. Electronic apparatus for biological research. Electronic apparatus and appliances; Biology -- Research. HT + HT- Fi^ure +25 and +40 V for the types of valve tested—Mullard EF37A and ME1400. The author has not tried this technique with pentodes, as a variable supply carried on the cathode is not easy to arrange. With triodes, however, it is not too difficult; the first method which occurs to one is Figure , but -« 9V grid-bias [ battery: taps every -!- 1V2V in t { HT battery: I taps every i 9V JL Figure this is not satisfactory. For correct operation, the resistance seen loo
. Electronic apparatus for biological research. Electronic apparatus and appliances; Biology -- Research. HT + HT- Fi^ure +25 and +40 V for the types of valve tested—Mullard EF37A and ME1400. The author has not tried this technique with pentodes, as a variable supply carried on the cathode is not easy to arrange. With triodes, however, it is not too difficult; the first method which occurs to one is Figure , but -« 9V grid-bias [ battery: taps every -!- 1V2V in t { HT battery: I taps every i 9V JL Figure this is not satisfactory. For correct operation, the resistance seen looking back into the network supplying HT to a cathode follower ought to be low; to achieve this the resistor values in the divider chain have to be so small that a current is wasted down them of a magnitude which is intolerable in battery-operated gear. A promising alternative is to feed the cathode fol- lower from another cathode follower {Figure ). In this case the output impedance of the variable HT supply to the lower valve is Ijg^ for the upper, and the potential-divider chain can have as high a value as is wished. However, in view of the extra valve involved, the method finally adopted is shown in Figure The required HT is selected to the nearest 9 V by 625. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Donaldson, Peter Eden Kirwan. New York, Academic Press
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