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Although the LF357 is an
obsolete part, this circuit gives you an idea how to build a sensitive modulated light
detector with high ambient light immunity. The first section uses a 100mH
inductor as an efficient photodiode current to voltage conversion circuit.
The
second circuit performs much the same function but boosts the voltage generated by the
first circuit by a factor of X20 and filters out lower frequencies. Overall, the
conversion factor is about one volt per microwatt of light. Daylight noise is
typically less than 30mv peak to peak. The frequency response peaks at about 250KHz.
Although I have not tested it, I think the Texas Instruments TLC081 should work in this
application.
Click
on Drawing Below to view PDF version of Schematic
