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US 5,495,214 AGranted
Method and apparatus for controlling the operating point of an amplifier stage
AssigneeDeutsche Thomson-Brandt GmbH
InventorBernhard Malota
Life of this patent
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Abstract
At high frequencies, a video amplifier draws a higher current and normally is biased to provide such current. However, since high frequencies are rarely encountered, the present circuit controls the operating point as a function of the frequency. More specifically, a controlled variable which controls the operating point of the amplifier stage is obtained in dependence on the frequency to which the amplifier stage is driven.
Claims4
Apparatus comprising:
- an amplifier having an input and an output;
- a source of an input video signal coupled to said input of said amplifier;
- said video signal having trace intervals in which picture information is present and retrace intervals in which video information is not present;
- means for coupling said output of said amplifier to a load;
- a source of a bias signal coupled to said input of said amplifier;
- said amplifier including a first transistor having a first-input electrode, a second-output electrode and a third electrode, and arranged in a follower configuration;
- said first-input electrode being coupled to said input of said amplifier;
- said second-output electrode being coupled to said output of said amplifier;
- and said third electrode being coupled to a power supply terminal;
- a sensing element connected between said third electrode of said first transistor and said power supply terminal;
- and
- a feedback network, including a filter capacitor for developing a DC signal indicative of the current supplied by said amplifier to said load in response to said picture information represented by said video signal during said trace intervals, coupled between said sensing element and said source of said bias signal for modifying said bias signal as a function of said current.
9 more elements
Dependencies are inferred from the claim text.