You might want to check out the datasheet for the Analog Devices AD795, this op-amp is often used as a photodiode pre-amp, and figures 42 and 46 might have just what you're looking for. Colin -- cdb, colin@btech-online.co.uk on 3/04/2009 Web presence: www.btech-online.co.uk Hosted by: www.1and1.co.uk/?k_id=7988359 -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist