ACTIVE_LOAD

Published:2009/7/12 22:24:00 Author:May | From:SeekIC

National NSL4944 constantcurrent LED serves as cuffent source for collector resistor of Schmitt trigger to provide up to 12-V output at 40 mA for lamp load. When lamp andQ2 are off, most of LED current flows through 100-ohm resistor to determine circuit trip point of 2 V. When control signal saturates Q1, Q2 provides about 1 V for lamp to give some preheating and reduce starting cument surge.When control is above trip point, Q2 tums on and energizes lamp.-''Linear Applications, Vol.2,''National Semiconductor,Santa Clara, CA,1976,AN-153,P 3.



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