A Wide-Band Amplifier

Author: J.B. Hoag

For the amplification of the signals from the photoelectric element of a television tube, an amplifier is needed which has nearly constant gain over an exceptionally wide range of frequencies, from low audio frequencies up to several million per second. These are sometimes called video amplifiers. The addition of small inductances in series with the load resistance tends to sustain the amplification at the higher frequencies by offsetting the losses due to the effective input capacity of the next tube. In addition, a resistance is not uncommonly added across a tuned coupling circuit in order to broaden its resonance curve. A coupling unit, as shown at R₁C₁, Fig. 25 E, is sometimes used to sustain the lower frequencies.

FIG. 25 E. Coupling unit in a wide-band amplifier. See Proceedings of the Institute of Radio Engineers, Vol. 29, page 261, May 1941