| 摘要 |
1,214,791. Transistor sawtooth circuits; cathode-ray tube circuits. INTERNATIONAL BUSINESS MACHINES CORP. 7 Jan., 1969 [15 Jan., 1968], No. 860/69. Headings H3T and H4T. A C.R.T. deflection coil (81, 91, Fig. 1, not shown), is supplied with a ramp voltage a, Fig. 5, to which is added at its start a step voltage b which assists deflection of the beam and which terminates when the ramp terminates. The ramp a produces an X-deflection of magnitude AXa and a similar but inverted ramp d produces a Y deflection of magnitude AYa, and to each of these is added a rectangular pulse whose amplitude is respectively proportional to #Xa and #Ya and whose duration is equal to that of the ramp. The resulting signals c and f are applied to the coils and speed up the changes in beam deflection velocity at the start and end of a trace to prevent bright spots. The X and Y deflection signals are supplied in digital form #Xd and #Yd to an input stage (10) which derives the square root of the sum of their squares, and in unit (20) converts this to analogue form; a unit (30) produces therefrom a pulse 31 of duration proportional to the length (and time) of the desired trace (AB, Fig. 2, not shown). This pulse enables integrators (40, 50) to generate the ramps a, d; and also opens gates (41, 51) which pass #Xa and #Ya signals from d/a converters (42, 52) to operational amplifiers (60, 70) which add them to a and b respectively to produce the deflection waveforms e, f. The integrators each include a F.E.T. (45, Fig. 3, not shown) to whose source the #Xa or #Ya signal is applied and to whose gate the gating pulse 31 in applied; the drain is connected through a resistor (44) to an amplifier (46) having Miller feedback (47). |
