A transistor linear time-base circuit for a high-current electromagnetic deflection system

A time-base circuit is described that produces a linear saw-tooth current waveform suitable for driving the magnetic deflection system of a cathode-ray tube. The current waveform, which has a peak amplitude of 1 amp, is obtainable at a minimum sweep duration of 120 microsec and a repetition frequency of 2 kc/s. A linearity of better than 1% is obtainable. The circuit is a feedback amplifier of the Miller integrator type. The output transistor has a resistive load in its emitter circuit, and the feedback capacitor is fed from this point. A linear voltage saw-tooth waveform is produced across the emitter resistor, and the resulting linear current saw-tooth waveform flows through the deflection coil placed in the collector circuit. A transistor used as a switch in the feedback path sets the quiescent conditions, and this switch is opened for the duration of the sweep. The circuit uses germanium transistors and operates satisfactorily at an ambient temperature of 50° C. Compensation circuits are to reduce temperature effects, and a rise in ambient temperature from 15 to 50° C changes the time-base velocity by less than 1%.