If I supply a negative reference current, can the ADL5304 be used to measure negative input current? The datasheet doesn't mention anything regarding this, but does not say it cannot be done.
No, this won't work, current needs to flow into the collector of the measurement/reference transistor for the ADL5304 to work correctly.
Have you looked at using one of the current mirrors, ADL5315 or ADL5317, to reverse the polarity of the current?
Hope this helps,
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