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Photosensitive device with low power consumption
| Details |
Inventors: Delbruck, Tobias; Liu, Shih-Chii; Zahnd, Samual; Lichtsteiner, Patrick;
Assignee: Eidgenossische Technische Hochschule Zurich (Zurich, CH) Universitat Zurich (Zurich, CH)
Primary Examiner: Louie; Wai-Sing
Assistant Examiner:
Attorney, Agent or Firm: Dowden; Donald S. Cooper & Dunham LLP
A photosensitive device with a photodiode and an amplifier is disclosed. The diode is in series with a feedback transistor which forces the voltage derived from the photocurrent to be a logarithmic function of the light intensity. A current mirror is provided which controls the bias current to the amplifier to be proportional to the photocurrent. This arrangement ensures that the amplifier, just as the voltage derived from the photocurrent, becomes faster with increasing light intensity and therefore prevents an unnecessarily high power consumption at low light intensities. |
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DETAILED DESCRIPTION Hence, it is a general object of the invention to provide a device of this type with low power requirements.
Now, in order to implement these and still further objects of the invention, which will become more readily apparent as the description proceeds, the photosensitive device comprises at least one photodiode, at least one feedback element in series to said photodiode, wherein said feedback element is controlled to become increasingly conductive as a photocurrent through said photodiode increases, at least one amplifier amplifying a signal derived from the photocurrent and having a gain-bandwidth product, and control means for automatically controlling the gain-bandwidth product of the amplifier such that the gain bandwidth product increases with the photocurrent over at least part of a range of the photocurrent.
In another aspect of the invention, the photosensitive device comprises at least one photodiode, at least one feedback element in series to said photodiode, wherein said feedback element is controlled to become increasingly conductive as a photocurrent through said photodiode increases, an amplifier comprising at least one amplifier transistor, which amplifier transistor amplifies a signal derived from the photocurrent, and a current source generating a source-drain current of said amplifier transistor, which source-drain current increases with said photocurrent over at least part of a range of said photocurrent.
In a further aspect of the invention, the photosensitive device comprises at least one photodiode, at least one feedback element in series to said photodiode, wherein said feedback element is controlled to become increasingly conductive as a photocurrent through said photodiode increases, an amplifier amplifying a signal derived from the photocurrent and having a current input controlling a gain-bandwidth product of the amplifier, and a current mirror for generating a control current to said current input, wherein said control current is proportional to the photocurrent
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MEMS 
