Abstract :
An oscillograph is described in which transistors are used throughout. The instrument comprises a vertical amplifier with a bandwidth of 0.5c/s¿25kc/s, a free-running time-base saw-tooth generator with a frequency range from 1 to 1000 c/s, means for internal and external synchronization of the time-base generator and several supply units. The 3 in cathode-ray tube is symmetrical, with electrostatic deflection. The input impedance of the vertical amplifier depends to some extent on the sensitivity, being 3 kilohms for a sensitivity of 15 ¿V/cm, 10 kilohms for 100 ¿V/cm, 500 kilohms for 5mV/cm and 1 megohm for all lower sensitivities down to 50 volts/cm. The output amplifiers for the final horizontal and vertical deflection voltages are of a novel design. The voltage output is increased by series connection of transistors, while an equal voltage distribution across the transistors is ensured by application of appropriate feedback. Two of these series arrangements are connected in an emitter-coupled push-pull circuit, which gives 400 volts peak-to-peak voltage at a supply voltage of 250 volts. With mercury cells the useful battery life is approximately 60 h. Emphasis is laid on the calculation of the output amplifiers and the matching of the source impedance to the input of the vertical amplifier to arrive at a low noise figure.
