Neutralization of Screen-Grid Tubes to Improve the Stability of Intermediate-Frequency Amplifiers

By a simple analysis it is shown that the grid-plate reaction in a screen-grid amplifier stage may be neutralized. This is accomplished by injecting into the screen circuit a small voltage opposite in phase to the plate voltage. Practical means for accomplishing this injection are described and a few of the obvious limitations are outlined. Even imperfect neutralization is claimed to be advantageous in improving the operating characteristics of high-gain-narrow-pass-band amplifiers. For numerous applications it is felt that the increased stability obtainable more than justifies the inclusion of the additional circuit components required.