Low-Frequency Compensation of Video-Frequency Amplifiers

The low-frequency response of a conventional multistage plate-compensated video amplifier is analyzed in terms of the distortion of a square wave as measured by a rounding of the wave form. Design criteria are derived to give control of the amount of rounding in the initial design of the amplifier. Amplifier compensation effected by inclusion of a discrete impedance in the screen-grid circuit is discussed, and design formulae are derived. Comparisons of this type of compensation with that where compensation is effected exclusively in the plate circuit are made. The comparisons show that it is difficult to make a strong case favoring the adoption of screen compensation, except when direct coupling is utilized.