Radiant energy – Photocells; circuits and apparatus – Photocell controlled circuit
Patent
1988-08-23
1990-08-28
Nelms, David C.
Radiant energy
Photocells; circuits and apparatus
Photocell controlled circuit
307311, H01V 4014
Patent
active
049527967
ABSTRACT:
In a semi-conducting integrated circuit, there is made a light detection circuit, the output signal of which can be used to counter manipulations by dishonest persons who undertake a decapsulation or a removal from the card when the integrated circuit is inserted in a bank type card, or even a depassivation of the upper protective layer of this integrated circuit, in order to reveal the secret functioning of the circuit or to modify its characteristics. The detector comprises a current generator delivering a current of limited intensity which flows into a reversed biased electronic junction. When the junction is subjected to light, the reverse current that can be allowed into the junction increases. Since the current generator is not capable of putting through stronger current, the voltage at the terminals of the junction drops. This drop in voltage is used as information that reveals the illumination.
REFERENCES:
patent: 3993569 (1976-11-01), Zinsmeyer et al.
patent: 4085411 (1978-04-01), Genesi
patent: 4282429 (1981-08-01), Galbraith
patent: 4454416 (1984-06-01), Gontowski, Jr. et al.
Fruhauf Serge
Sourgen Laurent
Nelms David C.
Plottel Roland
SGS-Thomson Microeleronics SA
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