D.c. controlled chroma circuit

Claim 2

In a color television receiver, a chroma controlling circuit comprising: a plurality of first circuit means for demodulating a modulated chroma signal having a blanking period, said first circuit means having an input for a modulated chroma signal, an input for a reference subcarrier, an output for a demodulated color difference signal, and a DC controlling means coupling a received DC signal and said demodulated color difference signal, so that the DC level of the demodulated color difference signal at said output is dependent on said received DC signal, said demodulated color difference signal being directly coupled respectively to a Power amplifier circuit for driving a color picture tube; a plurality of second circuit means for extracting respectively the DC level of each color difference signal over a portion of the blanking period, said second circuit means having an input for a color difference signal and an output for a continuous DC signal proportional to the respective extracted DC level; and a plurality of third circuit means for feeding continuous DC signals back to each of the DC controlling means of the first circuit means for demodulating a chroma signal, thereby maintaining a quiescent DC level at said output for the demodulated color difference signal at a substantially predetermined level.

Claim 3

A chroma controlling circuit as set forth in claim 1, wherein said second circuit means for extracting the DC level of each color difference signal includes; a switching element rendered completely conductive over a portion of the blanking period, a capacitor connected in series with the switching element, the series connected switching element and the capacitor being connected across an output terminal of a first circuit means for demodulating a chroma signal and ground, and the connection point of the switching element and the capacitor being connected to a high impedance input terminal of a third circuit means for feeding DC signals.

Claim 4

A chroma controlling circuit as set forth in claim 1, wherein said second circuit means for extracting the DC level of each color difference signal includes; a first transistor whose base is connected to an output of a first circuit means for demodulating a chroma signal, a second transistor to whose base a common DC level is applied, a third transistor to whose base a gating pulse is applied, and whose collector is connected to common emitters of said first and second transistors, and a capacitor connected across the collector of said second transistor and ground.

Claim 5

A chroma controlling circuit as set forth in claim 1, wherein said first circuit means includes; first and second transistors comprising a common emitter differential amplifier, third and fourth transistors comprising a common emitter differential amplifier, fifth and sixth transistors comprising a common emitter differential amplifier, a chroma signal being applied to the base of one of said fifth and sixth transistors and a seventh transistor whose collector is connected to the common emitters of said fifth and sixth transistors, in which the bases of said first and fourth transistors are common and a reference subcarrier is applied to the common bases of said second and third transistors, the color difference signal being produced on a common collector load of said second and fourth transistors, and the collectors of said fifth and sixth transistors being connected to the common emitters of said first and second transistors and the common emitters of said third and fourth transistors respectively.

Claim 6

A chroma controlling circuit as set forth in claim 4, wherein said third circuit means feeds a DC signal proportional to the extracted DC level back to the base of said seventh transistor.

Claim 7

In a color television receiver, a chroma controlling circuit comprising: a plurality of first circuit means for demodulating a modulated chroma signal having a blanking period, said first circuit means including a chroma demodulator and an amplifier directly coupled to said chroma demodulator and providing output signals, said chroma demodulator having an input for a modulated chroma signal, an input for a reference subcarrier, an output for a demodulated color difference signal, and a DC controlling means coupling a received DC signal and said demodulated color difference signal, so that the DC level of the demodulated color difference signal at said output is dependent on said received DC signal, and output signals of said amplifier being directly coupled respectively to a power amplifiEr circuit for driving a color picture tube; a plurality of second circuit means for extracting respectively each DC level of the output signals of said amplifier over a portion of the blanking period, said second circuit means having an input for a color difference signal and an output for a continuous DC signal proportional to the respective extracted DC level; and a plurality of third circuit means for feeding continuous DC signals back to each of the DC controlling means of each said chroma demodulator, thereby maintaining a quiescent DC level at the output of said amplifier at a substantially predetermined level.

Claim 8

In a color television receiver, a chroma controlling circuit comprising: a plurality of first circuit means for demodulating a modulated chroma signal having a blanking period, said first circuit means including a chroma demodulator and an amplifier directly coupled to said chroma demodulator and providing output signals, said chroma demodulator having an input for a modulated chroma signal, an input for a reference subcarrier, an output for a demodulated color difference signal, and a DC controlling means coupling a received DC signal and said demodulated color difference signal, so that the DC level of the demodulated color difference signal at said output is dependent on said received DC signal, and output signals of said amplifier being directly coupled respectively to a power amplifiEr circuit for driving a color picture tube; a plurality of second circuit means for extracting respectively each DC level of the output signals of said amplifier over a portion of the blanking period, said second circuit means having an input for a color difference signal and an output for a continuous DC signal proportional to the respective extracted DC level; and a plurality of third circuit means for feeding continuous DC signals back to each of the DC controlling means of each said chroma demodulator, thereby maintaining a quiescent DC level at the output of said amplifier at a substantially predetermined level.