Dynamic focussing circuit for TV receivers - has diode clamping circuit preventing alteration of static focussing setting

摘要

The dynamic focussing circuit, for television receivers, does not change static focussing when being set. A clamping circuit (D1, D2, R3) is coupled to an addition circuit (R1, R2) to which the parabolic signals are fed and which holds the sum signal corresponding to the centre of picture potential constant. The clamping circuit consists of two antiseries diodes connected at one end to reference voltage and at the other to the outputs of the vertical and horizontal generating circuity. The junction between diodes is connected via a resistor to a bias voltage.