Optical Sensor Amplifier
Original Publication Date: 1981-Aug-01
Included in the Prior Art Database: 2005-Feb-12
This circuit provides a down-level true logic signal at output 1 when paper is present in the sensor aperture. Phototransistor 3 is connected to the collector of transistor 5, which operates as a current sink. When current exceeds the sink capacity, the excess flows to the base of transistor 7, driving it strongly on.