Oscillation circuit with frequency dependent on incident light
AssigneeFujitsu Limited
InventorMitsuo Higuchi
Life of this patent
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Abstract
An oscillation circuit for providing oscillation frequencies which vary in response to the intensity of incident light rays. The circuit comprises a capacitance for storing charges and a charging circuit; said stored charges being decreased in response to an increase in the intensity of light rays incident on the capacitance; the charging circuit connected to the output of the oscillation circuit; the charging circuit being adapted to charge the capacitance. The oscillation circuit, when adapted to a bootstrap circuit in an EPROM erasable by means of ultraviolet rays, improves the write-in efficiency thereof.
Claims11
An oscillation circuit for providing an oscillation frequency which varies in response to the intensity of incident light rays, comprising
- a first capacitor for storing charges, said charges being decreased in response to increase in the intensity of the light rays incident on said first capacitor,
- a first waveform shaping circuit for converting the change of the voltage across said first capacitor to a rapidly changing waveform when said voltage across said capacitor crosses a first predetermined level,
- delay circuit for delaying said rapidly changing waveform outputted from said first waveform shaping circuit by at least one predetermined delay time,
- a second waveform shaping circuit for converting the change of the voltage outputted from said delay circuit to a rapidly changing waveform when said voltage outputted from said delay circuit crosses a second predetermined level, and
- a charging circuit connected to the output of said second waveform shaping circuit, for charging said first capacitor at a time corresponding to said predetermined delay time after said voltage across said capacitor falls below said first predetermined level.
Dependencies are inferred from the claim text.