A Survey of the Limits in DC Amplification

The influence of a cathode temperature change of planar diodes and triodes is calculated with the help of extended Langmuir tables. The possibility of compensation of this temperature effect is considered. Two units with a common cathode sleeve show no conclusive improvement in cancellation of the heater effect. The disturbance voltage as a result of anode voltage changes is investigated. Some new compensating circuits are presented, resulting in dynamic and in-phase balance simultaneously for a single adjustment. It is found that for all balanced circuits the stability demand for the supply or auxiliary voltage is nearly the same. The change of tube "constants" with time and the relation between anode current and flicker effect attenuation is investigated. It was observed that the poorly defined position of the heater in the cathode sleeve seriously limits tube stability.