| 摘要 |
A circuit is disclosed producing an output voltage which varies with temperature in a manner matching the manner in which the voltage required to maintain a given light transmission of a liquid crystal display (LCD) segment varies with temperature. The LCD segment is connected across a high input impedance amplifier so as to provide capacitive negative feedback. Ganged electronic switches connect equal value capacitors alternately to the amplifier output and (through an input capacitor) the amplifier input. The switches are driven at the LCD multiplexing frequency. Any charge on one of the two equal value capacitors causes the amplifier to produce a greater charge of opposite sign on the other of them and this develops a voltage across the LCD segment which changes its capacitance until a stable situation is reached in which its capacitance equals that of the input capacitor and the gain of the amplifier is unity. Any change in the LCD capacitance produced by changing temperature causes a change in the voltage across the two equal value capacitors which in turn alters the capacitance of the LCD segment back to the value equal to that of the input capacitor. Consequently the capacitance, and thus the light transmission, of the segment is changed back to the value existing before the temperature change.
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