On-chip light sensor
First Claim
1. A circuit for providing an electrical signal to indicate when incident light exceeds or falls below a certain level of brightness, comprising:
- a photodiode for detecting incident light and generating an input current;
a first current mirror for receiving and amplifying said input current and delivering the amplified input current to an intermediate node;
a current source for providing a reference current;
a second current mirror for receiving and amplifying said reference current and for delivering the amplified reference current to said intermediate node; and
an inverter for receiving the current from said intermediate node and for changing state at its output when said amplified input current exceeds said amplified reference current.
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Abstract
A brightness sensing circuit for providing a binary electrical signal for indicating whether incident light exceeds a certain brightness. The circuit'"'"'s light detector is a photodiode, whose output is amplified by a first current mirror. The circuit has a reference current source, whose output is amplified by a second current mirror. Both currents are delivered to a common node, whose voltage level transitions from low to high when the amplified input current exceeds the amplified reference current. This node is connected to the gate input of a CMOS inverter, which provides a binary output.
95 Citations
20 Claims
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1. A circuit for providing an electrical signal to indicate when incident light exceeds or falls below a certain level of brightness, comprising:
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a photodiode for detecting incident light and generating an input current; a first current mirror for receiving and amplifying said input current and delivering the amplified input current to an intermediate node; a current source for providing a reference current; a second current mirror for receiving and amplifying said reference current and for delivering the amplified reference current to said intermediate node; and an inverter for receiving the current from said intermediate node and for changing state at its output when said amplified input current exceeds said amplified reference current. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A monolithic device which includes a deformable mirror and a circuit for indicating the brightness level of light incident on the mirror, comprising:
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at least one micro-mechanical mirror element on said device; and a shut-off circuit on said monolithic device comprising a photodiode for receiving a portion of said light incident on said monolithic device and providing an input current, a first current mirror for amplifying said input current to an intermediate node, a current source for providing a reference current, a second current mirror for amplifying said reference current to said intermediate node, and an inverter connected to said intermediate node for providing a binary output depending on the voltage at said intermediate node. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
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20. A method of measuring incident light comprising;
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generating an input current based on the level of said incident light; amplifying said input current; providing a reference current; outputting a first signal level when the magnitude of said amplified input current exceeds the magnitude of said reference current; and outputting a second signal level when the magnitude of said reference current exceeds the magnitude of said amplified input current.
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Specification