Radiant energy – Photocells; circuits and apparatus – Photocell controlled circuit
Patent
1992-03-03
1993-04-20
Nelms, David C.
Radiant energy
Photocells; circuits and apparatus
Photocell controlled circuit
307201, 250551, H01J 3150
Patent
active
052045218
ABSTRACT:
An integrated, optoelectronic, variable thresholding neuron implemented monolithically in a GaAs integrated circuit and exhibiting high differential optical gain and low power consumption. Two alternative embodiments each comprise an LED monolithically integrated with a detector and two transistors. One of the transistors is responsive to a bias voltage applied to its gate for varying the threshold of the neuron. One embodiment is implemented as an LED monolithically integrated with a double heterojunction bipolar phototransistor (detector) and two metal semiconductor field-effect transistors (MESFET's) on a single GaAs substrate and another embodiment is implemented as an LED monolithically integrated with three MESFET's (one of which is an optical FET detector) on a single GaAs substrate. The first noted embodiment exhibits a differential optical gain of 6 and an optical switching energy of 10 pJ. The second embodiment has a differential optical gain of 80 and an optical switching energy or 38 pJ. Power consumption is 2.4 mW and 1.8 mW, respectively. Input "light" power needed to turn on the LED is 2 .mu.W and 54 nW, respectively. In both embodiments the detector is in series with a biasing MESFET and saturates the other MESFET upon detecting light above a threshold level. The saturated MESFET turns on the LED. Voltage applied to the biasing MESFET gate, controls the threshold.
REFERENCES:
patent: 4951239 (1990-08-01), Andes et al.
patent: 4956564 (1990-09-01), Holler et al.
patent: 5130563 (1992-07-01), Nabet et al.
Kim Jae H.
Lin Steven H.
Psaltis Demetri
Davenport T.
Jones Thomas H.
Kusmiss John H.
Miller Guy M.
Nelms David C.
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