Clamp circuit for a color television receiver

Claim 1

In a color television receiver including a cathode ray tube having at least one control electrode, means for deriving periodic synchronizing pulses from a received signal, means for providing color signals and means for transmitting the color signals from the color signal providing means to the control electrode, means for establishing a first bias on the control electrode in the presence of the synchronizing pulses, and a second bias in the absence of the synchronizing pulses comprising: means for developing the first bias comprising a voltage divider including first, second and third resistive means, said voltage divider being coupled between a point of bias potential and a point of reference potential and developing said first bias at the intersection of said second and third resistive means; means for coupling the first bias to a control electrode of the cathode ray tube; means for developing a second bias; switch means operative to assume a first state in the presence of synchronizing pulses and a second state in the absence of synchronizing pulses for applying said second bias to said first resistive means in response to the reception of the periodic synchronizing pulses, said switch means being connected between the intersection of said first and said second resistive means and a point at the second bias and having a control terminal coupled to the means for deriving periodic pulses; and clamping means energizable in the presence of the periodic synchronizing pulses for periodically establishing a voltage upon said control electrode which is of substantially the same magnitude as the voltage provided in the absence of the periodic synchronizing pulses by said means for developing said first bias.