Anti-flaring video output amplifier circuit and technique
US4825294A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Oct 7, 1987 |
| Grant date | Apr 25, 1989 |
| Priority date | — |
| Expiry date | Oct 7, 2007 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N9/648
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
An RGB video output drive amplifier is provided with current limiting circuitry at the base of the driver circuit. In a preferred embodiment, the driver circuit comprises a drive transistor with associated biasing circuits. The base of the drive transistor is coupled to a current limiting circuit to shunt excess current from the base of the transistor and to block additional input current at or near the level representative of the driver transistor reaching its saturation mode. Excess current is dissipated through associated resistance in the base circuit and while diode means prevent high input signals from driving the drive transistor into saturation. Maintaining the drive transistor at or below its saturation level pevents flaring in the resulting video picture display. No appreciable storage charge is built up during the short periods which the drive transistor may enter saturation in response to rapid transients provided through a transient response circuit in parallel with the current limiting circuit. Detail in the resulting picture is optimized and minimal additional capacitance is added to the output circuitry.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.