Image pickup apparatus with gain controlled output amplifier

Details Image pickup apparatus with gain controlled output amplifier Image pickup apparatus with gain controlled output amplifier

1982-05-19

1984-08-14

Chin, Tommy P.

Facsimile and static presentation processing

Facsimile

Recording apparatus

358212, 330254, H04N 514

Patent

active

044660189

ABSTRACT:
Solid-state image pickup apparatus, such as an MOS imager, has a two-dimensional array of picture element units each formed of a photo sensitive element and a gating element. The picture unit elements discharge a signal charge onto vertical and horizontal transmitting lines in response to vertical and horizontal scanning pulses. Then, a resulting signal current is used to develop an output video signal. In order to give the output video signal a good S/N ratio, a gain-controlled current amplifier is employed. In several embodiments, the gain-controlled amplifier includes first through fourth transistors with the base-emitter junctions of the first and second transistors and of the third and fourth transistors connected in series, with a constant current source coupled to the first transistor, controlled current sources connected to the second and third transistors, and a load device coupled to the fourth transistor. In other embodiments, the gain controlled amplifier is formed of first, second, and third current mirror circuits connected in a balanced-current arrangement. Electrically variable resistances, e.g., MOS transistors, are coupled to the output transistors of the first and second current mirror circuits to control the current gain.

REFERENCES:
patent: 4233630 (1980-11-01), Baker
patent: 4274113 (1981-06-01), Ohba
patent: 4355335 (1982-10-01), Imaide

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