CIRCUIT FOR ACCURATELY EXTRACTING THE SYNCHRONIZATION INFORMATION CONTAINED WITHIN A COMPOSITE VIDEO WAVEFORM

• Main Authors: SCHLOTZHAUER, KENNETH G, ROTH, STEPHEN A
• Format: Patent
• Language: English; French
• Published: 16.12.1980
• Subjects: BASIC ELECTRONIC CIRCUITRY; CONTROL OF AMPLIFICATION; ELECTRIC COMMUNICATION TECHNIQUE; ELECTRICITY; PICTORIAL COMMUNICATION, e.g. TELEVISION

CIRCUIT FOR ACCURATELY EXTRACTING THE SYNCHRONIZATION INFORMATION CONTAINED WITHIN A COMPOSITE VIDEO WAVEFORM A circuit for accurately extracting the synchronization information contained within a composite video waveform includes a means for establishing the back porch level of the waveform to a first voltage through a first feedback loop, a means for establishing the sync tip level of the waveform to a second voltage through a second feedback loop, a means for providing the extracted synchronization information at a time determined midway between the first and second voltages, and a system which achieves these ends. An automatic gain control amplifier is included as a portion of the circuit within the system and whose gain is linearly proportional to the logarithm of the AGC voltage and wherein changes in AGC voltage do not interrupt the DC potentials within the amplifier nor do DC changes change the gain of the amplifier.