The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Mar. 06, 1979
Filed:
Mar. 22, 1978
Leopold A Harwood, Bridgewater, NJ (US);
Erwin J Wittmann, North Plainfield, NJ (US);
RCA Corporation, New York, NY (US);
Abstract
Brightness control apparatus in a video system employing a sample and hold circuit including a charge storage capacitor. The sample and hold circuit forms a closed control loop with a signal processing channel, and is keyed during periodic blanking intervals of the video signal to sample the magnitude of a reference voltage and a brightness representative blanking level of the video signal. The sample and hold circuit provides an output control signal indicative of the voltage difference between the reference voltage and the blanking level. The control signal is applied to the signal channel for translating the blanking level in a direction to minimize the voltage difference, so that a desired relationship between the reference voltage and the blanking level is preserved. In a preferred embodiment, a diode coupled between a sampling transistor and the capacitor assures that the capacitor is not charged improperly in the event the normal current conducting mode of the transistor is disrupted in the presence of large amplitude video signals, thereby preventing operation of the closed control loop from being disrupted.