IIIH
US006724380B2
(12) United States Patent ao) Patent No.: us 6,724,380 B2
Lee (45) Date of Patent: Apr. 20,2004
(54) CONTRAST CONTROL CIRCUIT FOR DISPLAY APPARATUS
(75) Inventor: Choong-ho Lee, Pusan (KR)
(73) Assignee: Samsung SDI Co., Ltd., Kyungki-do (KR)
( * ) Notice: Subject to any disclaimer, the term ol this patent is extended or adjusted under 35 U.S.C. 154(b) by 366 days.
(21) Appl. No.: 09/842,664
(22) Filed: Apr. 27, 2001
(65) Prior Publication Data
US 2001/0035864 Al Nov. 1, 2001 (30) Foreign Application Priority Data
Apr. 28, 2000 (KR) 2000-22758
(51) Int. C I. G09G 5/00
(52) U.S. CI 345/211; 345/204
(58) Field of Search 345/211, 82, 89;
348/673; 323/282; 330/260
(56) References Cited
U.S. PATENT DOCUMENTS
3,649,847 A * 3/1972 Limberg 327/308
A contrast control circuit for a display apparatus includes first and second resistors, a first transistor, a second transistor, and a Darlington circuit. The first and second resistors, each have a first end connected to a positive supply voltage. The first transistor has an emitter connected to a second end ol the first resistor and a base to which the first voltage is input. The second transistor has an emitter connected to the second end ol the first resistor, a base connected to the second end ol the second resistor, and a collector connected to a negative supply voltage. The Darlington circuit is connected between the second voltage, the collector ol the first transistor, and the negative supply voltage, and operates such that the absolute value ol the second voltage is inversely proportional to the absolute value ol the first voltage.
4 Claims, 4 Drawing Sheets
