The article below «Amplified Automa

The article below «Amplified Automatic Gain Control » was found in the October 1951 issue of the «Wireless World».This article fits pretty well to the examinations that Joe Sousa has shown in his post above.Its just a practically application about the EF50's dual control properties by using its suppressor grid g3 as second control grid. Amplified Automatic Gain Controlby using the EF50This article describes an amplified automatic gain control circuit which can be embodied in a t.r.f. or superheterodyne receiver and is no more complicated than circuits currently used for non-amplified a.g.c.; no additional valves or negative h.t. supply are required. An advantage of the circuit is that the controlled valves may be high-slope pentodes giving higher gain than is available from the variable-mu pentodes used in conventional a.g.c. circuits.The performance obtainable from the suggested circuit can be illustrated by the following measurements made on a t.r.f. receiver with a single controlled valve. As the input was increased from 100 µV to 0.3 volt, the output increased by less than 2 dB; in a typical 4-valve superhet with two controlled stages but non-amplified a.g.c. the output increases by approximately 15 dB for the same range of input signal amplitude.The circuit to be described embodies suppressor-grid injection of the control voltage. The application of a negative bias to the suppressor grid of a pentode produces markedly different effects from a negative potential applied to the control grid. The effect of varying the control-grid potential is to vary the total (i.e. anode + screen) current and the curve of total current plotted against control-grid potential is similar to that of a triode.