Output Buffer Amplifier

The Output Buffer Amplifier stage is a common-base amplifier with the signal current-driven into the emitter. It provides the output sawtooth current signal to the Horizontal Amplifier and provides a measure of isolation between the Sawtooth Generator and the Horizontal Amplifier. The HORIZ DISPLAY switch connects to this stage to control the A sawtooth output in the various horizontal modes of operation. In the A and A INTEN modes of operation, the A sweep signal passes through Q1038 to the Horizontal Amplifier. However, in the MIX and B DLY'D modes, —8 volts is connected to zener diode VR1039 which sets the emitter of Q1038 at about -1.8 volts. This biases Q1038 off, preventing the A sawtooth signal from passing to the Horizontal Amplifier.

the sweep starts to run, the negative-going ramp is coupled through the base of Q1002B and CR1004 to the cathode of CR1011. CR1011 becomes forward biased and when the level at the anode of CR1011 falls to about +4 volts Q1012 conducts and Q1014 turns off. The multivibrator remains in this state until the sweep starts to retrace and the voltage level at the anode of CR1011 rises above about +4.5 volts. The resultant pulse at the collector of Q1012 is applied to Sweep Control IC U870 to terminate the sweep. The pulse at the collector of Q1014 is applied to the A Sweep Z Axis Logic Gate to blank the CRT at the end of the sweep.

0 0

Post a comment