914,254. Valve and transistor saw-tooth generating circuits. ASSOCIATED ELECTRICAL INDUSTRIES Ltd. Feb. 19, 1960 [March 3, 1959], No. 7385/59. Class 40 (6). A saw-tooth generator is coupled to an amplifier via an adding network, the waveform being linearized by feedback via a differenting and an integrating circuit to the other input of the adding network. The Specification describes frame deflection circuits for television receivers. In Fig. 1, the capacitor C 1 is charged via resistor R 1 and repetitively discharged by means of the oscillator V 1 . The saw-tooth wave so produced is fed via the left-hand part of potentiometer R 2 to the grid of the amplifier V 2 and thence via transformer T to the deflection coil SC. The effect of the inductance of transformer T on the linearity is minimized by a negative feedback circuit comprising a differentiating circuit C 4 , R 4 and an integrating circuit R 3 , C 3 , the latter circuit reducing the amplitude of flyback pulse fed back. The amount of feedback and hence the scan amplitude is controlled by variation of potentiometer R 2 , which acts as an adding network. Resistor R 3 . may also be variable. Fig. 2 shows a similar circuit using a transistor amplifier TS in which the base bias is derived from a potential divider R 7 , R 8 . The use of isolating resistors for feedback and input paths prevents faulty interlacing due to unwanted line pulses being fed back from the output circuit to the frame oscillator V 1 . Specification 479,113 is referred to.
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