Output driver for a generic Geiger tube - a special gas tube designed to detect ionizing radiation. The tube is represented by the 6MOhm resistor and switch, which "closes" when a particle of ionizing radiation briefly closes a conducting path between the anode and cathode. 470K is an external output resistor. Diodes clamp the output pulse to low voltage, and it the current is boosted by the Op Amp and Class B output stage.
