Temperature compensating driver for a liquid crystal display
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United States of America Patent
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-
Feb 28, 1989
Grant Date -
N/A
app pub date -
Jan 21, 1986
filing date -
Jan 21, 1986
priority date (Note) -
Expired
status (Latency Note)
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Abstract
A circuit (8) is provided for driving the segment and back plane of a liquid crystal display. The circuit includes a plurality of transistors (Q1 to Q10) connected such that the base emitter junctions of the transistors are coupled in series between a voltage source and ground. The voltage at the emitter one of the transistors (Q3) is used to provide a first voltage (VLOW) for driving the LCD and a voltage at the emitter one of the other transistors (Q10) is used to provide the other voltage (VHIGH) for driving the LCD. Of importance, because the difference between the first and second voltages depends upon the voltage drop across a set of PN junctions, this difference in voltage varies with temperature. Specifically, the difference in voltage increases at low temperatures and decreases at high temperatures. In this way, the voltage used to drive the LCD is automatically compensated for temperature variations.
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