Fast_optically_isolated_transistor_or_switch

Published:2009/7/22 22:28:00 Author:Jessie | From:SeekIC

This circuit is similar to that of Fig. 9-54, but it has better ac response. The cathode of D2 is returned to a separate positive supply, rather than to the collector of Q1, which eliminates the added collector-to-base capacitance of D2. With this circuit, a 40-V 1-A load can be switched in 500 ns. Any photosensitive diode can be used for D2, instead of the optoisolator, to make a light-activated switch.



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