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US 4,047,049 AGranted
Drive circuit with constant current output
AssigneeLitton Systems, Inc.
InventorsFred William Erickson, Roy Hiroshi Nakahara
Life of this patent
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Abstract
A constant current drive circuit that can be driven directly from the output of a shift register which can find use, for example, as a constant current source for a light emitting diode (LED) to ensure uniform birghtness throughout a display surface that includes a plurality of LEDs.
Claims10
A constant current drive circuit comprising:
- (a) first electrical energy source means supplying a first electrical energy level output,
- (b) second electrical energy source means responsive to said first electrical energy level output and supplying a selectively variable second energy level output,
- (c) a resistor connected in electrical series with said first electrical energy source means and responsive to said first electrical energy level output,
- (d) bistable control means including triode means responsive to said first electrical energy level output through said resistor and to said second electrical energy level output, said bistable triode means providing a third electrical energy level output having a constant current determinable by said selectively variable second energy level output, and
- (e) signal generating means selectively enabling and disabling said triode means so that the constant current drive circuit is selectively enabled and disabled.
2 more elements
Dependencies are inferred from the claim text.