| 摘要 |
<p>An automatic kinescope bias (AKB) control system includes a sampling amplifier (52) which provides an output current for charging and discharging a storage capacitor (56) in response to the amplitude of a derived pulse V1) representative of the black current level conducted by the kinescope of a television receiver. The derived pulse amplitude is greater than zero when the black current level is correct, and is applied to the amplifier via an input signal coupling path. During sampling intervals, an auxiliary pulse (Vp) is applied to the input signal path with a magnitude and sense for negating the amplitude of the derived pulse at the amplifier input when the derived pulse amplitude corresponds to the correct black current level. Accordingly, the amplifier conduction and the voltage on the storage capacitor remain unchanged. An impedance included in the signal path compensates for impedance variations at a sense point from which the black current representative signal is derived. <IMAGE></p> |
