useful devices.

Richard P



Looking for suggestions for a PWM driver.
Scope of work includes using a pic for PWM (20kHz),
a single channel galvanic opto-isolators with digital
output used on the high side.  Thereafter the use of
2 orders of filtering, then a FET circuit to drive a
24VDC 800mA proportional valve.  I am considering the
following components: pic, Micrel's MIC5021, LT1013
op-amp, and a SFP9520 FET.  The pic's (16C series)
PWM and PID routines are drafted.  I could really
use your feedback on any portion of this new project.
Tx, slewrate

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