Radiant energy – Photocells; circuits and apparatus – Photocell controlled circuit
Reexamination Certificate
1999-05-06
2001-05-01
Le, Que T. (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
Photocell controlled circuit
C250S2140AG, C330S277000, C330S307000
Reexamination Certificate
active
06225616
ABSTRACT:
RELATED APPLICATION
This application is related to Korean Application No. 98-18411, filed May 21, 1998, the disclosure of which is hereby incorporated herein by reference.
FIELD OF THE INVENTION
The present invention relates to integrated circuit devices, and more particularly to solid-state image pickup devices.
BACKGROUND OF THE INVENTION
Solid-state image pickup devices that utilize charge coupled devices (CCDs) can offer superior characteristics including high integration, low power consumption and/or low cost. Based on recent advances, such devices are now highly suitable for broadcast, video, monitoring and digital still camera applications. However, because such highly integrated devices typically generate relatively “weak” signals when capturing an image, it is often necessary to provide amplification of the “captured” signals without degradation or loss of fidelity. Accordingly, preferred signal amplification techniques are desired in highly integrated solid-state image pickup devices.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide improved solid-state image pickup devices.
It is another object of the present invention to provide solid-state image pickup devices with improved signal amplifiers therein.
These and other objects, advantages and features of the present invention are provided by an integrated circuit device (e.g., solid-state image pickup device) that provides a power/current gain to an input signal in a preferred manner using a source follower circuit that can have high input impedance. The source follower circuit comprises a drive transistor and a load transistor that are electrically connected in series (i.e., source-to-drain) between a first reference potential (e.g., Vdd) and a second reference potential (e.g., Vss). The input (e.g., gate electrode) of the drive transistor is electrically connected to an input terminal. The source follower circuit provides a high impedance path to an input signal Vin and a less than unity voltage gain at an output terminal (i.e., Vout<Vin). According to a preferred aspect of the present invention, the gain characteristics associated with the source follower circuit can be improved using a preferred load impedance control circuit.
The load impedance control circuit improves the voltage gain characteristics of the source follower circuit by automatically increasing the impedance of the load transistor when the output voltage increases in response to an increasing input voltage. In particular, as the output voltage increases, the on-state resistance of a pull-down transistor in the load impedance control circuit decreases. Using capacitive coupling, this decrease can provide an increase in the on-state resistance of the load transistor and a further increase in the output voltage and gain.
REFERENCES:
patent: 5872484 (1999-02-01), Hynecek
patent: 6147556 (2000-11-01), Nakano
Le Que T.
Luu Thanh X.
Myers Bigel & Sibley & Sajovec
Samsung Electronics Co,. Ltd.
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