Patent ID: 6512553
Filing Date: 2003-01-28
Classification: G09G,H04N

Abstract:
A single-channel video preamplifier circuit that receives an analog video input signal representing one of a plurality of color input signals, each color input signal corresponding to one of a plurality of video signal channels, the video preamplifier circuit comprising:(a) a video amplifier input stage circuit that includes (i) an input amplifier that amplifies the video input signal to provide an amplified input video signal; (ii) a contrast attenuator that attenuates the amplified input video signal in response to a contrast attenuation control signal to provide a contrast-attenuated input video signal; (iii) a drive control attenuator that adjusts the contrast-attenuated input video signal in response to a drive control signal to provide an adjusted contrast-attenuated input video signal; (iv) an output amplifier that receives the adjusted contrast-attenuated input video signal and a limiting signal as inputs and provides a limited DC offset video signal; and (v) a feed-back controlled current source that provides the limiting signal to the output amplifier; (b) a clamp comparator circuit that receives a clamp voltage at its non-inverting input and an amplified output signal at its inverting input to provide a clamp comparator output signal that controls the feed-back controlled current source of the video amplifier input stage; and (c) a video amplifier output stage that receives the limited DC offset video signal as a first input signal and an OSD color signal as a second input to provide a video output signal, the limited DC offset video signal being blanked in response to assertion of the OSD color signal.