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Problem with AD8304 Log Amp Stability

Question asked by joelp on Dec 18, 2014
Latest reply on Jan 15, 2015 by jdobler

Having oscillation problems with an AD8304 setup to read the monitor current output from an APD voltage generator. Adding a few hundred ohms of series resistance helps eliminate an oscillation of ~1Mhz in the current range of 10uA to 100uA, but still have oscillation at ~40kHz for current <10uA. Currently setup per the datasheet with 750ohm and 1nF in series on input. I suspect I need to fine tune this and the driving impedance (or cover it up with series resistance). Looking for some guidance on how to go about this. In other words, try to keep zero at about the same frequency as the 750/1nf combination, maintain a certain resistance seen looking out from Input pin, etc..