Architecture for a video preamplifier with an on-screen display
AssigneeNational Semiconductor Corporation
InventorRONALD W. PAGE
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Abstract
A video preamplifier having an on-screen display (OSD) capability uses one channel of an OSD input video signal to generate a blanking signal for blocking output of a video signal. When the blanking signal is asserted, the remainder two channels provide the on-screen display. The blanking signal is generated in a high speed mixer circuit including an emitter-coupled differential pair for amplifying the OSD input signal about an operating DC offset voltage and a pull down circuit for providing the blanking signal.
Claims5
An on-screen display (OSD) system, receiving an input video signal and an input OSD video signal, comprising:
- an input stage amplifying said input video signal;
- an OSD input circuit (i) receiving said input OSD video signal, (ii) detecting an active component of said input OSD video signal, (iii) amplifying said input OSD video signal, and (iv) asserting a blanking signal when said active component is detected;
- an output stage, receiving said amplified input video signal, said amplified input OSD video signal, and said blanking signal, said output stage providing said amplified input OSD video signal as an output video signal of said OSD system, when said blanking signal is asserted, and providing said amplified input video signal as said output video signal, otherwise.
Dependencies are inferred from the claim text.